How to remove a seized bottom bracket from a titanium frame? I can't loosen it even with a long breaker bar.

If you are absolutely positive you know the direction of the threads, then an air operated impact wrench will do wonders.  I'm amazed at the difference when I remove threaded rear cassettes from my single speed wheels.  Removal by hand requires a long breaker bar, and a second person to hold the wheel from spinning.  Impact wrench is brizzzppp and done.  Its much easier to hold the tools tight to the work piece this way.  With long breaker bar, that's not so easy.

Again you need to know which direction is which.  (thumbs up to Daniel R. Hicks)


What is the purpose of the little wings on caliper brake pads I noticed that caliper brake pads (holders) have little wings on the bottom that aren't present on v-brake pads.

What is the purpose of these little wings?

Photo by RoboKaren. Released to Creative Commons by-sa.

This other photograph on Wikimedia commons that @ojs linked to of the classic 1984 Campagnolo Delta brakes shows a more exaggerated form of the 'wings':

They are to help guide the wheel/tire into place when you have to change the tire. Especially when in a hurry such as during a race.


Best place to shop for parts in Canada (used parts) What is the best place to buy bike components that will ship to Canada?  I would prefer a Canadian company or someone who ships within Canada to avoid large shipping costs and inport duty.

I am especially interested in buying used components.  Right now I am interested in buying:

Some non-indexed bar end shifters for my road bike
A mountain bike fork with disk breaks and no suspension

Where would be the best place to look for this?  I have tried my local craigslist postings but these items are too specific.  I have also looked in my local bike shop but buying these parts new will cost more than buying an entire new bike.  I like to do most of my own work and being a student I have a fairly small budget.

Where would you look for these parts?

Have a look at PinkBike's Buy/Sell pages.

This is a site for hard-core bikers, there are always parts of various qualities and conditions up for sale.


Preventing lamps being stolen / thieves' motivations My bicycle's front lamp has been stolen AGAIN. I thus far have spent over 100 Eur on bicycle lamps that can be slid onto a mount on the bike, and more on rechargeable batteries for them. This needs to stop but I need a solution where I don't need to carry the lamps with me. For this, I tried to think like a thief, but it just doesn't compute. Why the hell would someone steal a bicycle lamp!? It doesn't make any sense to me.

I glue the lamps to the mount so they cannot be removed by people still steal them. Sometimes I can see that someone tried to steal my lights (for example when they point straight up into the sky when I come back; someone obviously tried to yank it off but failed), so it provides some improvement, but my lights still get stolen. What do thieves do with lamps where half the mount is still glued to the lamp because all they were able to do is yank it off so hard that the mount ripped apart?

This isn't just a rant. I need a solution and I think it'll help me to know what they want so I can stop providing them a way to get what they want.

I found this answer to a somewhat related question which only mentions reuse and vandalism. It should be obvious that you can't easily reuse a lamp if you had to yank it off so hard it breaks the mount. Now I had my bike vandalized on several occasions (things obviously no one profits from like spokes kicked in) but the only thing that has ever been stolen from my bike are lamps (the front lamp more often than the taillight). This is despite the fact that you could easily steal other things. The linked answer mentions seats. My seat can be removed in about a second without any tools because it's held in place by a quick release. It's definitely something specific about lights in my case.

I've never had a problem like this with dynamo powered lights. While thieves seem to be interested in clip-on lights, they don't seem interested in lights that need a wrench to remove.

Of course, adding dynamo powered lights means adding a dynamo first, and it's important to take either a hub dynamo or a good bottle dynamo. The vast majority of bottle dynamo models is utter crap! The added advantage of dynamo powered lights is that you cannot forget to charge them, and they'll serve you well should you decide to ride through an entire night...


Can I use long reach calipers on my cyclocross bike? I've got cx bike(Centurion Cyclocross 4000) which I currently use only for commuting and riding long distances on a road. Is it possible to use some longreach caliper brakes on it (e.g. Shimano BR-650 or Tektro R538)?

I've just looked at the Centurion website and it's not clear from the pics or the German specs whether the frame and forks have caliper mounting holes. Look for a hole in the centre of the fork to take the caliper, and a corresponding one in the centre of the rear cross-brace above the wheel.

If those are there you can use caliper brakes of some kind, if you can get ones with the appropriate reach.

Bear in mind that you may also need to change the levers to pull a different amount of cable, or use some kind of adapter.


Is it normal Allen keys are loose fitting? I notice on my chinese made Norco that the keys are very loose fitting.
I know there are different sets of allens but I seem to remember them either fitting snugly or not at all. The reason this concerns me is
it feels like I could strip the hole especially on the brakes which
have to be tightened down well.

They all have some play in the fit. The target outside dimensions for the most common bike hex wrench sizes (4, 5, and 6mm) are all around .1mm less than the bores they fit in, which match the nominal sizes with a tolerance of I think +/-0.05mm-ish. That shouldn't lead you to feel they're "very" loose, but they typically aren't exactly snug. Very loose suggests using imperial aka fractional/SAE wrenches, whereas virtually all Allen bolts on bikes are metric. The only exceptions I've encountered are certain 90s BMX stems.

That it's Chinese is here nor there.


Ride on rightmost lane that goes straight or right yield to drivers? Sometimes I ride in the middle of a right most  lane that can go either straight or right.  Sometimes I get honked at red light cause drivers want me to move so they can pass me and make right turn.  Is it cool if I block the whole lane during red light? USA

I do this regularly biking in the US. Taking the lane at an intersection reduces many dangers at intersections. If there was a car in the lane that was going straight the cars behind would also not be able to turn right on red. At the light, you are moving at exactly the same speed as a stopped car going straight and so there is really no reason for you to not use the same amount of space.
I am not a lawyer and the exact laws around biking vary between states in the US so this is not legal advice. Though for reference my state would require me to ride "as far to the right as is safe/reasonable" so I believe that my suggestions follow this.
Also as an aside, cars turning right on red is really dangerous and shouldn't be a normal thing.


front luggage carrier for a single speed bike I built a Single speed bike based on a old Road bike frame.
What I want to do is to install a luggage carrier to the front for some daily transports (because i like the retro look of those carriers).
But I don't want it to be permanently installed on my bike if there's any way.

So, does anyone know a possibility for a (removable) luggage carrier for a Road bike frame?

Removable makes it unsafe, as it will jump up and down while riding, unless you can get any type of carrier that has a proper lock thingy.
Use a lid or straps to keep your stuff in the carrier, for that same reason, they jump like mad!


Do I need to plug internal cable routing ports? I have just ordered a OneUp Components 42T sprocket and a Race Face 30T Narrow/Wide single ring so that I can convert my 3x10 drive train into a 1x10.  This means that I'll be removing the front derailleur all together.  I have a carbon frame with internal cable routing so once I've removed the shifter cable there will be open "ports" in the frame.  Is it important to plug these ports?  What might happen if I don't plug them?  There is one where the cable enters at the top of the frame, and one under the bottom bracket where the cable exits.

I would plug them. If left open you will have the chance of water ,dirt, etc, inside the frame. The water and grit will eventually make its way to the bottom bracket. Even if the bearings are sealed it will still get on the threads of the bearing shell or threaded inset potentially making it difficult to remove.


Making the most of Edge 500 courses I want to make the most of this feature, and use it for navigation on pre-planned courses. I have used it two times now, and the experience was much different. The first time everything was ok, sometimes marked me off course briefly while I was riding on course but nothing terrible.

Second time, it was way off. It would show me on different location compared to the route very often. Very often the view was zoomed out too far, and it was not clear where the turns are as everything was smashed together. I am not sure what caused this difference in experience.

My question:

What steps do I need to take to make most of the courses feature?
Is there a way to avoid manually adding waypoints to turns, so that I can get turn directions? If not, what are the most reliable tools for creating routes with waypoints ? Any tips for these tools ?

Finally, I saw mentions of manually setting the zoom level on the course, but no clear description of how to do that.

I've had the same mixed results using the Edge 500 for courses.

It sounds like you used a TCX file for the first course, giving you a better auto-zoom level and accuracy, and maybe a GPX file on the second course, resulting in less accurate performance. Sometimes though, it seems the little 500 just doesn't have the accuracy of other models and strays off course.

To adjust the zoom level, page over to the map/course layout and press the power/light button. You'll see the zoom level is probably set to auto. Just use the up/down arrows to adjust the zoom level and hit enter when you're done.

Generating TCX files with ridewithgps.com seems to be the most popular way to chart a course and add cues and turns. Most popular routes already exist if you search for them.

For what it's worth, the newer models, 510, 520, 1000, etc, seem to have a much better grasp on your location ( and liekly extra processing power to help ) and throw up an off-course false alarm much less often, even under dense tree cover.


How much faster can i go after moving from 2x10 to a 3x10 gear setup? My 26" mountain bike currently has a 2x10 gear setup with SRAM components: a SRAM S-1250 crank with 38/24 chainrings, and a SRAM PG-1030, 10-speed, 11-36t cassette. I feel that when riding on non-technical dirt trails I am maxing out my drive-train, meaning that I am not able to accelerate beyond a certain speed when riding the 'hardest' gear.
I have been reading about the Shimano 3x10 system which may allow me to reach higher speeds, due to higher possible transfer ratios. So, how much faster can I with a 3x10 setup? please elaborate on the math in your answer...

Well, if you switch to 3 in front, and then make it a 52/38/24 set (equal steps) then your theoretical new maximum speed would be:

[new max]=52/38*[Your current max]

Currently at your top speed one revolution of your crank leads to 38/11th of a revolution of your rear wheel. This will become 52/11th or about 1.37 times as much.

This is not the whole story however. You probably know that wind resistant is much more of an issue at higher speeds than rolling resistance. So (unless you are really strong) your actual maximum will be quite a bit lower than the theoretical maximum calculated above. This tool allows you to set your speed or power output and calculate the other. If I assume your current max as 30kph, your bike weight at 9kg, your weight at 70kg (don't be offended, I'm just guessing), and you are on MTB tires and in the "hoods" position (whatever that is) then your power output at that speed would be about 220 Watt. With the extra chainring in front your theoretical maximum speed would be 41.1kph (all other variables being equal) but to attain it you would need to about 470 Watt! More than twice as much!

