Approximately where is the center of mass of a mountain bike? Take a "standard" multipurpose bike like this one: http://www.islabikes.co.uk/bike_pages/beinn29.html (Weighing 12.2kg)

I'm conducting a physics investigation, and for this I need to know the approximate location of the center of mass of the bike, or any similar bike for that matter. (Are there any sources for this?)

Now, before you holler at me about it being impossible to determine, too many factors etc, I just need an approximate value, precision isn't too important.

Thanks!

Assuming you want the center of gravity of the bike alone (not with a rider), there is a very simple procedure you can perform yourself, as long as you have some bike (you could borrow one):

For simplicity, strap the front wheel to the down tube of the bike, so the handlebars won't turn; You could also strap the brake levers in the "full braking" position;
Lift the front wheel from the ground, balancing the bike on the back wheel. Lift as much as necessary so the bike keeps almost falling back. Now the vertical line passing through the rear hub is the line where the center of gravity is;
Repeat the procedure with the rear wheel lifted, so that you know the the center of gravity is directly above the front hub;
The approximate center of gravity position is where both lines cross.


Freehub vs freewheel in a singlespeed? I'd like to know what is better in terms of maintenance and reliability in the long term.

I currently have a flip flop hub with a freewheel which I had to replace recently. For what I saw there were not many options in the market and they where quite expensive (white industries around 100€, halo clickster around 50€ and some other cheaper options which I don't trust anymore).

Depending on which one you buy, I've read they last around 2000-6000km (the cheap one I had was under 2000km...).

I'll replace my wheels in the future and probably I will have a custom build so I can choose the hubs.

The track hub for example, in shimano dura ace  is around half the price of the freehub. The hb900 costs around 240€ and a campagnolo super record pista or dura ace 7710 around 120€.

Is it worth it to buy the freehub or are there other things to take into account? Will the freehub fit in a bike that had a freewheel hub?

For maintenance and reliability, you can probably rank them in approximate order of the White freewheels being best at everything, then the premium singlespeed cassette hubs (King, Profile), then after that I'd put the nicer BMX freewheels, then the nicer generic-brand singlespeed cassette hubs (Novatec), then the junkier singlespeed cassette hubs, then the cheap BMX freewheels. It's all opinion based but that's my experience being around all that stuff.

Note that rate of engagement is a major distinguishing factor between the options (kind of the major one as far as a lot of riders are concerned), but it doesn't really follow the above order because there are some pretty nice freewheels in terms of construction with pretty bad ROE, and likewise there are any number of junky, gimmicky freewheels and cassette hubs with high ROE and bad durability.

Generally speaking, non-BMX singlespeed cassette hubs come in 130mm or 135mm, not the "trackier" 120mm, and won't be able to be respaced to 120mm because if it's well-designed then its flange-to-flange spacing will preclude that. There are BMX race cassette hubs that can be respaced up to 120 (from 110), and I'm under the impression that the Profile 120mm cassette hubs, which is the main off the shelf one that exists, are essentially a manufacturer-provided version of such a hack, but there's downside there that because the flange-to-flange was designed around a 110mm hub, you're sort of giving up strength for no reason if you space the hub 120.

I'm just going to flagrantly disregard SE rules here because the really good products in this category don't change much over time, and say that if you really want durability and reliability here you should take your pick between White, Profile, and King and call it good.


Will brand matter between a rear derailleur and front derailleur? I had a crash recently that destroyed my 8 speed sensah reflex rd. I replaced it with a 9 speed shimano sora for a bit of upgrade but after 4 tune ups by the mechanic its still not right. Just so discouraged pls help. I noticed also that my rd hanger is kind of a little bent or not straight enough will this matter? Thank so much in advance...

