Options to move the school rucksack during the trip If to commute to school by bike, how is the school rucksack usually transported? I can see the following options:

Keep it on the back. It is quite heavy, gravity center will be high and in case of falling over head it may add to the injury.
Put into basket above the rear wheel. The form of the usual rucksack does not fit well to secure it from falling.
Use specialized bicycle container for luggage. But the models I have used so far are time consuming to remove and not adapted at all to carry on hand when full.

Are there special equipment for that? Which approaches are usually taken?

I've always commuted to school (and subsequently to work) by bike, and my method was: none of the methods mentioned in the question.  I'm from The Netherlands, and grew well into adulthood (and lived in other countries) before I realised that arriving to school like this is not the norm in most of the world.

I had permanently attached to my rack a set of heavy-duty luggage straps, then I would attach my backpack to this.  I think the straps were actually attached at the axle, so it would have required some tools to remove it.  My backpack was usually secure from falling, although it occasionally did fall or topple to the side, then I would stop to reattach it.  From memory, I think that happened less than once a month in a 20 km/day round trip commute.  I did not own any panniers at the time.  I have fallen off my bike once during around nine years of commuting to school by bike, while turning on an untreated icy surface, the luggage did not add to injury.

Later I got some Dutch-style panniers that I also left permanently on my bike.  I would put my school backpack inside one side of the panniers, and take out some books to put loose on the other side to balance the weight.

Most of my classmates simply cycled with their rather heavy backpacks.  At the time there was a fashion to have the backpack extremely low, with extremely long shoulder straps.  Some kids would have backpacks hanging as low as their knees.  I remember seeing kids with their backpacks so low, that the backpack would actually rest on the rear luggage rack as they were cycling.

I think a pannier/backpack-combination is both a poor pannier and a poor backpack, and when it's heavy it makes for an imbalance bike too, unless you can somehow convert a single backpack into /two/ panniers?


Shimano Front derailleur I am rebuilding a Trek 2005 model 6500 and my spec. sheet for the bike says it has a Shimano Alivio front derailleur.  Where do I find the model no. that should be stamped on the part? I don't see it anywhere on the part.  This is a 3 x 8 speed setup.

Thanks,
Jerry

You might have a hard time finding the exact same part that was originally on the bike. However, front derailleur is a pretty standard piece of kit and you can replace it with compatible.

Things you need to look for when buying front mech:

Road and MTB FDs are different
Shimano and SRAM FDs work with the others shifters (which is different for RDs)
Seatpost clamp diameter - size of the tube the mech is clamping around (Shimano FDs often come with shims but SRAM FDs do not)
If the mech is top pull or bottom pull: the cable comes from above the derailleur (top pull) or below (bottom pull). Dual pull derailleurs work either way.
There are 3 clamp positions: high clamp sits above the mechanism, low clamp is at the same level of the mechanism and e type is on a frame which sits between the bottom bracket and the crankset.
Make sure the new mech is 8 speed. 9 speed-mech won't work with 8 speed chain, as the chain widths are different.


How much does tire pressure affect the weight of the wheels Kind of inspired by this question, but something I've been thinking about for a while.

How much does the air in a bike tire weigh?  Is it an appreciable amount? Is there a point where using a wider tire, like at 28c at 80 psi would be lighter than a 25c tire at 100psi? Obviously, this depends on the specific tires used.  I don't have a scale precise enough to measure, and I don't have the math/physics knowledge to figure this out.

The ideal gas law (which is a good approximation in this case) says PV=nRT where P is pressure, V is volume, n is mols of gas, R is the ideal gas law constant, and T is temperature in Kelvin.

Thus, solving for n, we see n = (PV)/(RT). Then, assuming air is made up of {gas1, gas2,...} with fractions {p1,p2,...} (so p1+p2+...=1) and corresponding molar masses {m1,m2,...}, the mass of air in a tire is (PV/(RT))(p1*m1+p2*m2+...). So, what we see is that the mass of air in a tire is directly proportional to the volume of the tire and directly proportional to the pressure in the tire, and inversely proportional to the temperature of the air in the tire.

We will make the following (reasonable) assumptions: Assume the temperature is around room temperature (293 Kelvin) and the volume of the tire regardless of pressure is the same (primarily determined by the shape of the rubber, assuming not severely under/over inflated). For convenience, air is about {nitrogen, oxygen} with {p1,p2}= {0.8,0.2} and molar masses {28 g/mol,32 g/mol}. Thus, under these assumptions (V is fixed, and T is fixed), the mass of the air in tire grows linearly with pressure.

So, the mass of air in a tire of volume V and pressure P and temperature T is about (PV/RT)(0.8*28+0.2*32) grams. It may be better to write it as "P ((V/(RT)) (0.8*28+0.2*32)) grams" noting that V/(RT) is a constant for us.

Since I don't want to put the units into wolfram alpha carefully, you can put in the entry "(7 bar* 10 gallons)/(ideal gas constant*293 Kelvin)*(0.8*28+0.2*32)" and read the result off in grams (ignoring the unit it says there) to get an estimate for the weight of air in a 7 bar (~100 psi), 10 gallon volume tire as around 313 grams. Is 10 gallons reasonable? No.

Lets be crude about estimating the volume of a tube using a torus. The volume of a torus is V=(pi*r^2)(2*pi*R) where R is the major radius and r is the minor radius. Google will calculate it for you (and has a picture of what major and minor radius is).

I can't be bothered to actually go outside and measure these things, but lets be crude and use a massive tire. Say the minor radius is 2 inches, and the major radius is 15 inches (this is probably larger the size of the tire on something like a Surly Moonlander). This has a volume of about 5 gallons. If you were a nutcase and running this at 7 bar, it would be around 150 grams of air. At a more reasonable 1 bar or 2 bar, youd be at 45 or 90 grams.

What about a thin road bike tire? Lets also assume the major radius is around 15 inches, and the minor radius is around a half inch. Thats around 0.3 gallons of volume. Plugging into our formula, at 7 bar, we see that this is about 9 grams. At 10 bar, a whopping 13.5 grams.


What are the strengths, weaknesses and/or recommendations for a BLB Mosquito Saddle? I ask this here because I couldn't find too much information or reviews about BLB Mosquito saddles. If administrators find this question doesn't fit into this place, please feel free to remove/edit this question.

So I'm about to order a 'Tan' version of a BLB Mosquito saddle (from London to Bogota, that saddle will travel too much far I've traveled in my entire life). I fell in love with it because its style and color (it suits perfectly with my bike, a somewhat customized GIOS Torino Pro '86); since having a BLB handlebar, I feel BLB is doing a very nice work with their products. I have to say I felt somewhat tempted to get a Brooks saddle because of their reputation thing, but I didn't liked any of them (too much fancy for me, and they're very expensive) so I decided to get the BLB one (it happens to be inspired by Brooks saddles).

Along with it, I'm ordering a Velo Orange long setback seatpost. I guess I won't have any problems using that BLB Mosquito saddle with that seatpost, but just in case I ask here if someone have had any experience with that seatpost.

Getting to the point: since I commute about 2 hours/day (40 km/day, 200 km/week) and I'm riding with a old, cheap, wider and doesn't-even-have-foam-inside saddle, do you think it's a good choice going for the BLB one? Do you have any recommendations for its usage or keeping its leather in good look? Thanks in advance!

Looking at the BLB Mosquito it is marketed as a "race" saddle which in the world of leather saddles seems to be short hand for narrow with the expectation that your cockpit setup has lots of handle bar drop (handle bars below saddle). Depending on the width of your sit bones, these saddles can be uncomfortable in a more upright position, as I have learned.

BLB Mosquito Race - side view

Brooks B15 Swallow

The BBL Mosquito also looks remarkably similar the Brooks B15 Swallow saddle.

As an owner of a B15 I can must advise you to carefully consider this saddle decision as it is really designed for race bikes. I am relatively average in stature and on the lighter side for weight.  I found this type of saddle was only comfortable in a racing position (i.e., 5-10 cm of drop on the handle bars).  Anything higher and my pelvis would rotate enough that the my sit bones would strike the metal rails.

Now everyone's anatomy is different, including sit bone width.  But for more general applications and for a more diverse array of body types, I think you should consider a wider saddle such as a Brooks B17.  Either that or measure the width of the BLB and compare it to the Brooks B17 to ensure the saddle is a bit wider.

As far as build quality, I haven't the foggiest about BLB!

Leather Saddle Caveat

Most seem to be drawn to leather saddles for their looks. I am so-so on the looks, and a much bigger proponent on the comfort, once you choose a model that is appropriate to the application.  This is where all the marketing speak has let us down.  The descriptions on  how the saddles can be expected to fit is basically non-existing.  This is unfortunate as the saddles can be quite uncomfortable for some application/body type combinations due to the fact the saddles work as a hammock and use a solid rail.

This is where modern saddles can be better as they can be expected to provide adequate comfort to a larger array of body sizes due to the use of padding. That said, once you get the kinks worked out, in 15+ years of competition and 20+ years of cycling, I have never found a more comfortable solution.


Buying cheap now or saving for later? I have been thinking of getting back into cycling after a long hiatus and need to buy a bike. Is it better to get a cheap bike now and build up strength + get a feel for what I want in the future OR take a bit more time to save for an entry level good bike (I have my eye on a Specialized Crossroads)? My goal is to commute about 9.5 miles over paved but hilly terrain.

Get something now. Winter is coming…

Seriously though, if you don't have a good feel for what you want in a bike, buying something used that seems close will get you on the road and start you developing the experience you need to decide what you really want.

There are so many variables of fit and gearing that it will be hard to get it right the first time (at least that's been my experience, both with my own bikes and with helping friends and family pick bikes). Add to that commuting and getting back in shape and I think you'd be way better off buying whatever seems best now on craigslist and using it to help you sort out what you really want. A few months into it you'll be in better shape and have some real life experience to guide you in picking your next bike.

Finally there are things you may not have thought of that can make or break a commute – decent lights, riding clothes, a way to carry your gear – that will all add to the cost. Better to spend as little as necessary and have money on hand to add to your kit as you learn what you need to enjoy commuting on your bike.

Wait! There's one more thing… If you buy a relatively decent used bike the value won't change too much over the next 6 months or a year – especially if you take good care of it. So if you decide it isn't the right bike you can get a good portion of what you paid back when you sell it. This will be less true if you get a new bike and then decide to either sell it or start upgrading components.