Obviously in your current situation you are not pedaling efficiently at your maximum speed because you are spinning your legs like crazy, but a 1.4 times speed gain is probably too much to hope for. As a test to see where you can get you could ask your friendly LBS owner if he'll lend you a bigger front chainring for a test ride and see if you can find out from that at what point you max out.


Are center lock rotors less likely to rub or resonate while riding than 6-bolt rotors? I use 6-bolts hub with 203mm rotor and despite it is well aligned and rub free sometimes when riding (even on flat surface) there is vibrations coming (I guess) from crankset and/or road enough to make rotor resonate a bit. This leads to rubbing against pad in audible manner.
This of course is not welcome, I don't even care so much about wear of the pads/rotor, but the delicate noise coming from rotor.
So I wonder -- is centerlock resonance free? Or maybe not 100% resonate free, but more stable in this regard than 6-bolts?

Intermittent rub that corresponds to load received by the frame or fork doesn't have anything to do with how stiff the rotor or its connection to the hub is. It's the fork or frame being flexed, not the rotor.
Usually the issue is caused by the air gap between the rotor and pads being too little, such that flex that would otherwise go unnoticed is causing rub. Causes can include rotor truth, poor caliper centering, piston stickiness issues, crooked wheel installation, poor parallelism of pad surfaces in the caliper, and/or poor brake mount surface alignment. Sometimes one sees a situation where none of those problems exist but rub is occurring anyway from the rider simply overloading the bike, but that's not very common.
Center lock versus 6-bolt is not a factor. On QR disc bikes, the stiffness of the hub axle can be a factor, however. In particular, going to a thru-bolt hub is one way that rub under load can be mitigated in those cases where it's happening when all of the other potential causes have been pursued. Thru-bolts add stiffness to QR forks and frames.


How to / is it possible to straighten a bent seatstay/chainstay on a steel frame? At home or inexpensively by a professional I have a Genesis Croix de Fer 20 (725 Chromoly) and crashed with my friend on his bike. On one side the back of the frame bent out so the wheel drops out, it is bent but not crumpled.

I would like to know about the options for fixing it either myself or by a pro without costing too much (I think I could get a new frameset for £350). I am based in Denmark

any help much appreciated I have attached a picture of the fram.

e

Rear triangle rear alignment of a steel frame is well within the scope of a home mechanic. There are professional tools available but functional versions can be made cheaply from lumber and generic hardware.

RJ the Bike Guy has some good videos on his YouTube channel (embedded below) that show how to measure how far the stays are out of alignment, how to re-align them and how to re-align the dropouts

You will of course have to make a determination as to whether your frame is too deformed to be safely re-aligned. Once you have determined how far the stays are out of alignment you can seek advice and make that decision.


Will any Shimano V brake fit any v brake lever and any v brake bike? I need to replace the V brake on this bike:

It uses Shimano EZ FIRE 40 brake levers, and has Shimano V brakes installed (Tektro TK837).

Can I replace these V brakes with any other V brakes available on the market (E.g. Shimano Deore BR-T780 XT V-brake), or are there compatibility issues to consider?

More generally, if a bike already has V brakes installed and working, can I just go ahead and fit any V brakes I find without having to worry about whether they will fit?

Yes, they all work together. Only exception is all mini V-brakes. They are not compatible with standard V-brakes.


Boardman road bike bottom bracket I recently purchased a boardman road bike and after 5 weeks as soon as you put effort into peddaling I am getting a squeaking noise from the bottom bracket, I took it back to halfords and they said it needs greasing every so often, is this an easy job to do and should I be doing at after only 5 weeks

It should not require greasing after only 5 weeks, unless it was not done originally.

A noise of that type can be caused by basically 4 things in the Bottom Bracket:

Loose or worn bearings - in this case unlikely because of the age of the BB
Loose or dry BB cups
Loose crank bolts or crank arms
Dry chain - not likely, given the stated fix by your shop.

Options 2 or 3 are likely given the fix described. Both would be repaired by removing, greasing and retorquing the BB.

The most likely cause after such a short time is that they were left loose or dry during assembly, and that the shop or mechanic was talking CYA.

But that is difficult to determine from several thousand miles away. You can be confident that the maintenance does not need to be performed every few weeks. Your twice yearly tune up should be enough.


B-screw adjustment in a derailleur with a spring in the upper pivot (Shimano RD-5800) I have tried to follow ParkTool adjustment tips for the B-screw of the rear derailleur (other company's tips are similar) , but I fail to detect the condition "the upper pulley rubs the largest cog".

I have completely unscrew (removed) the B-screw, but even shifting from the second largest to the largest cog shows no interference.

I can, of course, make the upper pulley rub the cog, if I manually rotate the rear derailleur towards the cog. The problem is that the adjustment of the B-screw cannot reproduce this symptom.

Is that normal, or should I worry my rear derailleur was mal-installed?

For your information, the instructions I have followed for the B-screw adjustment are the following:

http://www.parktool.com/blog/repair-help/rear-derailleur-adjustment#article-section-5

EDIT: I think it may be a chain length problem, as if the tension was reduced (longer chain), the upper pulley might touch the cog depending on B-screw adjustments. I will check the equations to calculate the chain length and compare against the existing chain.

Well, I have removed the derailleur from the hanger, put the B-screw half-way in, reattached the rear derailleur, and the noise of a maladjusted B-screw appears.

I have followed ParkTool guidelines, and now it is properly adjusted: 1/4 of turn from the cassette/upper pulley rubbing position.


How to test-ride a full-suspension bike? I am looking for a MTB, but am unsure how to measure if the frame would fit me.

I haven't had a full-suspension bike. Furthermore, I am pretty sure MTBs perform entirely differently in the city and when going down a rocky track. My previous bike was small, short and awkward on pavement, but incredibly stable on the descents.

When test-riding, I very much doubt that any shop will let me ride for a whole day. And from doing a couple of circles around the shop, rushing a couple of curbs, feathering or squeezing the brakes and doing a jump or two there is hardly any feel as to what riding will be like, when I get used to the bike.

Kind of like with new shoes - at the start, every model is "awkward", as one has not gotten used to it.

I will ask the guys at the shop to help me with fitting, of course, but concerning the test ride - how do I do it correctly? What information is most essential to gather during the very short ride and how do I do that?

Bike shops have a special test-bikes to be lent for a whole day or even a weekend. I tested Specialized, Scott and RB for the whole weekend this way.

You will pay them a refundable deposit (20-80% of price of the bike - depends on the shop). Some of them will charge you a little for cleaning/service or whatever. This may vary across the countries; I have experiences only with mine, but Specialized and Scott are international brands, so I expect similar offers around.

This is an answer for the topic, not your last question, but I think this is the right way to choose a bike.

There are also test-centres in some Single-tracks where you can borrow a bike for couple of rides. But they have a limited offer of models there.
Or some shops organize test-events near nice places to ride with many bikes to try if you book in advance.

This is the best way to choose a bike. I was in the same situation as you. On the first test I borrowed two bikes from one Shop (RB): similar hard-tail and full-suspension and rode it with my friend exchanging couple of times to discover if is it even worth to invest to full suspension. It was quite convincing. Then I tested couple of other models of brands above for weekends. It's a fun to have a different new bike on every weekend. From these tests I came with very certain conclusion what I like the most.


Cuyuna Lakes, MN Camping? Has anyone rode the trails at Cuyuna Lakes in Ironton, Minnesota?

Wondering if there is tent camping at the base of any of the trail systems that a guy can literally ride into camp at the bottom ?

If so, can you give me some advice? Where to go...best place to grab...heads up about anything... etc.

Thanks stackers!

Based on a quick search on Google, I was able to find Portsmouth Campground, which looks to be pretty close to the trails. They also have yurts available, which might be nice as they aren't too expensive and you might even be able to fit your bike inside if you didn't have too many people.


My Gears Are not Shifting Well my gears are not shifting well. i can only shift from 1st to 2nd...i don't know what is the problem
i have shimano revoshift gear enter image description here
here are some images

If you can't get out of the lowest (easiest) gears then something is stopping the cable from releasing. There could be a number of reasons for this. The shifter on the handlebars might not be working properly, something may be caught on the cable and pulling it, the cable could be frayed and is snagging on something, or the rear dérailleur could be jammed.

So you should do some diagnostic tests: if you try to put it into highest (fastest) gear and the cable goes slack but the rear dérailleur doesn't move then it's not the shifter, so you can rule that out. If you undo the nut that holds on the cable to the dérailleur and the dérailleur moves, then it's the cable, and if it doesn't then it's the probably the dérailleur.


Is it possible to fit a 26" fork to a 29er bike frame I want to buy a cheap frame and put parts from my old 26" (wheel and fork) and 15" (frame). Is this possible.

Update: Fixed bad calculation for the BB drop, thanks to @mattnz.
Physically, it may be possible to fit the fork alone. But the resulting bicycle will be dangerous to ride, for at least two reasons.

The wheels with 26" rims vs 29" rims  are at least (622 - 559)/2 = 31.5 mm or 1¼ inch lower, meaning everything will be lower, including the bottom bracket and the pedals in their lowest position. This means you will have much greater chance to scratch the road or trail when pedaling. Even if it won't touch the ground when you ride the straight line, at cornering the whole bike leans, and pedals go even lower. An unexpected pedal-to-ground contact, especially when cornering, can kick the rider out of the saddle.

What size of wheel will you put at the back? If it would be a 29" one, the bike will look very odd, a "reverse mullet" of sorts. Besides the looks, a bigger wheel at the back will increase the steering angle, which in general corresponds to more sensitive steering. The bottom bracket will still become lower, although at lesser extent. The bike will be twitchy to control. If it would be a 26" wheel at the back to match the front wheel, see the lower bottom bracket argument above. Plus, if you have a frame for rim brakes, they won't work because they are designed for a specific diameter of the rim.

Using 26" wheels in a frame designed around 29" ones is really not recommended unless you can run all the numbers yourself for the specific frame and are confident that it will work, and you understand how the resulting bicycle geometry changes affect ride characteristics. As an example, for frames designed around 27.5" wheels, some people did use 26" wheels with them. But then one needed extra wide/high tires to compensate for the rim diameter difference. Wider tires are less likely to fit into the frame/fork without rubbing, so there are limits to this as well.
The difference between 29" and 26" wheel is just too big for this trick to work on regular bicycle frames. Some fatbike frames allow even that, e.g. one of my bikes accepts both wheels with 26"×4.8" and 29"×3", as confirmed by its manufacturer. But that is fairy unusual.