I believe you are referring to the shifter, not the front derailleur. The shifter connects to the derailleur with a cable
Sensah Reflex is an 8 speed system with components designed to be interchangeable with Shimano 8 /9 speed.
http://www.disraeligears.co.uk/Site/Sensah_Bicycle_Components_2020_page_6.html
Probably the Sora RD is slightly better quality, not because it is 9 speed but generally Shimano have better manufacturing standards and shifting quality than most other brands, though Sensah doesn't seem to be terrible at all.
There is no difference between an 8 speed and a 9 speed RD so that part is fine. (Often a 9 speed is a more expensive part and made from lighter materials , but that's all)
Given that you still have shifting problems and have identified that the derailleur hanger is bent, it is obvious that that is the source of your problem. So find a replacement derailleur hanger, keep your Sora RD. If you can't find a replacement hanger perhaps you can straighten it, but given your mechanic has failed to do so replacement seems a better option.
https://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment


Shimano Sora FC-3503 chainrings I want to change my 50T chainring of my Shimano Sora FC-3503 crankset.

Do I have to buy the same one or other chainrings are also compatible with it?

If yes could you give me some light which ones ?

Thanks in advance.

The 50 tooth chainring is a standard 5 bolt, 130 BCD chainring. There are other options available that will fit, but most 130 BCD will have 53 teeth, so you may have to hunt around for a bit to find a 50 tooth that you like.


What should I do about a tensioned/trued wheel that lost significant spoke tension after first use? My front and rear wheels needed truing, so I picked up tools to do it.  Rims are DT Swiss R460: 20 spokes front, 24 back.  Max spoke tension is 1200N.
I got my front wheel to a left-side tension range of 685-889N and a right-side tension range of 685-938N, and I got my rear wheel to a left-side tension range of 540-720N and a right-side tension range of 758-991N.  Numbers are without tire or tube and after de-stressing both sides of each wheel.  I adjusted each spoke using tighten-then-back-off spoke wrench technique.  I didn't use spoke prep -- figuring it wasn't strictly necessary for an existing wheel if I was attentive and executed tighten-then-back-off correctly.
I put tires and tubes on the wheels and reinstalled them, then did 13mi Sunday.  The rear wheel felt maybe more "taut" than normal (from fresh reinflation to max 120psi?), but otherwise things went fine.
It's now Tuesday, and I figured it'd be a good idea to recheck tensions after a ride and some time.  Didn't remove the tires, just popped the bike in a stand and ran the TM-1 over a few spokes.  The tensions were much lower, 14-16 on a TM-1 versus 17-22 before for a few random left-side spokes on each wheel.  (Maybe "taut" is not actually what I was feeling in the rear wheel.)  That decrease isn't normal -- is it?
Should I just tighten all the spokes to get them to a more desirable tension range again?  Is it normal for tension to decrease so much from putting an inflated tire on a wheel?  (This answer suggests no.)  Should I remove (or at least deflate) the tires before doing so, and if so should I tension beyond 1200N assuming some loosening when a tire is added again?  (This answer again suggests no.)  Or is my no-spoke-prep tactic coming back to bite me, prior tensioning would likely have been fine if I'd used some, and I should apply some to every spoke and then tension things up?

Yes, it’s normal for spoke tension to decrease when the tire is inflated.
First of all I’d use much more tension and try to get it more even. Currently you have about 30% difference between slackest and tautest spoke, which is a lot (I’d aim for ~10%, but I’m a perfectionist in that regard).
540N on the slackest rear spoke before you’ve even inflated the tire is very little. I’d get the drive side spokes to slightly over the allowed 1200N and hope that the non-drive side ends up around 700N.
I’d also aim for 900N on the front wheel.
All tensions assuming zero tire pressure.
Considering the low spoke count and the high tire pressure you are using you could go for even higher (initial) spoke tension.
I’ve had good experience with using grease on the spoke nipples (on contact surfaces and thread). Makes truing much easier, avoids wear from truing and also avoids deforming the spokes or nipples from all the tension force.


Does rear-shock placement affect suspension characteristics? I know that suspension type(Horst-link, Four-bar etc.) affects how a full-suspension mountain bike handles, but you can often see these same types of suspension systems used with different shock placement. Some have a shock that sits under the top tube, while others have the shock mounted at the bottom of the seat tube. Does this placement affect the suspension characteristics as well, or is the shock just placed where it is for convenience? And if it does affect the suspension, what kind of characteristics does the different placements give? As you can see on the pictures, both bikes have a Horst-link, but the shock placement is different.

Yeah, the main issue is the geometry that determines the arc the wheel follows as it responds to upward force on the tire.  Subtle changes in pivot points can affect that significantly.