In road racing, what are "rolling attacks"? Rider_X referred to rolling attacks in an answer to this question. What are they?

"Rolling attacks" are a series of sequential attacks on the peloton by typically a team or a group of riders acting as a team.  R. Chung covered this nicely in the comment section, but I will expand a bit here.

Typically you get two or three groups of riders  together to orchestrate this (where a group may consist of one or more riders).  The first group launches an attack (preferably when there is a lull in the peloton after a recent hard effort - gotta make it hurt to respond). They will either escape or the peloton hunts them down.  The exact moment the first group is caught, the second group launches another attack.  The moment they are caught the third or first group (depending on how many groups of riders you have) launches an attack. You then keep repeating as necessary or logical.

The idea behind doing this is that typically only a few riders (often tasked with this job) hunt down the breaks.  If you have the manpower, by doing this you are working to wear out the other teams by brute force. Eventually, if you are lucky, the peloton may decide not to respond and you have yourself a break or you have tired out key players on the other teams.  Again this only really works if you have a manpower advantage, leaving a few riders who are never involved with the attacks to conserve for the sprint or some other similar strategy.

As a caveat, I will add that I am not certain how much this strategy shows up in big shows (such as the Tour de France or Tour de Giro) as they know so much about the capabilities of the various riders, but I saw this was fair bit in our local racing scene.


Do specification sheets for older Shimano components exist? You can find official Shimano spec sheets on their website. They reach back to the year 2004. Do older spec sheets from the 80s and 90s exist?

Yes they do.
They way Shimano did it for a very long time (I don't have the date range) was that each model of component released had two different documents released for it, which were Shimano's primary means of communicating technical specs to the world. These were the "SI" (Service Instructions) and "EV" (Exploded View) documents. The SIs contained throwaway legalese, setup instructions, and compatibility type information, for example total capacities and max large cog numbers on a rear derailleur, or recommended spindle length for a crank. Sometimes the compatibility type information you need is actually hiding on the EV, especially when what you're trying to figure out is a small part number, i.e. for cross-compatibility parts ordering type purposes.
The EVs still exist in the same form as ever, but at some point (again I don't recall the year), they stopped doing SI documents and instead now do the UMs (User Manuals) and DMs (Dealer Manuals) found on si.shimano.com for the procedural and cautionary/legalese type content, and their spec tables for compatibility information.
As far as I know, the 2004 date you mention was the beginning of Shimano releasing spec data in table form. SIs were still around then, so in this period both types of document were released and had some of the same information. For parts not covered in those archives, the main source for that kind of data is the SI documents. There are some entities out there who have taken it upon themselves to archive them for the public, and a lot of those dating pretty far back in time can be found by searching the model number plus "si". Shimano has also added some older SI documents to their own site.
Prior to the Dealer Manual PDFs, their current form of communicating core procedural information, there used to be yearly paper "STI Guides" that dealers got. It was a maddening and backwards system because there was some technical material in them that wasn't available anywhere else, but getting old ones was difficult, and so was finding what you needed even if you did have a huge stack of them. They were also the source of compatibility charts akin to what's in the Compatibility section of si.shimano.com now. STI Guides persisted well into the internet age, but I'm not sure when the last one came out.


What size hub do I need for a Giant Escape 2 (2016)? As I mentioned in a previous question, I'm in the process of replacing the stock rear wheel on my Giant Escape 2 (2016)(any comments/answers related to why and whether I need to replace it should be entered there). The one thing I can't seem to find in the specs is whether I have a 130mm or 135mm wide wheel/hub/or whatever that measurement pertains to. How do I find out? How do bike shops know? If I measure this myself, what do I actually measure--the rear wheel dropouts or something else?

The measurement there is known as "O.L.D." or Over-Locknut Diameter.  It's the width of the opening in the frame between your dropouts, with a hub installed.  So from outside-of-locknut to the opposing side outside-of-locknut on your hub.  This can be measured with calipers or (more difficult but possible) with a ruler.  Remember in this case you need to be very accurate in measuring, since it's either 130 or 135 millimeters, and that 5 millimeter difference is very small(about a quarter inch).  If you're sure about the type of bike you have, this could be an easier way.  130mm hubs are generally only used on true road bikes(700x~20-25c).  135mm is used on Mountain or Hybrid bikes(any 26", 29", 27.5", or 700x~30-50c).  Looking at Giant's website, this should be a Hybrid, and 135mm OLD.


Repairing center-pulled brakes My bike has the old center-pulled brakes. Unfortunately the ropes for both brakes (front and back) broke, and I had to replace them. Now the small helper-ropes have no friction anymore on the main rope, resting on the mudguards, and providing almost no pulling power for the second brake. Why do the new ropes not provide friction anymore (aka are too thin), and how can I fix that?
Edit: Photos:

Brake cable should go through gap in a screw, that is locked with a nut to the holder, connecting cable pulled by the lever with, as you called, helper. Sometimes a gap for the screw in holder is not circular. If you mis-oriented screw against the hole in holder, it rests outside the hole and does not tighten the cable.

Please, add also the photo of the screw that holds brake cable on the brake arm.
It looks like you have to unscrew that screw, pull more cable and then tight it. Also put a bit of oil on the cable where it goes through circular element.

I strongly advice reading article on adjusting cantilever brake. In short:

unscrew adjusting screw on the brake lever housing by 3 turns, secure it with nut.
unscrew brake pads holders, push the pads towards wheel as far as possible (this will increase braking force), tighten it a bit
unscrew brake cable holder on the brake arm, pull it as far as possible - pads should touch the rim. Tighten the screw.
Adjust pads that they are adjacent to the rim, tighten them
screw adjusting screw mentioned in pt 1 back.

adjust brake arms position witk screws on the bottom of them.


Hydraulic brake cable invisible leak. Possible? I've crashed hard, handlebar rotated as much as it could and I guess rear brake cable was stretched. Braking became soft. Time to bleed I thought.

But I'm completely unable to bleed it. Tried some many times w/o any success.

To test my bleeding techniques I've rebleed other (front) brakes - everything is fine. Even tried to push air first and then fix it by rebleeding. Works perfect.

Then I've tried to move parts of working brakes to non-working brakes and bleeding each time. Turned out that the fail point is cable (hose).

However I don't see any leaks or damages. At all.

Brakes: Avid Elixir 3 and it uses DOT fluid.

Is that possible for the cable to have some sort of invisible internal leak?

Generally speaking it is possible. But you should also make sure that the pistons on the rear caliper are not pushed out too much which could lead to possible oil leak, usually but not necessary when the brake pads are too worn (say less then 0.5mm). I had lots of leaking problems with one of the Shimano brakes in the past, and like you I couldn't identity the problem.

You could start by replacing the brake hose with the new one, which should help narrow the problem. Other than that the canister cap on the brake lever knows to give problems sometimes. Make sure the cap is well tucked in in the right place, also don't forget that there is usually a small piece of thin rubber between the canister cap and the lever which also stops oil going out. One more major thing that can also go wrong with the lever is the small piston below the thing you actually press to brake. One piston pushes the oil from the lever, and the other two pistons (or four in same cases) push the brake pads.

Maybe the best way the determine where oil leaks is to fill the system with new oil, push out the air if there is any and leave it a couple of days to sit like that, but also wrap some toilet paper tight around places that could possibly leak oil, around both hose ends, canister lever and piston and caliper and inspect the t.paper every couple of hours for oil marks. It may sound silly but can actually help.


Why is there so much friction on my rear wheel? With the chain detached, when I spin my rear wheel it slows down really quickly (2 turns?) as if the brakes are lightly on.  The brakes are well clear of the wheel though.  Any idea what it might be?  The bike is about 2 years old and I have not done any maintenance to the bearings, so I'm wondering if that might be it.  But I have no idea if those are really the symptoms.

Possible options could be

Damaged bearings
Bearing closed too tight
Bent axle
Spoke that touches the axle (I had it once when I put a straightened j spoke instead a straight pull one).


When Mark Cavendish says he's sprints at 1500 watts how long is that for? In an interview with Cycle Sport, Cavendish said he puts out over 1500 watts of power.

  “You’d be surprised at my watts,” Cavendish says.

  “Most people who say that their maximum is 1,600 watts won’t put out
  1,600. My maximum is 1,580, and that is a lot. Not many guys will do
  more than a hundred more than that. But no one will ever get close to
  that in a race after 200 kilometres,” he continues.

  “I put out 1,490 today in training, on bad form, but I won’t put that
  out in a race. It’s not watts, and it’s not just my frontal area in a
  sprint. It’s everything beforehand. How I ride in the peloton. My
  pedalling action. How I sit. I save so much energy for the finish.”

Is it 5 second power or 30 second power?

That kind of power is going to be between 5-30 seconds, and is most likely a 5 second maximum, or he's quoting the absolute peak that he put out.

There is a very interesting analysis of several Team Columbia riders from a couple years ago when Cavendish won the stage. A few riders have 30-40 second pulls at the front in the 650-700 watt range, and in the leadout, Markus is at 700+ watts for over 30 seconds with a peak over 1000.

So if the leadout is at 1000, Cavendish probably is doing 5-20 seconds in the 1200 range as he comes around the slingshot, with surge peaks into the 1400 range, but that level is not sustainable. You can see this when sprinters mistime their sprints and start losing steam short of the line.

Here is the link with the powerfiles.


Aluminium "white rust" on roadbike. How bad is my situation? After some research I did not find similar photos/examples to mine so decided to ask.
Recently I have bought used aluminum road bike. I did check all other parts and they are in good condition, but forgot to flip it and when I did I found this:

So my questions are:

How bad is this?
Can I stop it from spreading?

It’s not bad, it’s cosmetic only. It’s just surface corrosion that’s got under the clear coat. Do you live in area where salt is used on the roads? Perhaps the previous owner was not good about cleaning under the bottom bracket shell.
You can halt this by making sure to thoroughly clean the bike regularly and use something like WD40 in vulnerable area to displace water and provide a protective film.