What is the origin of BSO - and is it internationally recognized? Who is the first person who came up with the appellation, "Bicycle Shaped Object" (BSO) referring to very inexpensive and very poorly built bicycles sold through mass-market department stores?

Bonus question: And is it international? We use BSO in America and I've heard b.se members from Australia and New Zealand use it, but is it used in the UK and Canada? What do people in France or Japan or other countries call BSOs?

If the bonus question makes this question too broad then I'll withdraw the bonus and make it a separate question.

In German, I have never heard anything similar. I think one reason is that everyday cycling is more common and many people have a cheap, battered bike to get to the railway station or the local shop, so you could argue that most bicycles you see in town would be seen as BSOs by UK cyclists. It doesn't make sense to invent a new term for something that is common and already has a name.

When you observe bikes in town, in the UK (where I live now) you can rather clearly see two distinct groups: high-end bikes for the sports market (and people dressed accordingly) versus really cheap ones (often students in uni towns). In Germany it's much more a continuous spectrum with a lot of middle ground of various urban bikes, so it would be difficult to draw a boundary.

Most people buy bikes in the local bike shops, but shops tend to have a wide variety from cheap, simple, factory-built ones to high-end custom-built, so the fact that they are sold in LBSs isn't necessarily a criterium for quality or price.

Another factor is that "BSO" is a term that is a bit arrogant and derogatory, sends the message: "You are not doing it properly", which is what bike advocacy groups really want to avoid. In Germany, cycling is very much seen and promoted as everyday activity, and the cycling groups want to avoid terminology that would people off. It's better if people cycle on a cheap bike than not cycle at all. It's possible that the cycling sports community in Germany has derogatory terms for non-sportists, but I don't think it's common outside. Again, in UK the community is different and more sports-oriented (although that's beginning to change, in the last 5 years or so).


Is a bigger wheel likely to get fewer flats? Someone suggested recently that rather than using a fatter tyre in my search for fewer flats, I could use bigger wheels. Specifically, that switching from 700c to 27" (622 to 630) would make a detectable difference. Since I currently use 406 wheels on most of my bikes, switching to even 622 wheels would obviously make a huge difference... if this is correct.

What's the mechanism for the larger wheel getting fewer flats?

To clarify: I can't think of a mechanism, and I doubt that this theory is correct. So answers that talk about other causes are off topic, and if you want to show that this is wrong you need to demonstrate that using research or logic. I already think this theory is wrong, what I want are facts. And FWIW, changing from ISO 406 wheels to 622 or 630 means a complete change of bike.

One possible mechanism that occurs to me is that the larger tyre may hit fewer small pieces of glass because it rides higher over corrugations on the road.

Using my well-renowned skills with paint.net I give you the following conceptual diagram:

The black is the road surface, magnified and exaggerated to show the normal corrugations. Not to scale (or in proportion) are two different sized bike wheels. Note that the green one hits the red shard of glass while the larger one doesn't.

The puncture mechanism being affected is that contact with the glass adheres it to the tyre either through moisture on a wet road or just a tiny point entry to the rubber as shown below. Once adhered every further contact with the road might push it further into the tyre, eventually resulting in a puncture. But the larger wheel rides higher over small bumps, so comes in contact with fewer small shards since they tend to sit at the bottom of the corrugations.

But the size difference is small. Assuming 23mm tyres on both the ISO 622 and 630 wheels the outside diameters will be approximately
668mm   and 676mm (via BikeCalc), so at best the larger wheel will be 668/676 = 98.8% as likely to get a puncture by this mechanism. But compared to a 406 wheel at 497mm OD (with a 23mm tyre, unlikely though that is) the ratio is 73.5% (less than 3/4 as many punctures... of the ones that happen by this mechanism).

I doubt that a 1% reduction in frequency of one particular mechanism would be detectable, even if that was the dominant mechanism for getting punctures. I ride about 1.5 hours a day, 5 days a week, and get 2-5 punctures a year. Dropping that by 1% would mean I'd get one fewer puncture every 20 years (at best) making it 39-99 punctures instead of 40-100. The effect is so far down in the noise that it would be undetectable.

Further minimising the effect, most of my punctures are via bigger objects. Recently they've been the shaft of a pop rivet (622x28 non-puncture resistant tyre) and a carpet tack (406 marathon plus), with the last glass shard puncture being late last year (406 marathon). So in real life it's might only be a 1% reduction in 1/3 of the punctures.


The master link that came with my chain won't fit I have this master link that came with my chain (Snap On type). In the first picture it is distinctly the one on the left - not a spring clip.

Try as I might - it doesn't seem to be long enough? Do I need to use those funky chain pliers for it? How much can I compress that link? Thanks.

You need to bend the chain. Look at this link (PDF) for the Connex Snap On which is the same idea. The PDF is reproduced below in case the thing goes down.

As an aside, you normally can get an alternative standard quick link (like a SRAM 8 speed powerlink) for these chains, rather than the Snap on type.


Flared drop bars making my wrists numb, so am I using them wrong? I bought a Fuji Jari that comes with flared (25-degree) bars. When I ride, my hands go numb within two miles even though I've been to a fitter. I've found that to keep my wrists straight, I have to spread my elbows out ridiclously, otherwise no matter how I hold the bars, I end up with my wrists pointing outward after a few revolutions. I'm trying to decide whether the problem is the flaring and I just need straight drop bars, or whether I'm too close to them and so my wrist bending is inevitable.

Now I realize no one can really diagnose this blind, so what I want to ask this group is whether there is anyone riding a road/gravel bike with flared drop bars who finds them very comfortable, or if many people here have had similar issues?

Warning: As pointed out in comments the speed at which you develop numbness suggests a more serious lurking issue that the change in position may be setting off, it could be worth seeing a doctor as it sounds like you have a lot of inflammation.

  so what I want to ask this group is whether there is anyone riding a road/gravel bike with flared drop bars who finds them very comfortable, or if many people here have had similar issues?

I have been using flared bars for about 4-5 years now on my commuter (12 and 16 degrees). I personally find them quite comfortable on my longish commute (~1.5 hr a day). They took some time to adapt to but I found they afforded improved breathing and shoulders position, especially as I also adapted my fit to better suite the bars. Compared to regular drop bars, I find flared bars are more suited to a  upright + shorter riding position where you set your shoulders back (similar to standing) open up your chest and flair out your elbows a lot more. I even went with a bar that was 2 cm wider than my more aggressive “fast” road fit, as the flare seemed to suite a more wider overall arm position. All in all, I find the wider more upright position is quite relaxing for long rides and encourages you to support proportional less of your weight with your hands and wrists, compared to a more classical road fit.

  I've found that to keep my wrists straight, I have to spread my elbows out ridiculously, otherwise no matter how I hold the bars, I end up with my wrists pointing outward after a few revolutions. I'm trying to decide whether the problem is the flaring and I just need straight drop bars, or whether I'm too close to them and so my wrist bending is inevitable.

The fact you are falling into a pattern of pointing your wrists out, rather than your elbows, is concerning and probably isn't helping the numbness. If anything I would hazard a guess that it is a driver behind your numbness. As you point out in your question flared bars encourage a very wide elbow and arm position, bringing your elbows in means that you need to compromise on your wrist position, which is not ideal for extended periods.

If you do not like, or cannot adapt to having your elbows flared out, then you may need to switch to a regular low flare drop bar. That said, you can also try working on your riding position by focusing on keeping your elbows flared and your wrists in a more neutral position. You may also trying a more of an upright position, as it is more natural to ride with flared out elbows if you are more upright.

Finally, position changes can take time and may not feel "intuitive" at first, especially if you have spent a lot of time in a more classical aggressive road position.


Can I get my sprinting ability back? At the end of January this year I purchased a power meter in an attempt to improve my training and general speed. I also performed the obligatory barrage of tests for 5 second, 1 minute, 5 minute and functional threshold power.

The results where not unsurprising but my peak one second power was. On two different occasions I recorded a 1853 watt peak and 1618 watt peak (with two weeks separating each tests). Upon seeing this I almost sent the power meter back as I just assumed the numbers were way out of my league and thus wrong. Some one later told me not to focus on the actual number as its of very little consequence when compared to other peoples?

At the time I had just finished 7 cyclo cross races and later on found out that my Shimano cranks (and stages power meter) had the wrong bottom bracket (causing the cranks to 'rock' from side to side) which could be the reason for the anomalous results. I then went into training my early base period and left training my sprint until a week ago. The highest peak test I have achieved since return is 1213 watts, would it be sensible to think I can retain that peak power again or is the possibility of those two peaks being bad data just too high?

Bad data, no question whatsoever. Muscle fatigue develops quite rapidly, but even so there is minimal decrease in power for at least a handful of seconds. (Indeed, even the fitted curve you've shown seems to be in error, likely as a result of the way GC's fitting algorithm will chase "noise".)


What kind of wheels need different nipple for front vs. rear? I'm shopping for spoke nipples and I see some described as specifically for front or for rear.  Is this just a marketing tactic, or do some wheels need different ones like this?

Those are Motorcycle spoke nipples. Bicycles can have different spokes and nipples between the front and rear wheels but there is no standard.


What to do after an accident? This morning I almost witnessed an accident. I was a couple of hundred metres behind the incident but arrived at the scene when a pedestrian was picking a bike from the middle of the road, a distraught driver was parking his van and a cyclist was lying on the pavement very dazed and grazed.

Several pedestrians stopped, one called an ambulance, the van driver put a jacket under the cyclist's head for comfort, but otherwise we didn't move him, we kept him talking, he wasn't complaining of cold. He did want to know about his bike, he was more worried about it than his bashed up leg.

But what should we have done? Did we miss out anything crucial? Do we do wrong?

The highway code has some advice on First Aid on the Road. It says:

1. Deal with danger - the cyclist was on the pavement and the van was parked, so you did this.

2. Get help - an ambulance was called, so you did this.

3. Help those involved - you didn't move the cyclist and you kept him comfortable, so you did this.

4. Provide emergency care - you don't mention what injuries the cyclist had, but it sounds like you didn't need to do this.