Beyond that the spring force and damping force that the shock applies at each point in the wheel arc is obviously also important.  And differences in shock placement are one way that a manufacturer would "tune" this.

There is also, of course, the physical stiffness and durability of the shock mounting scheme, and the simple fact that some schemes facilitate a good frame design better than others.  And of course "coolness" and novelty of appearance are major criteria for the frame builder.

One critical factor that isn't visible in those photos is the precise location of the pivot at the front of the chain stays.  That probably affects "bob" more than any other factor.


Should I worry about rain getting inside my frame? I commute to work every day and lock my bike on the street.

I have a nice saddle so I remove my seat post and take it into work with me.

This obviously leaves a hole open to the inside of the aluminium frame. Living in London it often rains. Should I worry about raining getting into the frame by this hole and doing damage? And if so what should I cover the hole with?

It depends on the frame material what effect the water inside the frame will have. A lot of frames have a small hole drilled at the bottom of the bottom bracket casing. If there is no hole there you can drill one yourself. I have done this on aluminium frames before and it is very easy. Use a 4mm drill bit and drill through till you cut into the bottom bracket void. There will be a gap internally between the frame casing and the actual bottom bracket. A hole this small in the centre of the bottom bracket casing will not affect the strength of the frame but will allow water to drain. I have found frames fill up with water even with the seat post in place if ridden in the wet, so putting a cork in the seat post hole probably won't make much difference.


Slow lever return after shortening brake line and bleeding I've just recently replaced the brakes on my MTB with a pair of Shimano XT hydraulics. The rear brake line was extremely long for my frame's routing, so I had to cut it and subsequently bleed the system. For the most part, everything seems to have gone well; the rear brake lever is now very firm and responsive, slightly more so than the front (which I did not shorten or bleed). However, I've noticed that the rear brake lever no longer returns instantaneously. If I had to guess, I'd say it takes around 0.2 seconds to return from the fully depressed position. By contrast, the front lever returns so quickly that it makes a slight "snap" sound when it hits its limit.

I replaced both the olive and needle insert when reinstalling the brake line. I noticed that both of these parts had a thick grease generously applied to them from the factory. I'm unsure if this is typical for Shimano brakes, though I've never seen pre-applied grease on the spares for Avid or Tektro brakes. I have a sneaking suspicion that this may be the culprit, but I'm not sure how to validate that without disassembling the brakes again and swapping in new connector spares.

This doesn't seem to affect the brake's function right now, since the pads don't noticeably drag against the rotor during the return interval. But it does concern me that I may have done something wrong while reinstalling the brake line, and that this might be a precursor to more serious problems in the future. Any ideas what I might have done wrong, or how to further troubleshoot this issue?

Some more details:

The instructions I followed for shortening my brake line are these: http://www.epicbleedsolutions.com/blog/shorten-shimano-hoses-without-bleeding/
Shortening the line introduced some air, so I followed the official Shimano bleed instructions here [PDF]: http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Bleeding_SI/SI_0037A/SI_0037A_002_EN_v1_m56577569830648123.PDF

There are three possible things that could be causing this:

Too little mineral oil remaining in the system, did you top up the brakes after shortening them?. This would create a vacuum in the system and would prevent the lever from returning fully. *--EDIT on reflection I think this is unlikely with a Shimano brake as after oil falls below a certain level air would enter the system and the lever wouldn't work.
A blockage caused by grease in the needle creating a slow vacuum.
A broken spring in the lever. There isn't enough negative pressure in the system to force the lever to return so this is aided by a spring in the lever which also creates suction at the piston. Did you check the brakes prior to shortening the hose? This is a known failure for Shimano brakes.

My trouble shooting would be:

Check mineral oil level
Check the needle for a blockage
Take it to a LBS for some professional help


Are flip saddle posts available When trying out the baby seat on my wife's e-bike, it was really easy to fit and remove because her saddle flips up to access the battery.  It's a real pain threading the baby seat over the top of my pannier(s) and under the saddle to fit it on my bike.

FWIW the baby seat is a hamax siesta, seat tube mounted, and slightly fiddly to fit even with rack but no panniers. I can't fit the seat then the panniers - there's no access to fasten the panniers.

So is there a flip-up seat post available to fit to a normal bike?  Google finds nothing relevant, only ancient forum threads.