Ultegra R8020 STI shifter sticking I have an Ultegra R8020 lever and I recently did a cable change. Everything worked fine for a few moments then on the first ride the left shifter wouldn't click up into the big ring. After a few attempts it crunched into place. After investigation I found that if you ever so slightly touch the paddle to shift down gear then the upper shifter will not work. This isn't the same on the right hand shifter which shifts fine.
I've taken the lever and hood off, degreased, greased and it works slightly better, but it feels like a mechanical issue instead of dirt or grit stuck in there.
Are there any tips on how I could rectify the problem? The shifter was in otherwise good condition before the cable change. It is nothing to do with the derailleur or cable, I can confirm its the shifter that is sticking.
Thanks for your help,
Brad

It’s possible the shifter mechanism has some material in it that is obstructing the proper operation, maybe a bit of wire from the cable, maybe dirt or grit. Unfortunately it may also be that something broke in the shifter.
You’ll have to systematically track down the issue. I’d start by removing the cable completely so you can check for damage to it.
Next, work the shifter without the cable installed just to check that the leavers are not jammed.
If the cable was not damaged re-thread it through the derailleur and out of the housing on the handle bar, or even the back of the shifter without going through the housing if you can manage it. Make sure the cable head is seated in the shifter properly. Put a little tension on the cable and work the shifter to check it’s operation. You may be able to get a better sense of what’s going on with it.


How do you spot the left side pedal on egg beater pedals? I've just got a new set of crank brothers egg beater pedals and I can't tell which pedal is for the left side, and which is for the right just from looking at them.  Is there an obvious way to tell without simply trying to screw them in?

Update: There isn't an obvious L and R that I (or another pair of eyes) could see.  The only text I could see was really fine print that mentioned the torque to put the pedals in.  I couldn't see anything in the instructions that appeared to say which one was which either.

This is from the Crank Brothers pdf available on their site or in the package:

  Eggbeater pedals have either a 6mm Hex, an 8mm Hex, and/or 15mm wrench flats.  Note that the right pedal has a
  standard right-handed thread and the left pedal has a left-handed thread.  For identification, left pedal has a small
  “L” on the spindle or a small groove around the spindle flange.  The right pedal has a small "R" stamped in the
  spindle or no special markings.

In my case there was no "L" on the spindle, but there is a small groove around  the left spindle flange.

The link: http://www.crankbrothers.com/support/product_documentation/instructions_eggbeater.pdf


Lockring tool seems to be 1mm or 2mm too small to fit sram 8 speed cassete? I'm trying to replace a cassette. I got a chainwhip tool set + two lockring tools. I assumed it would be compatible as it's a 'common' 8 speed cassette from sram.
However after trying this yesterday, the lockring seems a tiny bit too small (though all the grooves seem to line up. But it won't budge with the nut going through the lockring. I even tried to gently hammer it in, but that just left a 'hexagonal' marking on the lockring...
Potentially I need to remove the nut? However there is very little contact area (a few mm) that could occur between a spanner and the nut, unless perhaps it'll come off with very little force (I could give this a try tomorrow).
I did find this thread that seems to mention a similar problem: Is this an unsuitable cassette lockring tool?
However it's not clear in that question on how to determine one from the other?
My main question here is:

What lockring tool do I need?
Do I need to remove the nut?

Actually, this is starting to make sense. In the question I linked, it seems likely that they had a freewheel, and their lockring tool was too BIG. In my case I have the opposite problem, but it seems I have an actual cassette rather than a freewheel. In which case my lockring tool seems to be for a freewheel rather than a cassette..

The tool you have looks to be for freewheels. Here’s a photo of a known good cassette tool (Park Tool FR-5.2):
See how the splines are way deeper than your tool’s?
The other large tool you have is likely a bottom bracket tool and is not for cassettes at all.


What type of shoes should I get with regular pedals I have never been more than a casual rider, maybe 5 miles at a time. I signed up for a 500 mile multi-day bike event that i need to train for and was thinking about getting real bike shoes due to more energy transfer to the pedals. I just have regular simple platform pedals now. so would it even make sense to get special shoes with hard soles if I don't have regular pedals?

Thanks!

I like downhill larger platform pedals with what is commonly referred to as street shoes.
I don' like advertising a brand but an example is the best answer.
All Mountain Flats

You have people advising clipless (spd) and I don't agree.  Ironically clipless means the ski boot type clip in.  But I don't agree with spd.  I would do a 500 mile multi day ride on some big platform downhill pedals with the little spike and some and some nice street shoes.  There is enough traction to hold your foot in position.  You can move your foot around a little bit to change how you hit muscles.  I will ride an uphill is a little different foot position.  When you get off you can walk around and loosen up you legs.  You don't have to carry another pair of shoes or sandals.  Now a one day 100 mile ride - then I would ride spd.


Will driving through heavy rain with bike on my car damage the bike? I'll be driving for 4 hours with my bike on the rack through heavy rain. Will this damage the bike?

The prevalent thought among many members of the Cycling Illuminati (trademark) is that the high vehicle speeds will drive rain into your bearings on a bike if it is mounted to the roof rack. Seems kinda plausible, but here is a GCN video about how hard it is to actually drive water past seals and into bearings with a pressure washer:

Should You Jet Wash Your Bike?

  Spoiler: It took them a long time, with the pressure washer jet focused directly on the bearing itself at point blank for 3+ minutes to finally drive some water past the seals.

Unless you are traveling down the Autobahn at top speed with your bike mounted to a roof rack you hyper-car, you will probably be just fine.  Pressure washer water velocity is about 243 mph (391 km/hr). A Bugatti Veyron 16.4 Super Sport is the world's fastest road legal production car with a top speed of 431 km/hr (268 mph).  Technically, if you had a  special rack designed for your Veyron (wouldn't want to upset the handling at 400 km/hr), you might be able to generate enough velocity for this to be a concern. Even then, it is likely only the head set bearings (or maybe bottom bracket if you have external bearing version) that will take the brunt. Even then, these bearings are oriented in a plane perpendicular to the plane of motion (which will greatly reduce the velocity of the water that actually interacts with the bearing seal face).  Plus, don't forget that the front wheel usually rides inside the car and the rear hub is left on the bike, but will be running in disturbed air, which will further reduce the force of the rain water.


Crank axle cracked on 1972 Centurion, looking for guidance on how to replace As I said, I have a 1972 Centurion. Today while riding I hit a pothole as I was coming down on my left pedal. I immediately felt like my pedal was moving around in ways it shouldn't. Stopping to look, I'd cracked the actual axle that the crank arms attach to.

I'm looking for information on where I can buy a replacement part for this, how much it will cost, as well as how to carry out the replacement.

Here's the actual crack:

Here's the pedal looking all bent:

The crack is in the bottom bracket(BB) axle. This will at least need to be replaced. If the crank arm(silver part) is not damaged this can be reused.

There are many types of bottom bracket standards but it is most likely this frame has a 68mm English thread square taper bottom bracket which are the most common in pre year 2000 bikes.

Something like a Shimano UN26. Any bike shop should be able to supply and fit a new bottom(price in my local area would be $30-50 supply+fit). You do need specific tools to remove and fit bottom brackets so unless you plan on investing in some tools I suggest get a shop to replace it.


Why would a tire be for trainer use *only*? Yesterday I installed a Continental Hometrainer Tire on the rear of my CX bike (which had been purchased mostly for trainer use and which came with knobby tires unsuited for that purpose). To my surprise, the sidewall of the tire is marked "for trainer use only, do not use on road."

Beyond potentially getting them dirty, is there any risk to using such tires on the road?

Turbo trainers are notorious for quickly wearing out tires. Trainer tires are therefore made of a hard wearing compound. However, this compound may not provide enough traction for safe cycling.

Traction is immensely important as it is usually the limiting factor to the maximum speed in curves. If one's rear wheel slides away while cornering recovery is usually not possible.

See also the related question: What kind of tire should I purchase for use on a bike trainer?


Can I pedal my bicycle backwards to move it backwards? Is there any changes I could do to my cycle so that I can make it move backwards?Just a question out of eagerness.

To sum up all the comment answers, which provide you with a wealth of options:

The backwards bike
Retro-direct gearing
The Tri Via gearing system

Some parts of these look rather easy to fabricate such as the idler arms or connecting two forks together. The rear hub is going to be the most difficult part since you have to build two sets of engagement together and fit it in the space of a regular hub.


How many chain links do I need for my chain I have a 2017 DaVinci Django mountain bike and I am planning to upgrade my cassette to a 11/46 from 11/42. I would like to buy a new KMC chain. How may links do I need?114 or 116? Maybe it’s a different number. Can you help?

Generally, you would buy a chain that is "long enough" and then shorten it to the correct length. If you're adding 4 extra teeth, then presumably you would need at least 2 extra links from what you currently have. Look at Sheldon Brown's chain length article for determining the correct length.

  The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that one complete link (one inch, -- one inner and one outer half-link) overlaps. In almost all cases, this will give the optimum length.


Is it possible to pair wheel sensors with an Android phone GPS? This is a 2 part question:

I have concerns over the general accuracy of a GPS device to calculate speed. Mainly because I will be using the device in Eastern Europe, and not sure on the accuracy of the coverage.
Because of this concern I was thinking of pairing an android based gps app to wireless sensors mounted on the wheel, much like you would do with a Garmin 800.

I'm looking for the following reply:

Is my concern justified, or will a phone based GPS be accurate enough to give me a realistic speed indication?
If my concerns are justified, can you recommend some ways to pair the wheel sensors with apps?
What general features should I look for in a phone to bring out the best of it for use as a cycle computer / gps.

Thanks in advance!

The wheel sensor add on will do quite a bit to improve the accuracy of the GPS based current speed. The distance will generally be accurate, to within error values of 50 meters, or so depending on hardware. Most phones, especially with android, are on the lower spec of GPS design, using wifi databases and cellular triangulation to augment the GPS positioning sensor.

They generally use open source maps, like Google Maps, which often change, and are less than consistent about coverage. I would recommend using an ANT+ add on, if you are concerned about exact speed and distance.

Wahoo makes decent ANT+ sensors for the iPhone, but I'm not aware of a quality set up for android. There are too many devices, so it would be difficult to create a single device guaranteed to work across the board on android, even with the same OS version. I assume this is why they haven't made an Android version yet.

Hope that helps.