I don't think you missed anything crucial, assuming the cyclist didn't have serious injuries (e.g. heavy bleeding).


Bike lights with beam cut-off to avoid dazzling drivers? Are there any bike headlights available that have a cut-off similar to a car's low beams, designed to avoid glare for other drivers? I am using the Light in Motion Urban 400 and while it's plenty bright, it blinds oncoming drivers if aimed normally. In traffic I have to aim the hotspot very low, basically defeating the purpose of having a pricy, bright LED light.

Are there modifications that can be done to the existing light, like blocking part of the reflector that is responsible for sending light upwards? (It's a single LED with a simple paraboloid reflector) Reading about the complexity of the design and regulations for car headlights, this seems unlikely, but I'd love to be wrong.

Alternatively, I am looking for recommendations for a better headlight. The Specialized Flux and the older Phillips SafeRide 80 seem to fit the bill. Not sure how bright the Phillips is with 220 lumens, but it meets German regulations so surely it has a great beam shape.

I have actually dramatically improved the cutoff on my 1200 lumen dual LED (just for reference) with a sort of brim made out of aluminium plate.  On road I run it on minimum brightness (guessing about 1/4 -- 1/3 power). On pitch dark bike paths I do change the angle a little as well as turning up the brightness.

Super-speedy sketch (go inkscape!):

The light body is about 60mm long, and the reflector is in approximately the right proportions.  I mocked it up with cardboard first, before using some 1mm plate - it's tucked away under the bars, under a front bag mount and all edge and corners are nicely rounded off.

The mounting underneath the handlebar is another issue -- overly reflective silver-grey brake and gear cables right in front of the light if it sat on top of the bars.

It's not quite as good as it was before I tweaked the handlebar angle. On (slight) riser bars using the riser as intended I had it tipped up on the left to illuminate roadside signs (UK).  I've twisted the bars so the rise points forwards at about 45° and the aim isn't quite what I'd like.

I promised pictures:

Side view

Front view

Illumination pattern (high ambient light levels)


How to wash a bike properly? I use my bicycle in a typical urban commute setting. No extreme MTB, but it still accumulates some dust and grime.

How should I wash my bicycle?

Cycling Tips has some useful pointers.

To summarize:

Degrease the drivetrain.
Wash the degreaser off the drivetrain with the brush and sponge.
Wash the rest of the bike with soapy water and the sponge.
Rinse the bike off with the clean
water and sponge (or a low pressure
hose).
You can dry the bike by wiping it
down with a cloth or let it air dry.
It’s a matter of preference.
Finish the frame off with Armor-All
or give a light wipe with silicon
spray to deter the next lot of mud or
dust from sticking to the frame too
quickly.  For obvious reasons don’t
wipe on the handlebars, brake hoods,
saddle, or wheels.


Is there a Campagnolo / Shimano compatibility issue for friction shift systems? I know that for indexed systems, mixing campy and shimano parts is a no-no. Does the same hold for friction drive trains?

The reason I ask is that I've never worked on campy parts before and I'm thinking of picking of an old Italian frame with a mix of campy and ofmega components with no wheels and I need to know what kind of wheels I will need.

In general, no.

Campy, Shimano, and Suntour (and other) friction shift systems are compatible because where the chain lands is up to you.

There are some caveats that you'll have to resolve with trial and error. In particular some rear derailleurs have "longer reach" than others. You may not be able to shift to the largest cog on some freewheels if the derailleur is short (intended for racing). But that is not specific to friction systems.

You'll get the best results from friction mode systems if you stick with down-tube levers. Of course, these are compatible across vendors and some indexed levers even have a selectable "friction mode".

Finally, it is posssible to mix campy and shimano indexed shifter/cogs if you use an adaptor. I use a j-tek and it works fine.


What to substitute a lost pedal dust cap with? I am working on my 90s Raleigh mtb (it's awesome), where one of the pedal dust caps was lost. Subsequently, the pedal without one had much more sand inside, and is in worse shape overall. As I'm finishing maintenance, I want to fix this, so, do you have any suggestions on the substitutes? My first instinct was to try a spare bar end cap, but it's much larger in diameter. Maybe I can use something small, and add a lot of plumber's tape to make it fit, but I can't think of anything right now.
Somewhere on forums people suggest coins or just no caps at all, but it doesn't sound right to me. I'll leave coins as last resort though.

By the time you have driven around town looking for a suitable sized dust cap, new Pedals might even work out cheaper.
One option could be use the pedal itself as a mold to make one from a silicon sealer.
Local hardware store will have a range of plastic end caps for things like curtain rods chair legs along with other and general hardware purposes.  You might find a suitable sized item there. Its the kind of thing an LBS might have in a box of bits.


Do Master Link pliers help with SS / fixie chain assembly? A followup to my own question, seeking specific help.  I'd like to know if anyone is using a set of "master link pliers" (something like Park's MLP-1 MLP-1.2, or try this search) to help them with derailer-free chain work?

I have an IGH without a derailer or tensioner, so my chain line resembles a fixie / SS setup.  The chain has an ok amount of tension, but without a derailer, generating enough slack in the chain to both remove and reattach the power link isn't happening unless I remove the rear wheel.  Will a tool like the Park MLP-1 allow me to get the chain off and back on again for regular cleaning without forcing me to remove the rear wheel?

Thanks oodles!

If you're looking for a way to get the chain off without loosening the wheel then this won't help you. This tool require there to be enough slack in the chain to pull two links together. I'd say the links move about 5mm in order to break the link. I would recommend having this much slack in the chain normally.

What you want is a 3 piece master link that uses a c-clip to hold it together. These don't require any slack in the chain to disassemble. They seem to be more common for 1/8" chains though.


What are the physical advantages of riding a single speed with higher chainrings? Ever since my aero road bike was stolen, I have been riding a cheap single  speed bike on average 6 miles a day. The crankset was cheap and I recently switched to Sram Ominium 48t vs what the bike had 44t.

Overall the bike is faster but the chainring is on the larger side and i constantly have to standup if i am going up hill.

I feel like my lower back is getting stronger, but I am wondering what the physical advantages of a higher chainring on a single speed.

The efficiency of chain transmission decreases if one of the cogs has very low tooth count. Track cyclists often use high gear ratios, and large chainrings are used so that a reasonable sized cog can be used. Another reason is that when the cogs are larger, changing to one tooth larger or smaller cog changes gear ratio a smaller amount than with smaller cogs, so larger cogs allow finer tuning of the gear ratio. Both benefits are small, but in racing you use all advantages you can get.

For street singlespeed, the main reason to use large chainwheel is to make the bike look like track bike (isn't this why you bought the Omniums to begin with?). The other popular choice is 42t, because that comes standard with old road cranks and produces nice gear ratio for street use in combination with track cog.


Sudden loss of air on tubless tyre, and now it won't inflate Finding bike answers on the internet is really hard when you have no idea what you're looking for, so I'm sorry if I'm asking a ridiculous question here.

Cycling back today I went over a bump in the pavement and heard a noise come from my front tubeless tyre. Sure enough when I got off and felt the front it was quite deflated. Upon getting back home I've checked the tyre over and can't find any punctures. I then tried to reinflate it (a presta valve, which I have unscrewed and attached my floor pump to) but the valve won't take any air. When I get a proper seal and pump the air appears to go in but I think I feel it escaping from where the valve stem joins to the rim.

I'm suspecting that the valve might be busted over the bump, but I'm not sure how you can tell. Is it possible to just replace the valve in this case?

I've looked a lot around inflating tubeless tyres from scratch and the general feeling I'm getting is that it's very difficult, you should generally use a compressor. Is this the same for reinflating tyres you are not reseating? And how would I tell if the valve is dead or if I just can't get enough air behind it?

Also the valve is entirely depressible into the wheel frame (pretty much). Is that normal in the case of there being no pressure?

This is a bike I got from the shop with the intention of learning more about it as I go, and I guess here we are learning about it.

Thanks in advance

Your valve should NOT be depressible into the rim.  You should have a presta ring screwed in it, else nothing is retaining the valve and your air probably leaks from there!

If its not the case, if the tyre is seated correctly on your rim, inflating it with a pump should be easy.  Maybe you have a dent on your rim where your air is leaking.

Yes absolutely, you can get a new valve for tubeless tire.

A good way to find where your air is leaking from is spraying soapy water around and check if an area makes bubbles.  It will tell you exaclty where your leak is from.

Cheers


Gmc Denali - good bike on a 200 budget? Alright, so, please, don't flame me for buying a budget bike. My dad recently passed away, and i've been riding his bike. It was a hybrid mountain/road bike. As it slowly died, and i bent the rear axle (Don't ask me how, i don't ride it hard) i debated buying a new bike. I have a few friends with the Denali, and, while they won't let me try it, it looks to be a good bike. One of them has had it for over a year, prompting me to consider it. Personally, i don't have the money for a big budget bike, and only have around $200 to spend. I also pop on and off curbs, and am wondering if that will be much of a problem. Is it worth buying? Will it stand up to my antics? I only weigh 155 Lbs and am a fan of speed. I'm 5'8" but am looking to buy the one intended for much larger people (6'2"-6'5") as i am used to that on my dad's bike. (Plus, i'm only 16, i might get a little bit taller). Biking is pretty much my life, I do it daily. But my old bike is not a road bike, it was a hybrid and is 40 lbs. Is it worth the upgrade? I'd like to get a higher cruising speed as well as a higher top speed. I'd also like to be able to jump on and off curbs if need be. (I've been hit on my bike riding on the road a few times)

"As it slowly died, and i bent the rear axle (Don't ask me how, i don't ride it hard) i debated buying a new bike"

Hmmm… If the bent axle is the only major problem the bike has (by "it slowly died" I take you to mean that it was developing other less-serious problems too), if I were you I would do an overhaul and continue with the hybrid.

I don't know if you have the knowledge/experience it would take to do such an overhaul, but if you were willing to put up $200 in quality components and elbow grease, you could probably turn your hybrid into something that's significantly better than any new $200 bike.

If you decide to purchase a bicycle, definitely buy used. Don't get the Denali. A used $200 road bike will last longer.


Is it safe to ride a racing road bike in very wet weather? I'm used to riding on a MTB, but since I've got a new road bike, I'm quite paranoid about the slick tyres. How good are they in wet weather? I'm scared of braking too hard, or even just turning!!