Edit: Pics

Here it is flipped up:

And in riding position:

Detail of the mechanism:

As you can see the standard QR height adjustment is unaffected, and the saddle rails are typical.

I've found out a bit more - apparently there's quite a bit of extra weight (looks like it, plenty of steel in there) and older versions had a tendency to work loose around the hinge.

Answering for completeness:

Such saddles are available but only as spares for E-bikes, from the bike manufacturers.  They aren't necessarily compatible with a normal saddle as they use unusual mountings, and the saddle post diameter isn't specified (instead they list which bikes it's a spare for).

They're heavy and not necessarily designed for hard use.


Which bike lock should I choose? For a long time I was a happy owner of an Abus Catena chain lock. However, last night someone tried to steal my bike. Luckily, they either didn't have enough time, or the lock was too tough for them so they abandoned it after cutting through 0.5mm from two sides.

Now I am looking for a better, more secure and more deterrent-looking lock. These are my current options:

Abus Granit Plus 51: U lock, security rating 13/15, 13mm thinckness, 23cm height, costs 46€
Abus Bordo 6000: folding lock, security rating 10/15, 5mm thickness, 90cm length, costs 55€

With the first one, I like the better security. However U locks are sometimes pain in the ass to set, especially because I usually lock front wheel and frame to a stationary object. I am not sure if this is even possible with this U lock, as the distance from the inside of the rim to the inside of the frame is a little more than 20cm.

I like the folding lock, because it is more versatile. I can lock my bike to a variety of stationary objects, but it is less secure for sure. Also, it is a bit more expensive.

I will keep my old chain lock, as it is not damaged too much and change the outer skirt so that nobody knows it was damaged. I thing it should be OK as a secondary lock when I leave my bike overnight in a communal room.
Any ideas what could be a smart choice?

I have recently been in a neighborhood watch training. Bike theft was one of the topic.

They showed us a footage where they asked a skilled thief to break various locks, from low end dental floss (10 Euro worth) to high end sturdy looking one (60 Euro). The thief was able to take rid of all of them in a matter of about 30 seconds, with few difference between flimsy and sturdy ones.

Bottom line: the only way to safely lock your bike is make it an hassle to remove all the locks with respect to the other available targets.

Use redundant locks (they will require more time to be removed)
Lock your bike where other similar bikes are available (thieves go for the low hanging fruit, unless you park a carbon frame 5000 Euro bike among steel 100 Euro bikes)
Make it hard for the thief to be unnoticed while working around your locks (don't lock your bike in a dark and out of sight alley)


Shimano RT66 Rotors on Tektro Auriga I'm thinking of changing my original Tektro Polygon rotors to Shimano RT66 rotors. Both use 6 bolts and 160mm size. Is this will be fine with my Tektro Auriga brakes? And will changing the rotors cause significant difference?

You'll just have to make sure that the rotors match the type of brake pads you use. Shimano mark their rotors for 'resin pads only' and the like! –


Rear derailleur cage hits largest cog on cassette I got a new rear derailleur for my wife's bike after a stick turned the original one into a twisted mess of metal. The derailleur is a Shimano Acera, the cage is slightly longer than the original.

The rear cassette is a Shimano MegaRange with 7 cogs, the largest being 34T and quite a bit larger than 2nd.

When engaged on the second cog, the inner cage plate begins to rub on the largest cog. Getting into the largest cog isn't possible due to interference with the cage. I tightened down the B screw all the way, but there just isn't enough room.

The inner part of the cage on the original derailleur is a bit shorter than the upper jockey wheel. On the new one, the inner cage goes a bit beyond the jockey wheel.

Is there some adjust I'm missing or a different part I should have gotten? Worst case, could I cut the inner cage plate back a bit for clearance?

EDIT:

I found the tiny stamping on the old deraileur, its a RD-M340. The new on is a RD-M360. Both claim to handle a 34T rear.

With a little manual intervention, I can get the chain up on the top cog and it turns smoothly.

The old (dirty) deraileur:

The new one in low:

The new one hitting the gear:

The inner plate seems to be on upside down. Not sure why but if it's second hand, maybe someone dismantled it to clean it the put it back the wrong way round.