Kona Dr dew - drop handlebars So I have a kona Dr dew which is technically a hybrid. More road bike than mountain. I've only had this bike less than a year but I really like the look of it but I want to install drop handlebars. I understand this will also mean I will need to change the brakes and shifters. Anyone know a good reasonably priced set up I could use?

Here's the spec of the bike

FRAME MATERIAL  Kona 6061 Aluminum Butted
SIZES   46, 49, 53, 56, 59, 61cm
REAR SHOCK  n/a
FORK    Kona Project Two Aluminum
CRANKARMS   SRAM Via Centro
CHAINRINGS  32/48t
B/B SRAM Powerspline
PEDALS  VP 198
CHAIN   SRAM PC1031
FREEWHEEL   SRAM PG1030 11-36t 10 spd
CHAINGUIDE  n/a
F/D SRAM Via Centro
R/D SRAM Via Centro
SHIFTERS    SRAM Via Centro
BRAKE CALIPERS  Shimano M446 Hydraulic
FRONT BRAKE ROTOR   Shimano 160mm
REAR BRAKE ROTOR    Shimano 160mm
BRAKE LEVERS    Shimano M446 Hydraulic
HEADSET TH ZST No.10
HANDLEBAR   Kona Deluxe Energy
STEM    Kona Commuter
SEATPOST    Kona Double Clamp w/offset
SEAT CLAMP  Kona Clamp
GRIPS   Velo Ergo
SADDLE  Freedom Aon
FRONT HUB   Formula
REAR HUB    Shimano M475
SPOKES  Sandvik Stainless 15g fr / 14g rr
RIMS    Freedom Ryder 21
FRONT TIRE  Continental CityRide 700x32c
REAR TIRE   Continental CityRide 700x32c

About two years ago I converted my 2011 Dew to drop bars. I opted for Avid BB7
Road mechanical disc brakes as they are compatible with short pull road brake levers. For shifters I chose to use bar ends because of their lower price and more simple design compared to STI levers.

I ended up with a cost of about $325 for my 8 speed bar end shifters, Cane Creek short pull road levers, Avid BB7 Disc brakes, Salsa Cowbell 3 handlebars, and bar tape. I would expect to pay that much for the shifters alone if you opt for STI shifters as opposed to bar ends (the economical choice).


Blind rivet nuts for ebike battery on frame: aluminium or steel? I'm planning my first installation of an ebike battery by drilling/riveting the frame (photo of the battery below), here are some details about the project:

The battery weights about 5 kg.
It's a folding bike, and because of the hinge, the battery won't be close to the frame, but shifted up about 15 mm using spacers between the frame (i.e. the rivets) and the battery support. This adds leverage on sideways force.
I wish to put at least 4 rivets. Maybe more, by putting 2 close rivets on some holes of the battery support.
I'm aware steel rivets are much harder to install than aluminium rivets. But I'm planning to buy a good quality clamp, with a lot of leverage.
I'm considering to use M6 fasteners rather than the standard M5 if there is enough room (in
particular for the bolt heads).
Bolts will most certainly be 12.9 steel.

As you may have guessed, I wish the installation to be really sturdy. The bike will be stressed, and I'm really worried about breaking bolts because of sideways force (for example if the bike falls down). So I want peace of mind about this. Also, I encounter many DIY ebikes having battery wobbling issues, and I'd like to avoid that...
So, steel rivets may seem to be a better pick than aluminium rivets, but I think they have a major drawback: if there is an issue with a rivet (e.g. it gets loose and turns on itself), an aluminium rivet would be very easy to remove, just by drilling it, whereas drilling steel would be much, much more difficult. (I know it, on a screwed up steel bolt, I had to drill for many hours, just to remove a very small amount of material...)
Thus I'm hesitating between aluminium and steel rivets, though I'm bending towards aluminium because of the above issue. What are your insights about this?
Update: Here are some details following up to your first answers and comments:

The frame is aluminium. By very rough measurement, the wall thickness should be about 2.75~3mm.
To clarify/emphasize, I'm indeed talking about rivet nuts, aka nivnuts. Not regular rivets.
I'm aware of galvanic corrosion issues, though in the present case it shouldn't be too hard to manage. (and the bikes are stored indoor, that helps a lot)
My previous issue with drilling steel could have been because of inadequate drill bits. I can't say, maybe. It was with a Dremel actually (a pretty powerful one, though).

So, shall I opt for steel rivets?

If ever I had to drill through one, it would be doable by using a good drill bit (like cobalt or carbide), right?
If ever the rivet started rotating on itself, could I just try first to use the clamp again on it?

Update 2:

After some more reading, I have established that aluminium rivnuts would be too weak and inadequate for the job. Therefore I'm going to use steel rivnuts.
People also put some red Loctite (the permanent one), or even JB Weld, when installing; I may go for the Loctite. Using JB Weld sounds overkill, even for me.
I have created a new question, about the spacing I need to put between the frame and the battery: DIY ebike: what system to choose for adding space between frame and battery?. Your insights are welcome!

Personally?  For a heavy battery mounted on raised/cantilevered supports, I'd suggest looking at a welded support and forgo rivets completely.
If you do use rivets, I'd match the metal to the frame to eliminate galvanic corrosion issues.   Four rivets might not be enough - depending on how your mounts touch the frame, you might want "foot-like" lugs, with one either side and at least one in the foreward or aft direction.
Or look at mounting rivnuts in the frame instead, and then use decent bolts into those to hold your battery frame.
Batteries are surprisingly heavy - I once made a 3 point bracket for inside a frame's main triangle.  It used the bottle cage mounts, along with metal straps to the top and seat tubes.  It was barely capable of holding the batteries even with a triangle of stability.


My SPD shoes + cleats won't clip in to my SPD pedals I purchased some touring shoes (Giro Republic) that support a two bolt cleat. I opted for a standard, popular Shimano M520L pedal with matching cleats.

I installed the pedals, loosened the tension on the clip mechanism, and install the cleats with the triangular end facing forward.

Unfortunately, I can't clip in. It appears that the rubber pads surrounding the shoe make contact with the pedal axle before the cleat can engage with the back of the pedal. Note the forward part of the cleat is hooked into the front, as expected. The rear is sitting on top of the sprint mechanism.

My question is, is there something I am doing wrong in my install process? The dealer indicated they have not had reports of incompatibility between this particular shoe and cleat.

Generally the cleats come with some shims for exactly this problem. If you have the box with the original pedals look around for some thin cleat shaped shims.

If you can't find them, you can hand make shims out of plastic milk bottles, or ask around at the dealer to see if they have any spares handy.


How should I train for a hilly ride while living in a flat country? I'm kicking around the idea of riding the Curadmír in the spring of 2015 (almost 600km over 3 days across Northern Ireland), a ride that would obviously have a lot of elevation changes in it (~2000m/day). A year is a lot of time to prepare for it, except for one small problem.

I live in the Netherlands.

A country almost entirely flat and almost entirely below sea level. The biggest hill within 250km of my home is a highway overpass.

Short of getting on a train to the Kapelmuur every other weekend from October to May, how would you recommend I train for riding hills without, you know, riding hills?

Intervals. Lots of intervals. I had a similar problem when training for the Seattle-To-Vancouver ride while living in southern Michigan. We have hills up north and I took a few trips there before the ride, but it really wasn't enough to reduce the suck. This year, I've taken to doing tons of intervals with a regimented training program. In order to keep myself honest, I've been using my bike in a trainer with trainerroad. The measurable progress is rewarding and knowing when I am slacking off is incredibly motivating.


Can i put two rubber rim tapes on a single wheel (single wall rim) I have an old single wall rim type, with spokes protruding. When there is a single rubber rim tape the spokes are forming (coated) "hills" inside the rim which are not sharp but are protruding a bit and i am afraid that they will endanger the inner tube.
Is it ok to install second rubber rim tape over the existing one to flatten out the "hills". The tyres are mtb 12" and the air pressure will be around 60psi-65psi, and the load around 220lbs.
Or is it ok to leave the "hills" forming inside the rim with one rim tape?

Is it ok to install second rubber rim tape over the existing one to flatten out the "hills". The tyres are mtb 12" and the air pressure will be around 60psi-65psi, and the load around 220lbs.

I can see absolutely no harm in any reasonable number of rim tapes. The only downside is cost: you have to pay for two rim tapes. If you start to stack a huge number of rim tapes, let's say over 5, then you'll probably note that the rim tapes cover the rim channel, making tire installation harder than it normally would be.
So try it to see how easy tire installation is. Once the tire has been installed, your only potential problem is tackled.

Or is it ok to leave the "hills" forming inside the rim with one rim tape?

Most likely it's as ok as a single wall rim can ever be. In particular, your wheel is never as strong as it would be with a double wall rim. However, if you really want to use a single wall rim, that's one solution. Note the "hills" don't move much in operation (spoke tension in a rotating wheel is dynamic but the spoke ends shouldn't move because spoke tension changes due to slightly flattening wheel) so they are unlikely to cause a puncture over time. So, it you install an inner tube, if it doesn't puncture in a week of riding it's unlikely to puncture in several years of riding, apart from other external causes of puncture.
To be completely sure, install an inner tube, take it for a ride or two, and deflate the wheel removing the inner tube. Do you see any inner tube damage at the spoke ends?


Simplest and best way to keep water bottles clean and hygienic? Obviously a daily wash with washing up liquid and water is a good start... But with all the use a water bottle gets and the mouthpiece being exposed to the elements whilst cycling through who knows what - are there any other steps you take to ensure your water bottles are clean and hygienic?

And a bonus question - do you use the same bottle forever, or do you replace them after a certain period?

I wash mine in a dishwasher. Mostly because that requires the least effort.

I've had to replace bottles occasionally, I find that eventually the nozzle on the cap starts to leak.


Minimum training maximum outcome My question is: how to get most of minimum training?
The problem is that I have limited time during week and I cannot go out for an 1hour or longer trip and I do not want to ride after dark for safety concerns. However on the weekend I can devote as much as 6 hours in one block.

My goal is to ride 100miles(160km) in about 6 hours without too much trouble. I also want to be prepared for occasional 2-3 day trips with ~80mile days at a slower pace.