They're fine. I live outside of Vancouver so I'm already riding in wet a few days a week some weeks. Just this morning I was coming down the backside of a climb at 70km and they were totally secure.

Since the tires are so narrow they don't suffer from hydroplaning. The biggest thing to worry about is painted lines and manhole covers (or other metal covers on the road). Both are very slick when wet. I've always been careful but I know a number of other riders that have gone down cornering hard on both types of surfaces.

You're right to leave yourself extra room to brake. Also don't forget to account for reduced visibility for both you and cars.


Why is it called a "timing chain" Why is the chain connecting the front and rear cranks of a tandem called a timing chain.  This brings to mind big-block V8s and leaky timing chain covers that plagued my younger years.

What's the history of this term?

The Timing chain helps keep the front and back riders pedals rotating at the same time.  Depending on your preferences you can set them as "in phase" where both the front and back cranks are at the same point in the rotation, or as "out of phase" where the front and back cranks are offset by 90 degrees. This is advantageous as when one of the riders reaches the dead point (where the cranks are vertical), the other set of cranks is at horizontal allowing good power transfer.  You can set up different levels of out of phase. You can set it up so that one rider is only a few teeth ahead of the other rider, so that both riders aren't in a dead zone, but the pedals are more or less aligned.

You can even set up both riders with different size chain rings, which would allow one rider to pedal at a faster cadence than the other rider.  This presents problems when cornering, as it's hard to get the pedals into the proper position so that neither the front nor the back will hit the ground.

Sources and more info:
Pedal Setup
Poll: In Phase vs. Out Of Phase
Out Of Phase Cranks


Reducing Bulk on a touring trip I'm doing a self contained touring trip, I have a 5 piece set of ortlieb bags (handlebars, 2 front rollers, 2 back rollers). I also plan on putting my tent on my back rack. I'm not doing this in a competitive manner. I'm just looking to have some fun on a 2 week tour.

Recently, in another thread, I became aware that "bulk" can be more of a concern than weight. I'm wondering a few things,

What exactly is bulk? Are we just talking aerodynamics?
How would one go about reducing bulk when using panniers?
Any tips for reducing bulk in general?
How important would you rank bulk compared to weight, comfort, etc. (given my parameters of prioritizing fun over serious competition)

'Bulk' is mostly about whether all of your luggage will fit in your bags. ie is the volume of your luggage less than the capacity of your bags. So it depends on how much stuff you want to take, and how big your panniers are.

Aerodynamics doesn't really matter for touring. Unless you are cycling rather fast, or it is very windy. Usually the weight of your bike and luggage will make more difference to your speed and effort required.

For reducing bulk, the main thing is taking less stuff. It also depends on how you pack it. eg if clothes are folded properly, they will be less bulky. Some things can be squashed smaller, eg sleeping bags. Compression bags can help with this.

It is worth leaving some spare space in your bags. You may want to buy things along the way. eg food supplies can be surprisingly bulky. Or any essential gear you find is missing, or any souvenirs you want to take home. Also after packing and unpacking a few times, you will probably find things don't fit as neatly, so end up taking more space.

Its up to you how you much you want to carry. Carrying lots of stuff will slow you down a bit while cycling, so you won't cover as much distance. And it may affect the handling of the bike, so its not as fun to ride. On the other hand, it is nice to be comfortable while camping, and have all of the kit you might want.


What symptoms can I expect from two broken teeth on a chainring? Dealing with chain skipping (but mostly on the smaller chainrings, truth be told) I've wondered how these affect the riding and how many problems and what kind should i expect from these two broken teeth on the big plate, and close together as well:

The only issues will be directly observed, i.e. either it will mis-shift, over-shift/drop the chain, or not. These don't look like proper ramp teeth which do resemble broken ones, except they're usually spaced 2 or 4 evenly around the ring. The wear looks advanced enough that you really have no excuse not to just get another new or less worn ring and avoid problems.


Raleigh AT20 series bottom bracket affects derailleur I took out the bottom bracket to clean it etc taking off the pedal shafts etc - and when it came to putting it back - the front derailleur was well out of adjustment - Have I done something wrong>- This is the first time I have taken out a bottom bracket. Thanks Ben

I'm assuming this is a 3 piece Shimano sealed-cartridge square-taper style bottom bracket, since you didn't provide any further info, and that fits the price/style/vintage of that bike. (for more on bottom bracket styles, read the always useful Sheldon Brown site). Additionally, how is the derailleur out of adjustment? Is it a cable tension issue? Is it not a front derailleur position (yaw, height) issue from getting moved during the operation?

Assuming you did not alter the position of the front derailleur, and following my assumption of the BB type, you probably did not install your bottom bracket properly as @Hicks was getting at. Most 3 piece bottom brackets have 2 cups with the threading, and the bearing/spindle set itself which fits inside the cups. (If not, the drive-side threading is probably fixed to the bearing/spindle assembly (but also possibly not)). These bottom brackets are generally larger than the bottom bracket shell of the frame (depending on manufacturer), which means the bottom bracket's threading will be protruding from at least one side of the bike. If the drive-side of the crank spindle protrudes further from the bottom bracket shell than it should, your front derailleur will always be off by that distance.

When installing the bottom bracket, you must fully thread the drive side first so that it matches flush with the bottom bracket shell of the frame. Then you can thread the non-drive side (for further instructions, see Park Tools Guide. Re-attach crank-arms, recombombulate bicycle, etc.

After following this process, your front shifting may still be off--the factory or mechanic that built your bike may have adjusted the front derailleur with the bottom bracket not fully-threaded in on the drive side. If it's still not shifting correctly I'd suggest learning to adjust your front derailleur, because that's a much more worthwhile endeavor than trying to improperly install the bottom-bracket exactly as it was when you got it/had it repaired last.


What size frame is right for me? I have an inseam of around 26 1/2 inches (without shoes). Would a 47cm frame fit me? If not what would the correct frame size be? I'm looking for a hybrid (or road) bike.

Really, the only way to make sure you get a good fit is to sit on and test ride some bikes. There are many variables that sizing guides can't take into account, such as proportions of the rider's arms legs and torsos, and preferred riding position. Additionally, the common seat tube measurement isn't very standardized across manufacturers and frame styles

Getting the right size bike is worth putting some effort into. Presumably you want an bike you can enjoy riding, You won't enjoy riding an incorrectly sized bike. Even if you can manage one visit to a good bike shop to try a couple bikes would probably be worth it.

All of that said, if you really need to buy online, you definitely need at least a 'small' size. Look for manufacturer's size guides of bikes you are considering and for good return policies in case your estimate is off.


Another mysterious frame identification I've got another mystery at my hands. This time this 26.6mm seatpost (although i'm not with a paquimeter on my hands, a 26.8mm one almost fits is), italian thread bb. By scratching the dropouts I couldn't find any visible stamps and I have no idea of any components and fork that it came originally. I can read the serial number as 903273 and have never seen those lugs before, does anyone have any idea?

here are the pics

The lugs don't look familiar. It has horizontal dropouts and full length brake cable housing so that dates it to sometime prior to the mid-80s. The fork is 100% not original to the frame. It has bottle braze-ons so it's likely made sometime after the mid-70s. The one peculiar thing is that it has bottle braze-ons but not shift lever braze-ons (and this bike most definitely predates integrated brake/shift levers such as STI or Ergo) It also has brazed on cable guides for the derailleur cables. I'm guessing the dropouts are 126mm spacing?

It could well have been made for a 26.8 post. That rattle can paint job could be compromising the fit and it's also not unusual to have the seat tube become slightly ovalized due to over heating the seat lug during assembly.


What does "modulate" mean when referring to brakes? Often in a review of brakes, or an article talking about braking the author will use the term "modulate." E.g. "The brake modulates well" or "Modulate your front brake."

What exactly does this term refer to?

Brake modulation how much fine control you have to apply a range of braking power distributed over the pull of your brake levers.

No modulation is basically no braking vs wheel locking.  Having low modulation will mean it's hard to feather the brakes and you can only really lock up the pads.  Too much modulation means you will bottom out on the levers before you lock up on the wheels. Ideal modulation gives you access to the whole range of braking power desired and allows you to apply it evenly across the range of the brake lever, giving you fine control over feathering the brakes, stopping firmly, or locking the wheel.

via simkinsdesigns.com/modulation.htm


What is best for your brakes when stopping at the bottom of the hill? You are at the top of a hill and want to stop at the bottom. What is best for your brakes so you don't wear them down:

brake continuously; or
brake when you reach the bottom?

In terms of wearing out the brakes, they will wear less when you brake at the bottom.
When you descend a hill you have a fixed amount of energy to lose, and when you descend at a higher speed, a larger proportion of that energy is lost to wind resistance.

Practically however, brake pads/blocks tend to last a long time and are cheap to replace, wear is not really something to consider too much.  It's better to descend safely at a speed you feel comfortable with.


Should I buy this bike with a dent in the top tube? Is it safe? I'm considering buying this used steel-frame bike. But the top tube has a small dent (about one-third of the way from the saddle). Is this a problem? I plan to use it daily (~6-7mi) for commuting to work.

Here's the link: https://www.gumtree.com/p/bicycles/genesis-cdf-racer-/1361247559

A small dent in a steel frame should not be a problem. However, It's hard to see how big that dent is in the pictures provided. Damage to the top tube may indicate that something heavy fell on the bike. If the top tube is bent then the frame will be weakened.

Don't buy this bike without inspecting it bike personally. If the dent is small use it as leverage to negotiate the price down. Check for other damage too.


Suspension forks on child/youth bicycle for road ringing good? When riding only roads and well maintained trails, does it make any sense to have a suspension fork on a children's bike (10-12 years)?

My initial gut feeling is to say no as it just adds weight and complexity to the bicycle.  But I don't have any experience to back this up.

The short answer is no. Cheap suspension forks do only add weight and complexity as you say, and give very little actual suspension. My personal experience with cheap forks for adult bikes are that they can take away some road chatter, but with the increased weight and complexity it is hardly worth it.

The only worthwhile reason to have it must be that the kid likes the look and wants to ride the bike more because a suspension fork looks cool.


How tight should brakes and shifters be on the handlebars? How tight should handlebar components be?

Here it's said 6-8Nm. However, I don't own a torque wrench at that range.