If you need to swap it around you just need to undo the screws holding the jockey wheels in and flip it, then reinstall them. Its a bit tricky with the chain tension, but if you can do it without removing the chain, all the better.

Maybe drop the chain off of the chainring at least, to loosen some of the chain tension.

Make sure you get the chain routed correctly around the little tab on the inner plate, which is about halfway between the jockey wheels.

Also check the jockey wheels go in the right place and spin the right way; thanks to Carel in the comments, “If there's a difference between the top one and the bottom one there should be an inscription and an arrow with the sense of rotation.”


Soundsystem for bicycle Before starting to build a soundsystem for my bicycle I would like to ask where I can be redirected or provided info for a) a ready-made solution, b) a set of clear instructions on how to make one.

My requirements are:

It has to fit somewhere on the frame or the rack (maybe pannier style) - a trolley is not an option as I do not have space to store it.
The battery has to last a minimum of 5 to 6 hrs
It has to be loud enough for a city Critical Mass ride (many cyclists circulating together)

Thanks in advance!

I have seen numerous people riding down the path with a sound system on their bicycle. Without exception they use the simplest and most portable solution: a bluetooth speaker. This meets all of the requirements of outdoor usage:

Self Contained
Waterproof
Long Battery Life
No wires to run
Lightweight and portable
Inexpensive

Tie it to your bike rack and pair it with your phone. I've done it myself once, but be warned, you will need a louder one outside (especially at a critical mass ride). So you may have to invest in one of the larger models.


Bike comes with frame integrated bolt seatpost clamp - can I cut it off and use QR? I've got a Marin Pine Mountain 1 2016 - it comes with a frame integrated bolt seatpost clamp. Is it possible to cut this off and use a QR seatpost clamp instead?

Bike :

Seat Clamp :

Yes it's possible to hacksaw the clamp bosses off and then file the seat tube round and smooth so that a quick release clamp would slip over it.

Before taking such drastic action - which will significant hurt the resale value of the bike if you care about that - perhaps try to find a QR lever and skewer that will work with the existing clamp bosses.


Pedals won’t complete a rotation When I get on my bike and pedal when the right hits the top I can’t pedal and it stays and it keeps happening when the right goes to the top it stops and I can’t keep pedaling how to fix and any thoughts

If the cranks are prevented from moving at the same place in their rotation, they are most likely catching something on the frame, rather than the problem being with the gears or chain.

Some basic troubleshooting you can do:

Hold the bike of the ground, slowly turn the cranks forward and backwards by hand, look to see what they might be catching on. Sometimes the front derailleur gets rotated around the seat tube and sticks out into the path of the right crank arm.
Spin the rear wheel forward to make sure there is no problem with it.
Pedal backwards slowly and examine the chain, make sure no links have come apart. The side plates can stick out and catch in the derailleurs.


Chain noise, fixed gear This is my first bike ever assembled, I’m a total newbie.

I’ve just finished to put chain/cog and did my first try of chain tensioning. All components are new, but still I don’t understand why there’s so much noise when I pedal.

I’ve just put some lube to chain hoping it helps

Do you think there’s too much chain tension?
It was noisy even when the chain was slack, hope I bought the right chain!

https://photos.app.goo.gl/nTpEiKzsCfduMnRo6

Looks a little tight. There should be +/- 0.5 inch vertical movement of the chain possible halfway between the sprockets.

Park tool has a great video on single speed chain replacement:

             (link starts the video at the tensioning segment.)

Readjust tension and see if it makes a difference. Also make sure the wheel is parallel to the frame.

1/8 in (3.2 mm) wide chains are typically used on bikes with a singlespeeds, but 3/32 in (2.4 mm) chains are used also. Compare the new and old chain width. If it's the same it's good. ('Width' here means the spacing between the inner plates.)

Did you replace the front and rear sprocket with the chain? Check the sprockets for wear, especially the rear one.


bike lane interuptions In a stretch of my commute I have a nice looking bike lane that unfortunately currently has a couple unusable spots. I'm going about 20mph which is around half traffic speed.

So far I have tried two strategies, both with less than ideal results.