My data:

Age:33y, weight: 163lbs(74kg), height:6ft(1.83m)
Current speed: ~60miles(100km) in about 4h05min, breaks included. Last 20miles were rather painful.
Gear: old road bike, no power meter.:)

As for my present training I do random long rides on the weekend, until now they were no longer than 60miles. During the week I do 1 or 2 days of HIIT(Tabata regimen) on stationary bike. I also run about 25miles(40km) a week.

I believe I could do about 3 times 30min on stationary bike at most(boooring).
Should I go with HIIT for 3 or even 4 times per week like in Tabata's original study or should I mix in different types of intervals? But how long could I sustain that kind of training? Have anyone tried that in practice?
I also do not want it to hinder my running too much.

What kind of training would work best for me?

The first thing to say, is that your goal of a 6hr century "without too much trouble" is quite ambitious.  Many cyclists never manage a 6hr century, and even for some quite fit riders, they would really need empty themselves to do it solo.

Training protocols are something of a grey area at the moment, with most coaches still prescribing regimes based on some variation of the books from Friel, Coggan or Carmichael.

However new research over the last few years suggests there may be more efficient approaches.  As you have already found, HIIT shows good results for minimum time investment, although it is still far from clear which combination of work/rest yields the best results.

Polarised training regimes which are based on the intensity distribution of elite athletes have also shown good results, but there is limited information available on how this applies to athletes with less training and recovery time available.

Without a coach to decide for them, the best thing a self coached athlete can do at the moment is read/learn as much as possible, and then decide which approach they feel best fits their goals and restrictions.  Sadly there are as yet a lack of good books available that thoroughly discuss reverse periodisation, HIIT and polarised training.

To me, it sounds like you are already making good use of your available training time, but without making more time available for riding, I think you may struggle to reach your goal.


Cannot reach the bearing adjustment nut on rear wheel I have a Mt. bike with Shimano STX RC components.  I cannot reach the nut and lock nut to adjust the bearing tension.  Any ideas how to make an adjustment so I can reach it?

Also, How do I tell if my rear sprockets need to be replaced.  Can anybody see it it needs to from the picture?

You could adjust the other end instead, so long as the cassette locknut is already tight against the cone (if it isn't, take the cassette off and do that first).

http://sheldonbrown.com/cone-adjustment.html:
"For cassette hubs, or conventional rear hubs that I want to adjust without removing the freewheel, I use a thin 15 mm wrench and the two 17's.

To loosen this type of hub, I usually do have to loosen the left locknut from its cone, loosen the cone, then re-tighten the locknut. To tighten it, the two 17's on the locknuts do the job quickly and easily."


Speed and Cadence Bike Sensor Opinions I'm looking to start tracking my speed and cadence for my iOS app, Cycle Meter.  The app works great for distance, time, but is not accurate at all for measuring my speed.

So I'm thinking of buying a Garmin or a Wahoo speed/cadance sensor and wanted to get the community's opinion on the two.  I'm not worried about price.  More about quality, functionality.

The two in question are:

http://www.wahoofitness.com/Products/Wahoo-Fitness-Premium-Speed-and-Cadence-Bike-Sensor.asp

https://buy.garmin.com/shop/shop.do?pID=1266

Update:  been using the Wahoo one for a few weeks now and have to say that I'm very happy with it.  I've been in a lot of rain as well with no issues.

Fady listening to music while riding is probably the most dangerous thing you can do so do not explore that idea please.. With that said I use the edge 500 and it has loads of functionality and will most likely support all your needs. You will usually need to purchase a speed/ cadence sensor with it. Battery life is great so long as you have it set to turn off with inactivity. I do still carry my phone in my jersey pocket when out alone just in case somethin happens.


Best rear derailleur for a Schwinn ranger? A few days ago the cog on my Schwinn Ranger rear bike derailleur broke in half after changing gears.

I examined the cog and it was made of flimsy plastic. Was wondering if I could put a new/different rear derailleur on there for this same make and model but of higher quality, with metal cogs.

The bike derailleur that was on there before was a Shimano tourney tx which go for about $6 online. Want to upgrade but not sure how to go about it or what is the correct ratios and such for it.

I know with car parts everything has to be in accordance with the brand and specs. What rear bike derailleurs would be the best fit for a Schwinn Ranger? 21-speed.

Any Shimano rear derailleur designed for 7 speed (3 front x 7 rear gears =  21 speed) drivetrains and mountain bike gearing will work.

For your practical purposes, the compatibility chart from Shimano below gives part numbers for the available rear derailleurs which will work with a 7 speed MTB drivetrain:

Those part numbers can be specifically matched for each derailleur.

To break down the part number I will use RD-M360 as an example.

"RD" = Rear Derailleur - "M" = Mountain Bike - "360" = model ID number
"RD" = Rear Derailleur - "TX" = Touring Bike - "800" = model ID number

Typically, the higher the model ID number, the better quality the part.


Has Shimano produced Ultegra 600 Hub Set, 32 hole? I found this item at an online shop, but can not find infomation about this product. Anyone knows this hub set? and any review infomation available there?

I'm no expert on Shimano components, but according to Sheldon Brown and Velobase, there were many 32H hubs from the Shimano 600 series: "Shimano added the word 'Ultegra' to their 600 group set in 1988 with the introduction of the 6400 series groupset. Also often recognized by the tri-color stripe on many of the parts."

According to Velobase, this is a 32H Shimano 600 Ultegra hub. I'm not sure if that is what you are looking for. Here is another.


Play in headset with no upper bearings on a tandem bicycle I have a half recumbent tandem bicycle. The front fork headset (under the front cyclist) is loose: I can feel some play when I put the front brake on and try to move the bicycle front and back. I tried to tighten it with no success. I disassembled it and was surprised there was no upper bearings. Could this be normal, given the bicycle geometry (not much clearance between the front seat and the headset and no need for a stem) ? I found some kind of seal which was torn out. Could this explain the loose headset ? Any help would be appreciated.

NB: the bike frame is from Bilenky (viewpoint) but the set up was done by another company.

A single bearing race really isn't very good at resisting torque perpendicular to its axis, so I'd be surprised if there wasn't meant to be a set of bearings in the top. Even closely spaced sets of bearings aren't great in that regard. Unless there's a special arrangement inserted from below, the lack of a top bearing would be likely to cause play, and possibly damage. The lower bearing should be checked in any case. The load on a tandem is quite high so I'd expect a robust design using the full available steerer tube length.


Help me identify these retro hubs I'm looking to get some NOS hubs to use with a screw-on singlespeed freewheel, the ones I'm using right now are far from perfect and I will not be able to rebuild them (the hub body itself is worn on the rear).
The seller says these are Ursus brand. Were these any good?

Ursus is a real brand, even though you don't see a lot of them in the US. Most of their current stuff is fairly high-end, but the ones you're showing look pretty basic (and fairly old- by the 90's hubs were mostly cassettes, not freewheels). Should be fine for road riding/ commuting as long as you know how to lace a wheel. Otherwise the cost isn't going to be worth it and you should just get a pre-built wheel or wheelset.


Is it possible to install a thru axle on a bike, which is a few mm to shorter than the bike frame's thread? I installed a thule thru axle on my frame, but it is a bit shorter than the original one (newman, see pic).
I think 4-5mm to short.
Furthermore, the original one is CONIC, and the replacing thule one is 'flat'.
Can this hurt my frame?

You can never replace a conical interface thru axle with a flat shouldered one. That's just the wrong part.
Lack of contact area may cause the axle to loosen or the frame to become damaged. But what will probably be a more immediate problem is that most frames with a conical interface have a hole for the axle shaft that's a pretty loose fit, and often gappy by a millimeter or more. The reason is they're using the conical interface to locate the axle and prevent it from squirming under load, which is actually a much better design than relying on the tolerances of a plain hole, and probably the only reason it's not universal is because of cost. Don't sabotage your bike by plugging in the wrong thing.
Some aftermarket thru axles are sold with a conical washer and two lengths are given. One is for with the washer, one without. It's a way of halving SKUs needed.
As for your original question of missing thread engagement, it depends more on what engagement length remains, not what's missing. That said, wheel retention is probably the literal worst thing on a bike to play thread engagement safety guessing games with. I doubt anyone who knows what they're talking about would be comfortable stating a generic minimum safe thread engagement number, other than 100%. In practice I've been allowing no more than about 0.5mm of missed engagement and have mostly been erring long.


Removing old fashioned saddle from seatpost I've been searching for instructions on how to remove my old saddle from my seatpost. All the videos/guides I've seen have been about the newer kind of clamping mechanism where just one bolt needs to be loosened with an allen wrench. Mine is different- there are two bolts on either side of the saddle and none of my tools seem to fit. (It's an HL Aluminum Micro Adjust 27.2 X 300mm). How can I remove it??

I found that the GMC Denali 21 speed uses an HL Aluminum Micro Adjust 27.2 X 300mm, so I assume your seat is very similar to those found on the Denali. In this case you will need a small crescent wrench that will fit between the guts and the side of the saddle. Some bolts are square and will stay put when loosing the nuts, but some are not and might require an opposing wrench on the other side. You only need to loosen each side a half turn and you can slide the seat off the post. The problem is that you will only be able to replace it with similar guts. You might be able to swap out the saddle itself if the rails match, but my recommendation would be to switch the whole saddle/post with a more modern set.


What replaces Shimano Deore LX rear derailleur RD-M570? They stopped making my current derailleur in 2003. I need to replace it. How do I choose a replacement part?

A good answer will tell me a specific part (with part number) that will replace the RD-M570. A better answer will also teach me how I can look up this information for myself.

Thanks

Ignoring number of speed for a moment, derailleur rear specs are:

Total capacity
Max front ring difference
Max/min largest sprocket size
Min/max smallest sprocket size

All measured in numbers of teeth.

Total capacity is (diff in cassette smallest-largest sprocket teeth) + (diff in chainring smallest-largest sprocket teeth), it's basically a measure of how much chain slack a derailleur can take up. A longer cage means bigger total capacity, but also less chain tension and control.

Shimano very kindly publishes all their specifications here. Note there is a link to archive PDF docs on that page which go back to 2004 so you can look up the RD-M570. Looks like it only came in an SGS (long) cage version.

Total cap: 43
Max front diff: 22
Large sprocket max: 34
Small sprocket min: 11

Putatively you need a Shimano 9 speed MTB derailleur, but in fact you could use an 8 or 9 speed derailleur that has the required capacity. The reason for this is that 8, 9 and 10 speed cassettes are all the same width and Shimano used the same derailleur actuation ratio for 7, 8 and 9 speed MTB systems (the ratio of length cable pulled to derailleur cage movement).