Should the brake levers and commands be tight, or should they be able to twist, so that in the event of a crash, they do not break?

It depends.

On a road bike you'll want them fairly tight to be able to ride on the hoods without the brake levers turning away or moving downward on the bar.

On a mountain bike, at least the brake levers should be able to rotate away in case of a crash. But they still should be relatively tight such that they don't turn away while braking or because of bumps. Depending on where you ride, I'd rather have them a little too tight than lose the ability to brake because the levers are somewhere they're not supposed to be. As a rule of thumb, you shouldn't be able to rotate them without applying some force, similar to opening a pickle jar.


Can a bike have both Schrader and Presta tires? I have Kona Dew 2018 and the front tire has a Presta valve while the back tire has a Schrader valve. Is it common to see bikes have different valves for each tire?

Short answer, it's not common at all and probably wasn't like that when the bike was new.

The valve that you need is determined by the rim rather than the bike. If the rim is drilled out with a big enough hole for a schrader valve, then that's what you should use. If a schrader valve doesn't fit through the valve hole, then you should use a tube with presta valve. If one of the rims on the bike has been replaced (or drilled out), then they may no longer match and you would need one of each.

The more likely scenario is that at some point one of the tubes was replaced and instead of getting the correct schrader valve tube, a presta was used instead. This is easy to check as the presta valve will not fit snugly in the valve hole. If this is the case, it will work well enough in the short term, but I'd still recommend replacing it with the correct tube with a Schrader valve. Over time, the rubber around the thinner presta valve will rub against the edges of the larger diameter valve hole in the rim and eventually wear out.


What bicycle manufacturer used this emblem The top bar has the model name "AMERICANO" but I don't know the name of the frame manufacturer. I would appreciate your help identifying it.
Thank you

Your bike is a Scattante bicycle. They produce a model called the Americano and the logo can be seen in this photo of a different Scattante bike.


Does the superman style have any chance to be seen in competition? On social networks, many people have seen Michael Guerra's superman style.

Video here
The technique seems to be quite efficient, however it probably requires skills and yield to increase risks of falling. Also such technique is only worth it in long descents.
Is there any chance that such technique could be seen in high level competition such as the Tour de France for example?

I really doubt it. A number of problems pop into my head immediately.

Corners.
French/Italian/Spanish road surfaces.
Holding your legs up long enough to be worth it.
I'm pretty sure this video is staged.

Chris Froome caused a stir this year at the Tour just sitting on his top tube and that looked sketchy enough at 100kmh, twitchy and uncomfortable.


What racks will fit on a Pugsley? So I have a Surly Pugsley which I love dearly.  I want to add a rack to it so that I can do simple "grocery getter" tasks on my way to and from work, but I'm afraid that standard racks will not work because of the special nature of the frame.

Are there any racks out there that will work with a Pugsley?  Are there any modifications that need to be made for them to work?

I'll leave it to others to post a full answer, but I found this page about this very topic.


Shimano 11 speed component combinations I want to upgrade my bike to a 1x system using a Shimano GRX-crank upfront.

I however have a flatbar and can thus only fit flatbar shifters.

What is the lesser evil?

11-Speed XT derailleur with XT shifter and GRX crank
11-Speed GRX derailleur with XT shifter and GRX crank

Thank you in advance.

EDIT: I forgot to mention that everything including the rear wheel and cassette will be new.

I have found that Shimano offers non-series road flatbar shifters such as the 11-spd SL-RS700.

So this one can be used with GRX-derailleurs, as GRX is compatible to all roadbike components Shimano offers.

The original source (in German) is here : https://www.mtb-news.de/forum/t/shimano-grx-schaltwerk-flatbar-schalthebel.908787/


Independent ranking of bicycles aerodynamics Are there any scientific and independent evaluations of different bicycles from an aerodynamics perspective?

Aerodynamic testing is expensive, difficult and controversial. It's controversial because there are no real agreed on standardized methods for testing and what test setups replicate real world riding conditions.

Any research lab that does such tests are likely to sell the valuable data to manufacturers, rather than publishing it to the world for free.

Hambini (YouTuber, blogger and real-life aerodynamics engineer) did a comprehensive test of wheels and published the results on his blog, but I think he took them down. (Warning, if you watch his videos: he swears a lot and is very forthright in his very negative opinions of certain people and companies.)


What are the negative consequences of not bedding in disc brakes? It's common knowledge that disc brakes need to be bedded in. But I've never heard or found a description of what happens if you don't bed them in.

Given the number of BSO's that now have disc brakes, and the likelihood that 99% of those never get bedded in, I'm guessing that the consequences can't be too incredibly dire.

But what are those consequences? Reduced braking power? Uneven braking power? Squealing brakes? Reduced lifespan of pads and/or rotors? Are those consequences long term? Or do the brakes "naturally" bed in with regular use and the consequences are only short term?

I think your last comment is the operative point - it will happen anyway sooner or later.

The technology here is basically the same as with automobiles. You start off with new pads and a clean rotor. The bedding in process involves the deposit a small layer of pad onto the rotor (mixed in with a little frictional heat).

Until you have that layer on the rotor, braking could be less powerful and uneven.

You don't ask this, but for completeness, the rotor should be cleaned whenever the pads are changed, using isopropyl alcohol. And, once the rotor is clean, the bedding-in process will start over.

You don't see an awful lot on this subject if you look on the web at bike pages, but as I say if you start looking in the context of cars, there's lots out there and it is definitely not new technology.


Explanation on the lineup of Shimano Derailleurs I am pretty sure that almost everyone in this community knows the answer to this question but not me. I found this picture on the internet.

I am just a beginner and I still don't understand the difference between Altus and Acera, TX and TZ, where is Tiagra, Claris, Dura-Ace, and other major types of derailleur in this list. I somehow find the SRAM lineup to be clean and easy to understand but Shimano is a total mess for me. Can someone please explain the complete hierarchy of Shimano derailleurs? Am I the only one who messes this up? Thank you!

refer here:
https://productinfo.shimano.com/download/pdf/spec/3.1/en
Mostly this is MARKETING.
Shimano tend to use the same designs for a lot of their products, but typically these are introduced earlier on higher groupsets and are 'trickled down' to lower ones.
Also your picture is quite old and SRAM have since complicated it considerably with its 'Eagle' groupsets.
If you refer here https://si.shimano.com/
then you can look at the actual diagrams for each derailleur
Referring to my first link, the current 'XTR' consists of three derailleurs:

M9100-GS
M9100-SGS
M9120-SGS

then Deore XT is:

M8100-SGS
M8120-SGS

SLX is:

M7100-SGS
M7100-SGS

Deore is:

M6100-SGS
M5100-SGS
M5120-SGS
M4120-SGS

This is the exploded diagram for M9100-GS/SGS
https://si.shimano.com/api/publish/storage/pdf/en/ev/RD-M9100/EV-RD-M9100-4387D.pdf
GS means long cage, and SGS means super long cage
The parts differ in the jockey wheel cage, which is two pieces of metal or carbon fibre enclosing the two jockey wheels
The outer cage is here
https://www.sjscycles.co.uk/gear-spares/shimano-xtr-rdm9100-outer-plate-assembly-sgs-type-y3fa98080/ for SGS
https://www.sjscycles.co.uk/gear-spares/shimano-xtr-rdm9100-outer-plate-assembly-sgs-type-y3fa98070/ for GS
both parts are VERY expensive because if you refer to my first link they are both made from carbon fibre. The SGS is 90mm cage (wheel axle to wheel axle) while GS is 74mm
The spec shows that this is 237g vs 240g, which you might think is nothing and indeed it is, but the spec also notes that the GS is designed for Shimano's 10-45t cassette, and SGS for the 10-51 cassette. Because of the extreme size of modern MTB cassettes, and Shimano's Shadow design (where there is only one sprung pivot, not two), a derailleur that works well with a certain large cog size might not work so well for a smaller cog.
So we can see if we look elsewhere CS-M9100-12 is 357g for the 10-45t and 367g for the 10-51t. Again, this is not a big difference, but if you are a strong athlete and do not need the low cog, then it makes no sense to have it, because with the smaller cassette range you get 28-32-36-40-45 cogs, which are BETTER than 28-33-39-45-51, in that smaller steps mean you can more likely pedal at your best cadence. If you are not a strong athlete that doesn't matter so much, and you'd be grateful for the extra 51t gear on hard climbs.
So the XTR (XT Race) has a philosophy of offering a small adjustment to suit the specific preferences of elite athletes.
The other XTR RD is
https://si.shimano.com/api/publish/storage/pdf/en/ev/RD-M9120/EV-RD-M9120-4388D.pdf
If one looks down to Deore XT, then  M8120 is THE SAME DESIGN as M9120, and M8100-SGS the same design as M9100-SGS
But, the lower knuckle on the XT ('plate body') is GFRP and the one on the XTR is CFRP. The latter is a very high quality material, the former not so much.
The outer cage plate on the XT is aluminium, rather than CFRP:
https://www.sjscycles.co.uk/gear-spares/shimano-deore-xt-rdm8100-outer-plate-assembly-sgs-type-y3fw98080/
and it's 7g heavier as a result (the inner plate is the same)
The XTR uses higher quality lighter fittings, such as this one:

at 10g
whereas the XT is 18g

The jockey wheels on the XTR are 20g vs 26g
https://www.sjscycles.co.uk/gear-spares/shimano-xtr-rdm9100-tension-guide-pulley-set-y3fa98090/
https://www.sjscycles.co.uk/gear-spares/shimano-deore-xt-rdm8100-tension-guide-pulley-set-y3fw98010/
And so on.
This results in the XTR being 44g lighter. So it's slightly lighter, slightly higher quality, and far more expensive.
If you look at SLX, then comparing the table it's almost identical to XT. But the outer cage plate is 66g rather than 35g, as it's made of steel
https://www.sjscycles.co.uk/gear-spares/shimano-slx-rdm7100-outer-plate-assembly-sgs-type-y3fy98050
In addition, SLX (and its road equivalent 105) uses relatively cheap jockey wheels without sealed bearings. An athlete could expect to give up 1W (out of 300W) because of this.
So the SLX and XT derailleurs are all but identical, except for the jockey wheels and a cage plate, and if you had purchased a bike with SLX derailleur then you could very sensibly replace the jockey wheels (which are also more durable). Possibly the cage plate too, although it might be a different colour!
Looking at the M6100 then it appears to be almost identical to the SLX
https://si.shimano.com/api/publish/storage/pdf/en/ev/RD-M6100/EV-RD-M6100-4677.pdf
except there is a slightly different bracket axle, and the inner cage plate is steel rather than aluminium. This adds up to 10g.
Again, you could effectively upgrade your M6100 derailleur to XT level by replacing the jockey wheels, and maybe the cage plates (though this latter is not so crucial, though lighter weight hanging off your wheel can't be a bad thing).
For 2020-1 Shimano have split 'Deore' into three levels:

12-speed
11-speed
10-speed

The latter of these would previously have been known as Alivio, but due to people sharing inaccurate diagrams like  yours they decided to call it 'Deore', as it allows them to sell a lower quality groupset a higher price and most people won't notice.
We can see this if we refer to the M4120 derailleur in the specification table, where we see no 'GFRP', and lots of 'resin', which means 'cheap plastic'. Shimano may use different kinds of 'resin', but it's a sign you have a relatively cheaper derailleur.
If we look at M5100 and the diagram https://si.shimano.com/api/publish/storage/pdf/en/ev/RD-M5100/EV-RD-M5100-4675.pdf
then it turns out it's based on the M8100/M7100/M6100 derailleur
https://si.shimano.com/api/publish/storage/pdf/en/ev/RD-M6100/EV-RD-M6100-4677.pdf
however the spec notes it's '11' rather than '12' speed. The 11-speed jockey wheels have a different part number, so are likely subtly different.
The M5120 and M4120 derailleurs appear to use similar construction, but M5120 has 'Shadow+', which means it has a clutch, whereas M4120 does not. The clutch mechanism is in fact identical across XTR, XT, SLX, Deore.
Looking beyond Deore, scrolling down we find M3100 Alivio, which is in fact (looking at older spec sheets) based on M3000 Acera, so Shimano have reduced the quality of Alivio to Acera level.
Of course there wasn't much difference before. Comparing M3100 Alivio (which would previously have been called Acera) with the M2000 Altus, then the specs show only very minor differences, and it would be hard to call the Alivio a meaningful upgrade on the Altus.
The other difference with Alivio/Acera/Altus/Tourney is they are a different design intended for older drivetrains which used a triple or double front chainset, and a smallish cassette sized 11-36 or 11-34. This is very different from the current Deore-XTR, which use large 10-45 or 10-51 cassettes, which require a different derailleur design.
The distinction specifically with Tourney is that it doesn't follow the 'Shadow' design, which means it uses Shimano's older design, from more than 20 years ago.
The TX800 appears based on RD-M280 from 2012 https://si.shimano.com/api/publish/storage/pdf/en/ev/RD-TX800/EV-RD-TX800-3745.pdf which in turn will be based on much earlier derailleurs.
So there is not necessarily a big quality difference with Tourney, but Shimano don't really guarantee that - for example, a Tourney shifter might use lots of plastic internally whereas Altus might be more metal. It's more that Tourney is outside the groupset hierarchy and is not promoted or marketed - it's their intention to push people toward more profitable parts.
Note also that Tourney parts are typically made in Shimano's Indonesia factory, whereas higher grade parts are made in Malaysia, and the newest parts in Japan. A lot of people prefer 'Japan'.
As far as Di2 goes, Shimano haven't bothered with it for the latest series of parts. Maybe they will in the future. It's an electronic gear shifter for XTR and XT, which adds a motor to the derailleur.  SRAM do have a slightly more advanced version of this called 'AXS', which is wireless.
Actual racers might not use even 'XT', if they aren't sponsored - for example, for brakes SLX and XT turn out to be almost identical, so you might find a bike with XT derailleur and SLX brakes.
As far as Saint goes, it's arguably Shimano's highest quality kit, but it came out in 2012, and uses 10 speeds, not 11 or 12. It's for downhill racing, which means it's strong as a priority, and won't work with a large gear range. It doesn't use any plastic except for the clutch mechanism, and the design is related to circa 2012 XT, and has little to do with modern stuff. Zee is the cheaper version of Saint, so some steel parts in place of aluminium, and SLX/Deore quality jockey wheels rather than the XT-grade sealed bearings on the Saint.
So you can't make too many generalisations, but generally XT is always high quality, XTR is for people who are sponsored or have lots of money, Deore and SLX for drivetrain purposes tend to be very similar, Alivio, Acera and Altus tend to be similar to each other and lower quality than Deore/SLX (but you can't just go by name, as the model number differs), while Tourney might be lower grade, but will lack anything vaguely recent in terms of design. Note also that Tourney has a bunch of different model numbers.
As far as SRAM goes, I don't care too much about them, but they have 'AXS' electronic wireless shifting, and then they have their 'Eagle' brand which refers to 12-speeds, which they got before Shimano. Initially this was very expensive, but now they have released several grades:

XX1 Eagle (Axs)
X01 Eagle (Axs)
GX Eagle
NX Eagle
SX Eagle

and are promoting these. This is quite confusing, as as your diagram shows they used to have the top 3 but not the bottom 2.
I have seen more than a dozen reports of broken SX Eagle derailleurs snapping at the top knuckle, due to use of poor quality plastic, so it's not clear where the quality level comes at all, as because on the one hand they want to promote 'Eagle' = good, but on the other hand the SX Eagle probably comes around Shimano's Alivio level (which is 9 speed vs SRAM's 12) in terms of quality of construction.
So don't believe for a moment that SRAM is less confusing, or that you can rely on brand names. In fact an older 'Deore' derailleur' might be higher quality than a newer SLX one. So....


Can the length of disc brake hose influence braking power? I recently installed new brakes (Shimano SLX 675), shortened hoses for front/rear brake, done bleeding but even after that rear brake lever feels much softer than front. (I had identical issue with old brakes (M446) which acted in the same way and that is partially the reason for asking this question).

New brakes work fine, they have nice stopping power, there are no signs of oil leaking etc... It is just that rear brake lever feels much softer (and I don't think it is due to lever reach adjustment; it isn't nearly reaching handlebar).

Can the longer length of disc brake hose (rear breake) influence the 'feel' while braking (assuming brakes are correctly installed and working properly) or there is something else causing this 'problem'?

This sounds like an incomplete bleed. If you hang your bike vertically, try pulling the rear brake lever after it has sat overnight (front wheel up). if it feels extra bad that confirms it. Or if you notice that the brake feels better after a few 'pumps'.

That said, I had noticed with my SLX brakes that the front and rear had a different 'feel' possibly. Not that they acted differently at all, but felt different through the stroke of the lever. I thought it was possible it was the factory bleed, which wouldn't be the case for you, but perhaps there is something to it. Or possibly a difference in friction in the Pistons in the caliper or lever somehow.

On my Jamis dragon actually (separate M675 from above), I think the front brake ended up with too much oil from the factory bleed on the front. I couldn't get the pads open enough to not rub the disc. I put a bleed block in the caliper and opened the bleed screw on the lever and that pressure alone pushed a bunch of oil out. I closed it up and everything worked as it should have. Possibly something similar has happened in your case, but too little oil? (this could happen if the Pistons were too far retracted in caliper/lever not fully open during bleed)

side notes: Of course the front lever is going to provide more stopping power as it has greater mechanical advantage. Also some bikes have a larger front rotor. And never rule out quality control.


What are criteria for a team to get UCI World Tour license for the next season? I do not know much about this question, the only thing I have heard is that commentator on Eurosport mentioned a few times that UCI points one rider obtains are counted for the team which signed him for the next seasons.

So I wondered what are the criteria based on which a team gets WT license for the next season? Is there some minimal number of points they must have? Are there some conditions about the budget? Are there some other conditions a team must fulfill?

After andy256's comment I have looked into UCI cycling regulations. To prevent link rot, I am also adding link to the Wayback Machine. (And even if this fails, it should not be that difficult to find the file on internet.)

It is mentioned there that licenses are awarded based on sporting, ethical, financial and administrative criteria.

Top 16 teams in the UCI World Tour team ranking automatically satisfy the sporting criteria. (2.15.011a) Two more teams are added based on the UCI points from their five best-placed riders in the individual ranking. The teams have a choice whether the riders from the season just complete or the riders contracted for the following seasons should be considered for this purpose. (2.15.011b)


Odd screw on brake disc Worked on my first disc brake bike yesterday.  It was a full-suspension BSO with cable disc brakes.

The rear wheel had two broken spokes, and they where threaded such that I could not replace the spokes without removing the disc (and the cluster).  When it came time to remove the disc, five of the screws holding it were standard Allen head screws, but the sixth was a "Torx" style splined head (which required a run out to Home Depot to fetch a set of Torx bits).  The screws were all same diameter, length, and thread.

Was there any reason for this one odd screw?  I saw no evidence that the disk had been removed previously.

Many of the smaller bolt heads on MTB components tend to be Torx these days, especially for certain brands. For example, of the components I own, the SRAM mtb derailleurs, brake levers, brake rotors, shifters, etc use Torx-headed bolts, yet all the SRAM road components I own are strictly hex keyed. Why they don't stick to one style- preferably Torx- I don't know. I do know that Torx provides more "bite" which results in a bolt head that is less likely to strip, especially in smaller sizes. This makes a lot of sense, especially where higher torque is required such as brake rotor bolts which typically require a higher torque specification in comparison to similarly sized hardware.

That said, there would be no real technical or performance reason to have only one Torx bolt per rotor. I know that many cars with alloy wheels use a single lug nut with a special head per wheel and normal lug nuts on all the rest of the bolts for theft protection. Perhaps this is supposed to be something analogous to that. Alternatively, since you stated that this was a BSO (or Bike-Shaped Object, usually referring to a low quality or department store bike), it's possible that a) a single Torx bolt is used to discourage low skilled workers that are assembling the bikes from removing the rotors, especially if they are of differing sizes, or b) this is simply what they had laying around and the single count on each rotor is a coincidence.

Bottom line, you would not find this as a "feature" of disc brakes or bikes equipped with them of any real quality.


Converting a 7/8spd cassette to 4/5spd Lets get some things ticked off:

Friction shifting, check
Narrow stance cranks, check
2 or 3 spacers on the right hand side, check
Single chainring, check

(That's the context.)