As I approach an unusable patch I signal, merge and take the lane for some 10-20 meters depending on how the merge worked and return to the bike lane where it again meets my standards. But this has in some cases has apparently been unexpected by cars who express their surprise unhelpfully. The bike lane's faults may not be totally obvious to a driver. In other stretches without a bike lane taking a lane hasn't been an issue.

Or as I approach the trouble I skirt the edge of the lane. I hold a line maybe 30 meters before the spot just about on the painted line (there are three spots and one of them the line is not usable so I'm in the lane) This makes me pretty predictable in the trouble spot which I take as helping my chances of being hit since cars typically give me space. But means I have little or no option to maneuver if someone does choose to pass close, so far it hasn't come up.

I'm pretty sure the first option is correct, but doesn't seem to be as well received and I've felt safer in practice using the second.

The question is: Is there a way to make this work better?

You don't say where in the world you are, so it's not clear what the traffic regulations are. I'm in the UK, so I'll assume UK-like regulations – bicycles are allowed to use the vehicle lanes even when there's a cycle lane and bicycles are basically supposed to act like cars.

First, regardless of regulations, you've missed option 3, which is to slow down to a speed where the cycle lane is usable. You don't say exactly what the problems with the cycle lane are but, unless they're so dangerous that the highway authority needs to have fixed them yesterday, you should be able to slow down for them. By approaching what you know to be bad sections of the cycle lane at speed, you are severely limiting your options.

Second, you mention motorists being surprised when you enter their lane. In jurisdictions that I'm familiar with, signalling a turn means "I intend to manoeuvre when it is safe to do so." In particular, it does not mean "Please make space for me – I'm gonna turn!" If you are signalling, it would be nice for somebody to make space for you, but that is not an obligation and a car rapidly braking from its 40mph to your 20mph is asking to be rear-ended. If your lane change is causing surprise, it suggests that your manoeuvre wasn't safe and that you were using your signal as a request for space rather than a notification of intent. After all, if there had been enough space for you in that lane (i.e., a long enough gap in the traffic), motorists wouldn't have had to react to your presence at all.


Why did my tire explode? Been running a set of quite nice slicks at 120-140 PSI for a couple of months. Might have done 400-600 km on the bike in that time. Tonight the rear tire exploded while the bike was sitting in my entryway. It's split right along the seam, with a roughly 2 inch long gap. Very loud bang etc.

Before I go out and buy another $70 tire, I want to get an idea of what caused this. Some possibilities that I've thought of include:

Running the tire at 140 PSI. The tire is rated to that pressure, but maybe this is still too much?
Some brief stretches of gravel road (1-2km) I did on it last weekend. The bike seemed fine then however.
There is a central heating/cooling vent directly adjacent to where the bike is stored. Perhaps the changes in temperature were enough to damage the tire?
The roads in this area are not always very good. Maybe this is just the result of accumulated damage from dozens of minor nicks and bumps?
The tire could be defective.

Edit: added a picture. Looks like the tube has a ~1cm hole in it.

My guess is cords were damaged on the ride creating a weak spot. Threads held together long enough to get you home and a bit longer, then ripped apart. This kind of delayed and catastrophic failure is not uncommon. Heating vent might have softened them enough to make a difference, but the tire was damaged anyway (assuming warm, not very hot air).

More puncture resistant tires may help prevent it in the future, but you cannot prevent it completely.

The size of the hole in the tire, and the hole in the tube are irrelevant, its a symptom of the tire failure, not the cause. Once the tire fails, there is nothing stopping the air pressure inside the tube expanding - the tube cannot stop it, it gets pushed though the tire, making that hole bigger and blows up and pops just like a balloon, hence the bang. If you were listening closely, the bang was preceded by a short ripping sound.


replacing cassette & chainset I think the time has come to replace my rear cassette, it has begun skipping in a certain gear. I'd also like to give myself a bigger granny gear (something like a 28 or 30 would do). I haven't done much in the way of maintenance/buying new parts before so am after some advice.
Bike - Bianchi ML3 Alloy Reparto Corse.
The current cassette is a 9 speed.
Rear derailleur Shimano 105
Front derailleur Tiagra.
Chainset is 105 (looks like 53/39 which I think I'm happy with).
Shifters 105 brake-mounted.