If you want a new derailleur, you pretty much want to go for the highest spec 8 speed available, which at the moment is Alivio RD-M4000.

Total cap: 45
Max front diff: 22
Large sprocket: 36-32
Small sprocket: 11-12

That will actually enable you to run a slightly bigger cassette.

You could get an older but higher level model on Amazon or Ebay, say if you wanted to get something that has the same look at the rest of groupset components on the  bike. The Shimano Wikipedia page has a nice summary table of Shimano MTB groupsets where you can look up what groupsets were 8 or 9 speeds.


how do you remove rear wheel on scott genius 920? It does not have quick release. You obviously unwind a lever on one side which unscrews the gear side from frame ... but once this is done there is no obvious way to me how to progress. All Scotts manuals ignore the issue making me think it is really simple (and I'm really stupid!) or has to go to the shop!!! unlikely

I couldn't find any images just a description. Apparently it is similar to a conventional skewer. The difference is, the skewer is removed to drop the wheel out of the frame. The nut that typically is not removed is captured in the frame. Some owners have complained it is difficult to line up the skewer with the "nut"


Cycling on the sidewalk/pavement fines in belgium/netherlands So, when cycling there is one narrow, but busy road I always 'evade' parked cars by cycling a bit on the sidewalk. I am aware this is entirely illegal, however compared to the alternative (stopping every 30 seconds for the 5 minutes it takes me to get to the end or jumping in front of cars which by law should break and drive behind me... but they are going a bit too fast for that) it is a risk I am always taking. I do wonder however, how badly would I be fined for this if caught?

PS. The road in question is in Belgium, so for all practical purposes I only care about the Belgium fine, but as I am Dutch I tend to do this to a lesser extend (the Dutch traffic situation is far better) in the Netherlands as well so would love to know both fines.

Fines in the Netherlands for the two most instances of wrong "place on the road" most likely to apply, are at the moment € 55,- although there's always article 5, which says you shouldn't endanger others on the road.

I couldn't find any definitive data on Belgium.


Presta vs schrader valves Are there any advantages of presta inner tube valves over schrader inner tube valves (or vice versa)?

Presta

schrader

I've always wondered why 2 exist. Apart from their radically different design I don't understand why you'd choose one over the other.

Depending on your rim (bore diameter) you don't have the choice unless you are willing to tweak your bike a bit (or use an adapter). Cross-Country or Marathon Hardtails and racing bicycles usually use Presta aka Sclaverand or French Valve (at least we call it like that in Germany). This type of valve opens when you put the pump on it (after you opened the screw). This allows for measuring the pressure but unfortunately it can be really annoying because you normally release some air when trying to set the pump correctly. Still, Presta allows for a pressure up to 15bar. This is required by racing bicycles. A disadvantage is the thin and long shaft which makes it more likely to bend the valve unwanted. Still this can be an advantage because this more elegant design reduces weight and therefore dynamic unbalance.

Schrader only allows up to 10bar pressure. Because the valve opens mechanically, we can measure the air pressure just like for Presta. The risk of loosing air/pressure at the beginning is lower because you first set the pump on the valve and just afterwards open the valve with a lever.

The biggest advantage of Schrader is that you can use pumps at gas stations without an adapter. Those adapters are really cheap and small, I always carry one in my purse between the change. But still you don't have the risk to loose that adapter when you are using Schrader valves.

The biggest disadvantage of Schrader is the relatively small pressure you are able to establish using hand pumps due to the bigger cross sectional area (p=F/A). Because of the differences in the mechanical construction and therefore the sealing, also with automatic pumps you can't achieve the big pressures compared to tires with Presta valves.

As you can see both valves have their pros and cons. Simplified, If you have

thin rims and/or
don't want to disturb the stability of the rim and the dynamics of the tire and/or
need big tire pressure and
don't care about the issues of maintenance

you should use Presta. For all other cases, use Schrader.

By the way there are more than two types of valves used for bicycles but I think the two mentioned are widest spread


Cheap clothes for 50 km per day in the summer I am considering of paying DeaxExtreme's clothes, because they are rather cheap and seem to be rather good in the summer.

I would like to have a cloth that keeps me warm as it rains and as I cycle 50 km/h maximum. I am therefore considering of having a fleece and ECWCS level 1 layer under the given cloth, just in case when it gets cold. I should definately keep a scarf to protect my throat with the given cloth.

Are DX's clothes worth the money?

I am wearing at the moment polo trousers with elastic boxers and a jacket with fleece underwear which does traps water inside. Continuous chafing and the wet jacket are my main problems.

The temperature range is often -10 - +36 C from the morning to the day temperature in the summer. The weather is often windy. I am living in many countries such as Sweden, Norway, Finland, Germany and France.

Is there any clothning that breathes and blocks wind well?

You've got some pretty demanding criteria there, especially if you have such wide variations in a single day.

The key is "layers" -- different pieces of clothes you can easily put on or take off as conditions change.  And, for that many layers you'd probably want to have a pannier or some other sort of bike bag to carry what you're not wearing (though you could probably get by with a backpack).

Since cost is a factor, you should start with what you already have (maybe not designed for cycling) and add a few critical pieces.

First and foremost, you need some good rain clothes -- a lightweight jacket that is waterproof (or close to it) and some sort of pants that shed water well.  The jacket needs to "breathe", so you don't begin to sweat too quickly.  (But even if it "breathes", you'll find that it gets sweaty very rapidly.)

You also need "wind clothes", so the wind doesn't penetrate your clothing on a cold day.  These should be anything that is thin but tightly woven (but not waterproof).

Otherwise, you need layers of clothes that keep you warm without making you sweat and without holding sweat (or rain) close to your skin.  Wool is the old traditional favorite here, though there are many synthetic fabrics (such as CoolMax) that are better (and not as scratchy).  But stay away from synthetics such as nylon, polyester, etc, except perhaps as a thin outer layer.

Cotton is to be avoided in cold weather (because it insulates poorly and holds moisture against the skin), though many of us prefer to cycle in a simple cotton tee shirt in warmer weather.

All of these clothes should fit fairly tightly, so they don't flap very much in the wind.  (Though the rain jacket should maybe be a little looser than the others, both to "breathe" a little better and because you frequently need to put it on and take it off in a hurry.) Flapping slows you down and also reduces the insulating effectiveness of the clothes.


Are Shimano R7000 chainrings (50 and 34T) compatible with Ultegra R8000 crank? I need new chainrings due to slipping chain and decided to replace them. I currently have an Ultegra R8000 Chainset and don't want to replace the crank arms (as it is really expensive). Ultegra is almost 50% more expensive for the rings. Will the Shimano 105 R7000 chainrings fit this crank as I have heard different opinions on this and wanted to get some certainty from someone?
Many thanks

Yes, they are 100% compatible. See https://si.shimano.com/api/publish/storage/pdf/en/ev/FC-R7000/EV-FC-R7000-4331A.pdf https://www.bike24.com/p2284436.html
R7000 & R8000 chainrings are a 'B' match, that is different materials but compatible.
With a 50/34 compact, then the rings are 'MS' pattern. Previous generation are 'MA', which is incompatible.
There is a high chance you can use the even cheaper/heavier RS510 chainrings, which are also 'MS', however I haven't seen that confirmed.


Social network for bike users Does a social network exists for bicycle users?

I'm working on a website that caters bikers who want to discover some parts of France, and I'd like to allow bikers to share their experience. I could use FB, but some other soc net are maybe more relevant.

What would a biker do?

Warmshowers is certainly not a "social" network in the meaning of socializing only on the internet. But it is an internet-organized network for socializing with other cyclists in the real world. Certainly a good fit to this question's tags touring and social. It's a great opportunity to meet really nice and interesting people - highly recommended!


What can be done to make a trainer work quieter? I use a trainer at home. It works quiet. But living in an apartment I would like to make it work quieter. What can I do to minimize noise of a trainer?

Baffling - place it on carpet or a rug (and several towels), this will both stop vibration through the floor and catch the drips of sweat.


On which weather conditions should I choose my bicycle with studded/spike tyres? I've recently bought a new bicycle for my daily commuting and fitted my old bicycle with studded/spike tires as a dedicated winter commuting bicycle. (They're Schwalbe "Winter" tyres, not "MarathonWinter" as I initially wrote on Twitter. I'd have bought MarathonWinter, but they're not available in 16".)

Now I wonder when I should choose which bicycle (both are Bromptons), especially under which weather conditions?

I've seen and read When are studded tires necessary?, but on the one hand the question's focus is a little different and on the other hand, none of the answers really answers my question.

A little background:

Two years ago I had a self-caused bicycle accident on a dry and sunny winter day due to snow melting, flowing over the street and there freezing immediately again.
I've thought about using studded/spike tyres for quite a while and after that accident I'm sure that there are cases where they would help.
I live in a hilly city (Zurich) and there are a few weeks per year with snow and icey conditions, usually in January and February.
I have been convinced that riding with studded/spike tyres all winter long is a bad idea if most winter days are probably fine for normal tyres, so I've come to the two-bicycles solution to be able to decide on the right tyres without any time penalty for switching wheels.
Since my commuting bicycle is a Brompton with six gears and dynamo hub, switching wheels in the morning depending on the weather isn't an option anyways.
When I fetched my winter Brompton from the mechanic and did a test drive with the studded/spike tyres, I noticed that they're really loud and that indeed will only ride that bicycle when necessary.
I don't care about rolling resistance or possible speed. My daily commute is a inner-city ride of about 5km.

So far the winter was really dry and there was no need for studded/spike tyres.

But when should I switch to my winter bicycle with studs/spikes? My current idea is the following:

When there's snow or snow mud on the streets. (Deep snow is seldom and usually gets cleaned up rather fast, but there's often still a thin layer of slippery snow mud on the streets, especially if the city runs out of gritting/thawing salt.)
When the previous days were rainy and the weather forecast talks about freezing temperatures. (→ chance of water freezing over)
When a sunny day follows cold and snow days to avoid the case where I had my accident two years ago.  (→ chance of water freezing over)

Are there any other conditions on which I should use studded/spike tyres? Or am I overcautious due already having had an accident on unexpected ice? E.g. many years ago I easily survived this kind of weather with normal Schwalbe MarathonPlus tyres.