Are there cassettes which can be disassembled completely and reordered?
If so, what type/what manufacturer/what time period/what product line?
If you take out cogs 6, 5, 3 from a 7spd cassette, is there a derailer capable of handling that range?

... Anything I haven't thought of?

edit: I just thought of something else... The spacers may not be such an easy part to get hold of. The spacing is all completely different. Would 4 7spd cogs + 3 of what might be called '7 to 8spd' spacers all fit together nicely on a 7spd freehub? This is what I'm not sure of.

Because you can does not mean you should, however as an experiment, if it does not work you can always put the cassette back together as it was in the factory.

Most Shimano cassettes that don't use spiders can be disassembled (usually cheaper ones). They are held together by either rivets or small screws with hex head. You can drill out the riveted one easily enough - these are no needed once the cassette is installed.

With the right spacers, it would be possible to custom make a cassette with 3 or 4 cogs and any sizes you have availble (Do make sure the cogs a placed in ascending order, although ). The shifting won't work smoothly, as the ramps and stuff on the cogs will be in the wrong places.

Refer Sheldon Brown - section "Building Custom Cassettes"


Is Ultegra 6800 GS compatible with an HG800 11 speed 11-34 cassette? I'm running Ultegra 6800 with

a 52-34 chainring up front (not a typo: I replaced the 36 with a 34), and
a 6800 GS (medium cage) derailleur at the back, and
a 12-29 rear cassette.

It works well.

My question is this: could I drop in an HG800 11-34 cassette?

I am aware that this would exceed the max total capacity (41t instead of 37t) and also the maximum sprocket (34t instead of 32t), as per Shimano's documentation here:
http://bike.shimano.com/content/sac-bike/en/home/components11/road/ultegra1/rd-6800-gs.html
But I'm already exceeding the maximum front difference (18t from 52 to 34, instead of the claimed maximum of 16t) --- with no ill effects.

Shimano is notoriously conservative.  Does anybody know if it would actually work?

In summary: would a set-up with 52-34 up front, 11-34 at the back, work with a medium cage Ultegra 6800 derailleur?

Thank you.

As for clearing a 34, there is no universal answer because it's slightly dependent on where the dropout puts the RD mounting bolt relative to the axle center, which despite Shimano having a standard spec for does have some variance bike to bike. So it's a little bit of an experiment every time. Generally speaking this can be made to work on RDs, including the one in question, with a max cog spec of 32t by running the B-tension screw in reverse or subbing in a longer one. It's also common for it to barely work and/or be a little grindier than desirable in the low gear but basically work. And remember that when you do this, something is lost in shifting performance on the rest of the cassette, so it's not all upside.

Exceeding the printed large cog spec by two whole teeth without any B-tension hacks usually doesn't work. I've tried it with various of the 11-speed road RDs, probably including this one but I can't be sure.

As for exceeding the total capacity, there are many answers here on this topic but basically the bike will be rideable but will have chain slack in some number of the small/small combinations. Total capacity numbers can basically be taken at face value (in other words they're reasonably honest), so you can do the math to see which ones will be slack, again with a very slight bit of wiggle room due to variance in dropout geometry. Here 18t of the total capacity is being used up front, leaving 19t in back. 34-19=15, so once the chain is long enough to wrap around the 52t ring, 34t cog combo, it can be tensioned on a 15t or above, and below that it will be sagging/floppy. Riding in the floppy gears carries some risk of derailment/jamming.


Incrediably stiff rear downshifts I have a '13 Trek MT-60 for my son that uses a Shimano Tourney derauilleur with a 6 speed revo shifter.  The problem he had was that the shifting with it was incrediably stiff, even for an adult.  I figured it was the shifter and I replaced it with a 7 speed SRAM Gripshift Max that I pulled from my bike.  It was a really easy shift for me so I figured it would be an improvement for him.  However, the downshifting is still really stiff.  Now I'm wondering if I need to look at the derailleur itself.  Other than coating it in lube and hoping it works, is there anyway to adjust the spring tension on it?  Would going to trigger shifters like basic Shimano EF-51 work for a young kid?  He has a Islabike as well and has no issues working the SRAM grip shifter on it.

It's probably the gear cable. Over time, grease and dirt get trapped inside the plastic housing. I would recommend replacing both the inner and outer parts of the gear cable (note they are not the same as brake cables). You'll need an end cap and ferrules as well


cogs for front wheel See this wheel. Can I put two freewheel cogs on it, instead of one freewheel and one fixed? (driving clock and anti clock, so both driving forward)
Then get this wheel onto front steel fork, by bending open a bit?
I haven't fully worked out the driving thing yet, so can't explain it.
Thanks

If you really need a freewheel on each side, that both drive the wheel forward, then you would need a custom built hub with a left hand freewheel thread on the left hand side, and you'd need to build a left hand freewheel too.

If you just needed a freewheel on the right hand side, just use a single speed bike rear hub.

You would of course need a custom fork for either as rear hubs are wider that front hubs.


How fast can a cyclist accelerate from a standing start? I'm less interested in the empirical answer to this question and more interested in the theoretical physical dynamics that govern this.
I understand that the rider applies some force to the pedals (which could also be thought of as a torque given the length of the crank arm),but the answer isn't simply F=ma because there are gearing ratios involved. In short, I'd like to know the process of calculations by which one could approach this problem and determine the maximum acceleration of a rider.
I suspect some assumptions will be necessary:

Max force applied to pedals = rider weight (this is probably not quite correct if using clipless pedals but probably fairly close?)
Optimal gearing ratio is available
Let's assume a relatively instantaneous problem regime, i.e. a 2-second standing start or something like that

If more information or assumptions are needed, please advise. I'm also open to migrating this to say SE physics if that's a more appropriate place for it.

The power-drag equation is well-understood if not widely-known, and is discussed in this bicycles.SE answer. In particular, the drag equation shows the component for changes in kinetic energy, viz., acceleration. You're asking about a standing start, so initial speed is low and we can ignore the aerodynamic drag component. In addition, let's assume the rider and bicycle is on a flat surface, so we can also ignore the potential energy component. Finally, although there is a rolling and mechanical resistance component to drag, it is typically small so let's ignore it here.
What's left is the kinetic energy component. F = m a is the correct equation to use, but you have to convert F at the pedal to F available at the rear wheel. Then a = F / m. There are a series of lever arms between the pedal and the point at which the rear wheel touches the ground involving the length of the crank arm, the gear ratio, and the radius of the rear wheel. Let's say the total lever arm "gain ratio" is c. Then F Newtons of force at the pedal translate to F / c Newtons at the rear wheel. If the total mass of bike and rider is m, then the acceleration of the bike and rider is F / (m * c). Martin et al. (2006) uses this technique to model sprint performance, with very good results.
Maximum pedal force can actually be greater than body weight, if you can hold onto the handlebars. In fact, maximum pedal force approaches 1RM ("1 rep max") force from a leg press. A world-class track sprinter has a 1RM of roughly 4x body mass; more commonly, most of us can produce pedal forces equivalent to at least twice body mass. So, depending on the gain ratio calculated above, maximum acceleration is likely to be somewhere in the ballpark of 0.2g to 0.4g, or between roughly 2 and 4 m/s^2.


Will 11 speed 55-42T Shimano Dura-Ace 9000 crankset will be compatible with an 8 speed 11-28T cassette and shifter? Will a Shimano Dura-Ace 9000 55-42T crankset be compatible with my current Shimano 8 speed 11-28T cassette?

The purpose of this change is for Time Trialling.

Nominally no, an 11 speed speed crank will not work with an 8 speed drivetrain.

As the number of speeds (number of cassette sprockets) increased as new groupsets were released, the sprockets were narrowed and moved closer together. The outside width of the chain was also progressively narrowed so that they worked with the narrower sprocket spacing. This also meant that crank chainrings had to be moved closer together. An 8 speed front derailleur and chain will not shift at all well on a 11 speed crank.

Other things you should bear in mind if you are serious about a 55/42 crank. You may not have enough chainstay clearance for the bigger rings, and you will need to check that your front derailleur will move up enough - some braze-on clamps don't have enough adjustment.


Techniques for minimising injury when falling or crashing? I've been riding bikes since I was a child but my partner only started when she was in her 20's. She's had one fall where she lost teeth and is keen to avoid future injuries. I've broken bones twice and had innumerable grazes and scrapes but the frequency of those has been dropping for a while.

We live in Melbourne, no snow in the winter but 45 degree days in the summer are becoming more common (115F). We both commute and generally ride for transport, mostly in urban/suburban streets and bike paths but very rarely on busy multilane roads. Mostly at 20-25kph (25-25kph for me, but it's mostly her I'm concerned with).

My problem is that I've got enough wrestling experience that I automatically bounce, roll and run when I come off my bike. Saying "just study aikido for a few years" is not really what she wants to hear, but we expect she will need to train or practice something. Ideally something specific to cycling rather than just suggesting something like aikido.

She has gloves and wears them sometimes. I almost always wear gloves while riding. So other suggestions for protective clothing etc would also be handy.

I'd like suggestions as to what she can do to minimise future injuries. This is not "how to avoid crashes" but "what to do when you crash".

In my experience dealing with crashes and bounces is like a lot of other aspects of, especially urban, cycling in that anticipation and prediction are the key attributes to getting away with less damage.

After all, if you don't crash, you won't damage yourself (whether you're lidded or not). It's a variant on Gary Player's infamous quote, "The more I practice, the luckier I get" - the more you think about what could happen, rather than just letting the world happen to you, you'll be better at predicting dangers and avoiding them: speed into corners, visibility around bends, road surfaces, car doors, cars appearing at junctions, and so on.

Learn to look a little further ahead - that red light 50 metres in front? React to it when you're 100 metres away (and more importantly, consider what others might do). My last crash was when I cycled into the back of a delivery van while looking over my shoulder to see if it was clear to move to the outside of the lane - while I was looking round, the van was slowing for some traffic lights I hadn't considered, so I piled into the back of him unawares.

I know that this isn't a "what to do when you crash", but I think that there is more to crash preparation as a part urban cycling than how to fall. Cycling has a mostly undeserved reputation as being a dangerous pastime. Most accidents I hear about (definitely the handful I've had in the last few years) have been utterly avoidable and not actually that accidental.