So I guess chain will need changing as well, and possibly chainset (it has done a reasonable number of miles).
My question is - when I'm looking at cassettes I see there are a few 9 speed options, eg HG 50, PG 950/970 SRAM, Ultegra CS6500. I'm happy to pay a bit more for something decent. I guess what I have now is SRAM, but I don't know for sure! I very much doubt it's Ultegra. If I did go for the Ultegra would that mean I have to buy an Ultegra chainset too? And what about the derailleurs & shifters, would they need to be changed to Ultegra as well? I don't know what combinations 'just work'. And what about Dura Ace etc?
I am looking at 9 speed because I seem to remember someone saying to me that 9 speed is the most my frame will accommodate, I don't know whether that is right. I can't find any frame specs that tell me that information which is really annoying (maybe I'm looking in the wrong place).
Thanks for the help, apologies for the noob questions.
Guy

Generally speaking, a frame/wheel hub that is fitted with a 8/9/10 speed cassette can take any of 8/9/10 speed because they're all the same width, just pack an extra cog or two in by thinning down the chain and inter-cog spacing.
11 may be possible but it depends on how the cassette can overhang inboard of the freehub without grinding.  12/13/14 speed is right out, unless you're buying a new bike.
The reason for staying with 9 is that you don't need to change the shifter and possibly rear derailleur.  The cost of these parts adds up, so going to 10 speed gives you only one more cog but costs a lot more.   Minimal change from maximal expense.

You're right the chain absolutely needs changing.  The chainrings may be adequate as-is, but its wear-dependent.  Also check your derailleur's jockey wheels - there its sideways slop more than tooth wear.

Mostly all 9 speed stuff is interchangeable. At 10 speed the standards start diverging, with differences in MTB/road, and tiagra doing its own weird mixed up standard.
Personally I'd replace with a 9 speed chain and cassette, check for wear in jockey wheels and chainset, and then keep riding.     Shout yourself some new bartape too, and the bike will feel awesome.


Use of an alternative chain lubricant What is the best chain and gear lubricant used by pro cyclists either for maintenance or for racing and how often is it recommended to apply? I have limited knowledge and so I have always simply used a product named Castrol EP 90.

That Castrol EP 90 has a gear oil viscosity rating of SAE-90? That is way to viscous for use on bicycle chain. Dirt & road grime is going to stick to it like crazy, wear out the chain & cause a lot of friction.

You need to use a bicycle specific chain lube. Which one depends on your riding conditions.

There are generally "dry" lubes & "wet" lubes.

Dry lubes are usually a solvent carrying a wax based lubricant. The solvent evaporates after application, leaving the dry wax in place.

Wet lubes are oil based without a solvent that evaporates away, thus remaining wet.

In addition, wet and dry lubes, as their names imply are best suited to wet & dry conditions. Dry lubes do not attract as much dirt as wet lubes, but wash off quickly in wet conditions. Wet lubes hold up to water much better.

Depending on conditions, a chain should generally be wiped down / cleaned ~100 miles or so & re-lubricated.


Pannier for MacBook Pro 15 retina? I'm commuting with a backpack, and I don't like having the weight of my laptop on my back for the whole commute (30 minutes).

So I'm looking to buy a pannier that I can easily take off when I get to my destination, and use it as a bag, like a messager when I'm off the bike.

Do anyone know of a good one that would fit a MBP15 retina? Something like this would be great:
http://www.timbuk2.com/shift-laptop-pannier-bike-messenger-bag/439.html?dwvar_439_color=2001&dwvar_439_size=7

But not only it's sold out, it doesn't fit the MBP15 Retina.

I have the Timbuk2 Especial Viaje convertible backpack/pannier which I use to commute with my work laptop, a MBP 15" Retina. It uses the same rack-attachment hardware as the current edition of the Timbuk2 Shift. That hardware has broken 4 times in my ~8 months of owning the bag. Timbuk2 has been good about sending replacement hardware, but it's still not fun to have to maintain the bag that much, especially considering Timbuk2 sells their bags as being very durable. They're now offering me store credit to get a new bag, but they don't have any equivalent bag currently available, and won't until 2015, so I'll take them up in fall after the hot, sweaty summer is over.

I wonder if they only tested the all-plastic hardware in SF's very mild climate, as opposed to somewhere with seasons— perhaps using the bag through the winter weakened the plastic?