I've got the same tyres in 700C, but only run one bike (in this city). I put them on a couple of weeks ago and they'll come off when the weather warms up in spring. There's no harm in using them all winter. In fact on a thick layer of wet leaves they're better than my marathon plus. They are noisy, but you get used to it and it doesn't down out the traffic.

One of the worst times round here for sheet ice is frosty Monday mornings, which often follow a sunny Sunday afternoon when people wash their cars. The residential road that doesn't drain very well is one of the few that isn't gritted on my route.

You're in a slightly different position to me of course. I suggest a simple rule: if it was forecast to be below about 3C at any point overnight, use winter tyres. If there's visible frost on the ground, use winter tyres. If you're planning on coming back late and the forecast is for less than about 3C, use winter tyres.


Size of mountain bike I am 180 cm tall and I recently bought a Talon 3, with large frame and tire 29 through the website. I searched and I found that large frame is good for me. When I wanted to pick it up, I found it seems large for me and when I seat, my toes just touch the ground. Can I know if it is ok and I should replace it with another bike? I am new and I am not familiar how large my bike should be and what tire size is perfect.
Thanks

as the comments have said. It is good to have your legs able to fully extend when your pedal is at its lowest point. It makes for easier pedaling, I am about your size and I also have a 29in mountain bike. The bike is worth keeping, an easier way to get on would be to step over the frame and as you start pedaling slide onto the seat.


What's the longer-valve, metal-ring inner tube style called? I have an innertube for a Chariot stroller that apparently came from Europe, and the local bike shop people couldn't find one in their catalogs that was both the right size and having the thing I'm trying to describe.  I want to search for it myself but don't know what it's called.  It's a longer than normal valve, and has a washer-like thing (metal, but thicker than a washer, and threaded) that you spin down the valve until it locks the valve in place to the rim.  (We need one because we're going through innertubes like crazy--whenever you pump up a Chariot with the compact style pump we have, it wears the crap out of the valve.)  They could find it in the skinny Presta valve diameter but not in the standard valve diameter.

What's it called?  (And if you happen to know, where in Canada can I order one?)

Thanks,
Kev

You can see some images of alternative valves at the Schwalbe page.
Your local bike shop is certainly familiar with Schraeder (aka "Auto") and Presta (aka Sclaverand) valves.  It's difficult to tell from your description, but it's therefore likely either a Regina or a Dunlop valve.


Is it worth it to get a bike computer with cadence? I'm looking into purchasing a bike computer, primarily to track distance and speed. Is it worth it to go up a notch and get a computer that also tracks cadence? How accurate are bike computers at doing this? I'm not interested in wireless computers - I hear too much about interference, and they are much more expensive (thus targets for thieves) -- so is it worth it to hook up more cables to the bike in order to get cadence info?

I also think the answer is "it depends", but for slightly different reasons to Daniel. I think it depends on why you're cycling.

If you are training, then measuring cadence can definitely be useful. In fact, there are training programmes that are based around cadence. (You're basically looking for a high value, and a steady value.)

Otherwise, the information has more-or-less interest value only, although you could still argue that the "steady" side of the value could be used just to improve your technique.

As regards accuracy, cadence is measured using a magnet, just like speed and distance. So there's no reason why cadence should be any less accurate than speed and distance. It depends on the hardware of course but I'd expect computers these days to be pretty accurate.

As regards your reservations regarding wireless technology, again its going to depend on hardware but wireless is the way all the high-end computers have gone, so there is certainly not any inherent problem with this technology. It is possible to measure things like speed, cadence, power and heart rate, even I believe gearing info, all simultaneously, all wirelessly and without interference.


What is the convention for highlight colors on cue sheets? I've noticed on group rides that some cyclists highlight turns and other information on cue sheets in different colors. Is there a universal convention for the colors used? (e.g. blue for left turns, pink for right)

There's no convention for it, it's entirely down to personal preference.


Is it common for the left side spokes of a front disc wheel to have more tension than the right side spokes? Wiping my bike down after a wet ride, I noticed that the left side spokes on my front wheel are tighter than the right side.  I don't have a tensionometer but squeezing pairs on each side and plucking spokes around the wheel yields a feeling of increased tension and a tad higher pitch sound of the left side spokes. This is generally so around the entire wheel.

The wheel is a 26 inch Mavic 119. The 32 spokes are laced 3 cross.  The 9mm QR axle is fully engaged in the suspension fork's dropouts, and each side of the rim is equidistant to the inside of the fork leg. With the tire still on, can see it seems to run true and centered. The disc rotor is 160 mm Shimano.

Do disc-brake wheels have greater spoke tension on the left, rotor side?

The side with the disc is dished in more than the other (that is, the spoke flange is closer to the hub's centerline), so yes, I would expect it to have higher tension.


How can I unbend, straighten or flatten a bent rotor? Some possibilities, which I haven't tried:

try to bend it back into shape with my hands while still mounted
take off the rotor, sandwich it between a couple of wooden blocks, put some weight on it and leave it for a night

Try a Park DT-2 rotor tool or something similar.I've used a large adjustable wrench with mixed results.Usually the larger the clearance between the pads and rotor the more forgiveing it will be to the rotor being a little off.I leave the wheel mounted,spin it to find the high spot .Then tighten the wrench on to the rotor and flex gently to straighten the rotor.


What kind of paint should I use on my plastic mudguards? I tried repainting my plastic mudguards (fenders) using automotive spray paint. It went on easily and covered well with two coats, but it has no abrasion resistance at all. Within a few weeks my paint job was full of holes where I'd parked the bike leaning on something, and where I'd D-locked the front wheel.

Is there a kind of paint more suited to this task?

My first step would be to scuff the surface with a Scotch Brite pad. You want some minor surface imperfections for the paint to adhere to. Clean the surface with either alcohol or what the instructions for the particular paint call for. I am partial to automotive brake cleaner. If you can get it, use Rustoleum Spray specifically for plastic. Apply two coats of primer. Allow it to dry between coats. Then apply two color coats. You have to use a paint intended for plastic because conventional paint will not flex without cracking or chipping . As @Daniel R Hicks has stated, allow the paint to fully cure before it experiences any contacts. If you can set it in the sun for a couple of days it should excelerate the hardening. Even doing this the paint may chip if the fender experiences severe flexing.


How to correctly adjust 3 speed shifter I have a second hand chapelli 3 speed bike.

Everything was fine until I got a flat tire on my back wheel.

I was able to figure out how to get the back wheel off (after a bit of Googling), by disconnecting the back shifter and thus allowing the wheel to come off.

After putting the tire back on, I realised I had moved the lock nut for the adjuster and couldn't remember quite where the shifter adjuster was previously set to. I put it back to where I thought it went and took it for a test ride and it was fine.

Recently, I have noticed that sometimes the gear slips a little (I think that's the right word for it) when I am riding and I change gear; I will be pedaling and it feels like it "slips" as the pedals will drop a little as if missing something and then pick back up normally.

I found a manual for my shifter online today, and the diagram has suggested the below is where I should adjust my shifter to:

I'm not a huge bike person and less so a mechanic and so had a little trouble following the instructions for "Gear Adjustment" on the manual I linked above. Based on the diagram, I got my shifter adjusted to the below:

Have I interpreted these instructions correctly?

I actually use that hub quite a bit, and was just looking into that setting for one of my customers earlier.  The "set" gear is 2.  set the shifter in 2, then yes, you want the connection from the chain to pin to be just protruding from the axle.  Once you set it like that once, lift the back wheel off the ground and pedal it one revolution forward and pedal it backwards to engage the brake once just to be sure it's engaged in the gear, and check it again.  If it has "settled into gear" and the position of that pin has changed, set it again.

Once you get it so in gear 2 the pin has stayed at that point, you should be good.  Check that all gears are working, and that it isn't slipping like you said in your original post.  Riding it for long periods of time with it slipping out of gear will wear out the internals very quickly.


9 speed SRAM shifter for dropbars? Does anyone know if SRAM makes a 9 speed compatible shifter for dropbars? What's the best option for shifter/derailleurs for a 2x9 cross bike?

SRAM's current lowest-level groupset is Apex, which is a ten-speed setup and Rider_X says that SRAM have never made a nine-speed road groupset. Campagnolo also only seem to offer ten- and eleven-speed, so Shimano Sora is the only nine-speed in the current line-ups of the big three.


How accurate are indoor trainer power meters? I recently got a Tacx Flow trainer, this being the first time using a power meter. For about 10 years, however, I have been doing monthly "uphill time trials," whereby I put the time into that formula which, supposedly, determines your power. (Mass X height of climb, divided by time (seconds) = Newton meters X 10 = watts.) For that, I've been averaging about 300 - 330 watts for around 13 - 14 minutes. Yet, on the Tacx, I've done just an 8 minute effort (for determining CTS training zones), and can only manage 250 watts. I realize neither of these is going to be as accurate as a PowerTap or SRM, but that seems to be an awfully large discrepancy, especially considering how its the shorter effort is so much lower. I know fatigue starts setting in, but on the Tacx, it seems like the resistance is gradually increasing, or some thing. Or, is it possible something isn't set up right? (Yes, I did put my body weight in.)

I will presume you are asking about the types of trainers that one mounts one's own bike onto, and not a dedicated "bike" trainer such as a Monark ergometer or a CycleOps Indoor Cycle (ergometers such as these are used in exercise physiology laboratories and can be calibrated to be very accurate).

Consistency and Accuracy of Speed Measurement

Accurate power measurement in most indoor trainers depends on accuracy in speed measurement. A full description of the relevant factors is long and complex. The short answer is that some indoor trainers are more consistent and accurate than others, and we can group them into rough categories.

In general, accurate power measurement from an indoor trainer depends on a consistent load response with respect to speed. Thus, your question is equivalent to asking, "how consistent is recorded speed for a given power input?" If that relationship is consistent then you can simply put a speedometer on a trainer and convert the observed speed to power. A handful of modern software applications (e.g., Trainerroad or Golden Cheetah) do essentially this: one mounts an ANT+ speed sensor on the bike and, if the trainer is consistent in its response, the application converts that speed into power.

The speed-power relationship will depend on tire pressure, the tire-to-roller contact pressure, the ambient temperature, and the type of resistance unit used by the trainer to generate the load. For example, common types of load generators include wind fans, magnetic resistance units, fluid resistance units, and electric load generators; rollers use frictional resistance generated by tire deformation, belt losses, and (a very small amount of) aerodynamic drag generated by the spinning rear and front wheels. Wind-turbine fans tend to be quite consistent as long as the tire-to-roller contact patch is consistent and air density is constant. The relatively new Lemond Revolution Trainer uses a large fan directly driven via its own cassette so does not rely on a tire-to-roller interface and independent tests have shown that its speed-power response can be both precise and accurate. Some discussion of how the tests were performed and the drag parameters were estimated are here. As an aside, wind turbine trainers tend to be quite noisy.

Because the load generation on a set of rollers is mostly determined by rolling resistance it, too, can be quite consistent. Measurements with a calibrated Power Tap show that if tires, tubes, air pressure, number of wheel spokes, and total mass are known, rollers are extremely consistent: consistent enough that high precision estimates of rolling resistance can be made using this setup. For example, the differences in the rolling resistance of tires and tubes described at biketechreview.com were measured using rollers and a calibrated power meter.

The consistency of magnetic and fluid load generators tends to degrade with temperature. Some fluid generators use more temperature-stable fluids, and thus tend to be more consistent than magnetic load generators -- however, one fairly well-known brand of fluid generator trainers has a distinct "temperature threshold" through which it passes so the resistance is quite step-like. The consistency of both magnetic and fluid trainers can be improved if one can maintain their load units at a steady equilibrium temperature.

Among the trainers with electrically-based load generators, the Computrainer, the Velodyne, and the Velotron are reportedly consistent and can be calibrated to be accurate against a known accurate power meter.

The Tacx Flow

In my experience, the Flow is not particularly accurate although in certain modes it can be consistently inaccurate. In other modes it is inconsistently inaccurate. However, in all test modes I've used, the Flow overestimates rather than underestimates power compared to a Power Tap.

To demonstrate consistency of the Tacx Flow, I collected the data below with the same tires, same tubes, same bike, and same rolldown calibration number (of zero). The black and red dots were collected four months apart in time, for four different "slope factors" and demonstrate that over that period the speed-reported power of the Flow was consistent.

However, while consistent, the Flow was inaccurate. There was no combination of calibration number, scale factor, and slope that I could find that would produce accurate power estimates across the range of speeds tested (accurate compared to a known-accurate Power Tap). Since I had the Power Tap, I quickly gave up trying to find the "right" parameters. However, over a "moderate" range between 200 and 300 watts, a scale factor of 85 and a rolldown calibration number of 4 came close -- above and below that range, the Flow grew worse.

That was for the Flow in "trainer" or "slope" mode. In "ergo" mode, where the Flow is supposed to adjust the load in order to keep power constant even if the rider changes speed and cadence, its performance was abysmal. In the plot below, three different scale factors were tested for a set ergo power level and varying wheel speed. If the Flow had been able to adjust the load to keep power constant at varying speed, power (as measured by an accurate Power Tap) would be independent of speed and each group of dots would be horizontal. As can be seen, they are not. This demonstrates that in ergo mode, the Flow's load generator is easily overmatched at high and low wheel speed. It is thus wise not to rely on the Flow's ergo mode.


Cube stereo 150 race "do not clamp" warning I have the following warning on my (carbon) CUBE stereo 150 race (2019) :

  Ultra thinwall tubeset
  DO NOT CLAMP

Currently I clamp my bike like this, and make sure that there is nearly no force applied. The rubber on the clamp keeps it from sliding away:

Does thinwall tubeset means that the entire frame of my bike should not be clamped or only where my dropper post is? If so, how am I supposed to perform maintenance on it?

ps: there seems to be no manual for CUBE 2019 bikes.

I believe that you should not clamp anywhere on a carbon-tubed bicycle. As @whatsisname discussed in this Stack Exchange post, carbon fiber can be made very strong, but if you want it to resist clamping forces, you have to specifically design it to do so. That would add weight. All our fancy carbon frames are designed to be strong in some directions only, and they are not designed to withstand clamping forces. For that matter, the tubing on aluminum frames is very thin, and I believe the general recommendation is not to clamp aluminum frame tubes either. One best practice would be get a cheap alloy seatpost and clamp that. Some discussion here from a Trek dealer in Chicago. They point out that clamps really concentrate the clamping force in a few places on the tube. So, you could be exerting more clamping force on the frame than you perceive.

Park Tools has a pro mechanic stand that clamps bikes through the front axle. If you go to the page for their home mechanic stand, the picture clearly shows them clamping a bike by its seatpost. They also suggest that you can clamp a dropper post with some precautions. The link goes to a YouTube video, and their synopsis of the issue starts at 11:00. The link should play from that time, but you can replay that video from the start if you are interested in an engineering discussion of clamping forces on seatposts.

If you search the internet, I think you'll find some people who say they've clamped their carbon frames gently without issue. They may well be right! However, the issue is that they may have caused invisible damage inside the carbon. Raoul Luescher, who repairs carbon bikes for a living, discusses that issue in this YouTube video. His discussion is not specific to clamping, but he makes the point that you can cause delamination (fancy term for a fracture) in a carbon bike from something as simple as letting it fall over at a coffee stop. Importantly, you can have a delamination that's not visible from the outside of the tube. It's possible that the delamination will propagate (i.e. get worse) over time, and then fail unexpectedly. He specifically said in the video that he gets a number of failures while "just riding along". His point is that well-made carbon fiber won't fail like this; there has to be a flaw (e.g. manufacturing process left voids, which propagated over time) or invisible damage.

Please note: this does not mean you have killed your fancy carbon frame. It merely means that clamping your frame, even lightly, is not safe in the long run.

Side note: An extremely expensive but flexible adapter solution for your stand is Silca's Hirobel, further discussed here. This supports a frame from below the top tube using rubber wheels, and it places rubber straps around the top tube. This is probably not worth it for most people. I am including this link for fun. And who knows, you might decide it's worth it in terms of hassle saved.


Proper Posture on a flat bar road bike I've been commuting on a flat bar road bike for a couple of years now. The ride feels comfortable but whenever I see myself riding I always think my posture is wonky.

Is there a guide somewhere or picture that shows proper riding posture on a flat bar road bike? I've seen many of racers but none of flat bar/hybrids.

I've attached the image of my bicycle, will try to get a picture of my posture on it soon.

If it's not broken, don't fix it. The act of folding ourselves onto a bicycle, (especially one with any kind of aerodynamic advantage over a mountain bike) is not a natural-looking position for a human body. We're built to be more or less upright, which is not an aerodynamic position on the bike.

So, if you're comfortable on your bike and feel like you're ok with the amount of wind-resistance you create for yourself, and your bike is properly sized for you, there's not much you'd really want to change.

A couple of general bike position loose guidelines (yes, general and loose are a bit redundant here, but these are not hard fast rules):

If you look down at your front hub while riding, you want it to be somewhere in the vicinity of being hidden by your handlebar.
For a commuter bike, you want to be able to look forward (with your head more or less erect) without feeling like you're craning your neck.
In said upright-head position, you shouldn't have to stretch for your handlebar.
Your seat should be at a height such that your leg is mostly extended at the bottom of the pedal stroke, but you should not have to rock your hips at all during the bottom of the pedal stroke.
Your seat should be situated fore/aft such that you can do the following:
a. Tie a weight on the end of a string.
b. Hold the non-weighted end of the string in the slight hollow on the outside front of
 your knee.
c. The string should fall close to the spindle of your pedal when that pedal is at the
 front of the stroke (3 or 9 o'clock, depending on how you look at it)

If all these things hold more or less true, and you're comfortable when you ride, don't stress what you look like.


Replacing rear hub, beginners advice required I have a Trek 1.5 2011 compact road bike that I abused a bit too much over winter.

The rear hub has quite a lot of sideways play on it and I am buying the tools needed to hopefully fix this. My concern is that even if I manage to remove the play on the hub the bearings will still be ruined (fairly likely).

What I'd like to avoid is having to remove any spokes.. the idea of building a new wheel scares me quite a bit! Or perhaps I'm being afraid for no reason?

What I'd like to know is what my options are if I find the bearings have had it. I don't really know what I'm talking about but in an ideal world I'd just replace the hub with a drop in replacement. Does that exist? :) I don't mind getting my hands dirty, but at the same time I want to ensure I have a bike to ride!

There's two general types of wheel bearings: cup and cone and sealed cartridge bearings.

Cup and code bearings were very common years ago and are even still used on some high end Shimano hubs (dura-ace). http://sheldonbrown.com/cone-adjustment.html. These bearings are easily replaceable with minimal tools. If you have these bearings and have worn them down too much, they can damage the bearing race in the hub. In that case you'd need to replace your hub.

Cartridge bearings are more common today. (http://www.pinkbike.com/news/To-the-Point-Cartridge-Bearings-2013.html). The advantage of a cartridge bearing is that even if it wears badly, it's not going to damage the hub. The disadvantage is that they are pressed into the hub shell and require more (and expensive) tools to service.

I'd be surprised if your bike had cup and cone bearings, but the only way to know is to do a little investigation. If the races aren't worn, replacement is quite easy. If you have cartridge bearings, any bike shop can easily press out the old ones and press in the new ones.


Loose thread (stripped) tapered bottom bracket frame connection The threads in the MTB frame that is supposed to hold the bottom bracket lock rings were very loose and it can't hold the bottom bracket in place. The previous bike owner tried to apply Teflon tape in it but the lock rings still moves out of the frame if pushed from the other side.

Any recommendations on what to do?

Add more Teflon tape?
Convert to a hollowtech crank?

A video could really help, sounds like the threads of the cups and/or of the frame shell are damaged. Probably the Bottom Bracket cups need to be removed so the threads can be inspected for damage, like rust, or cross-threading, stripped threads etc. If the threads of the shell are in good enough condition, they can be cleaned and a new BB installed. If the threads of the shell are damaged, then it would be a bit more complicated and deserve it's own question/answer.

This image (from Park Tool website) has the names of some BB parts. Even if it's not a perfect match, editing the question and using these terms would make the question clearer.