I also had a previous edition of the Timbuk2 Shift, which had even worse pannier hardware with 2 hooks held in by tiny little pins as its only points of support. When one of the hooks fell off because its tiny pin slipped out, I was very lucky the bungee the bag had didn't get caught in my rear wheel and cause a crash, which would have been especially bad in lower Manhattan traffic.

So, I guess my answer is: I suggest the Ortlieb as they're a lot more experienced with manufacturing/sourcing durable pannier hardware. Or maybe look into the Arkel as well: http://www.arkel-od.com/us/messenger-pannier-laptop-bag.html

If you do want the Shift, REI has it:
http://www.rei.com/product/847594/timbuk2-shift-pannier-single
And it's nice to be able to take advantage of their return policy, if you need it as I did.


Apollo gradient rear bottom frame mount pivot point After only 6 months of use the bottom pivot point has developed play where the rear frame section is rocking from side to side I have looked everywhere for what is causing the problem and for the replacement parts to fix this problem with no success your help would be greatly appreciated.

If it's only 6 months old, take it back to the shop as it wasn't fit for sale.


Which mountain bikes are purposefully built to be 27.5 and 29 compatible, similar to Rocky Mountain Pipeline I'm looking to get a bike that was designed to handle both 27.5 and 29 wheels so that i can have a single bike and swap wheels when feel like modifying the riding characteristics.
I was looking at the Rocky mountain Pipeline that was designed to handle both wheel sizes and has a 9 position flip switch to help adjust the geometry based on the wheel size being used.
Was wondering if anyone knows of other companies and models that are designed with this same option in mind.
Thanks.

27.5x2.8 and 29x2.4 have approximately the same outside diameter of the inflated tire. Same with 27.5x3 and 29x2.5-6ish. All 27+ bikes can run 29; it's implicit whether they're marketed as such or not, although many are. In the other direction, bikes presented as native 29, there may not be enough side clearance for a 27+. Older 29ers would typically not have that kind of clearance to spare, but the whole 27+/29 interchangeability thing got big around 2016 and many made since then have it.


Grx 10 speed problem I have a new 10 speed grx group set. The right hand shifter have only 9 gear. I check the problem is in lever,i felt in high gear it was making a big jump.
Are there any suggestions for someone who is having a similar problem??

@ArgentiApparatus is correct - 9 clicks is 10 speeds.  Your lever starts at one end, in a gear position, and the first click puts it into the second position.  Thus there is one fewer click than gear positions.
You definitely have a 10 speed shifter, confirmed by  https://bike.shimano.com/en-EU/product/component/grx-10-speed/ST-RX400-R.html
There remains the possibility that the shifter is somehow faulty, or that your indexing is not correct.


Gear cables replacement - inline barrel adjusters I'm in the process of ordering replacement gear cables for my road bike which has 105-5800 groupset. My existing cables have inline barrel adjusters and I was wondering:

Are the inline barrel adjusters reusable? (I'm not opposed to replacing even if they are)
If I have a barrel adjuster on the rear derailleur, do I really need an inline adjuster as well? (I need to verify setup for front derailleur)
Is there an optimal position on the cable for them to be installed?

Yes. Barrel adjusters are reusable.
More useful for the front mech which doesn't have any on-the-fly adjustment.
And useful for the rear mech for quick adjustment without having to get out of the saddle.


Does this rim tape need to be replaced? I replaced my very first tube ever after my tire went flat yesterday. I successfully installing a new tube, inflated it, and left it overnight.

This evening the tire was still fully inflated, but after a little riding the tire rapidly deflated again. The new tube has a large tear right at the valve (and after inspecting the old tube, that is also where the tear is.

Inspecting the wheel shows this is what the valve hole looks like:

Was this the cause of the puncture, and would replacing the rim tape resolve this issue? Or is that normally how it looks?

The issue is I don't have a reference of what this part of the rim tape should look like.

One way to get tears around the valve stem is by not supporting the pump head and stem while you're pumping up the tire with a frame pump (the kind where you are pushing on the stem as you pump up the tire, like in the photo below).

Notice the way the person's left hand is holding the pump and the rim. The idea is to stabilize the head of the pump so that no stress is placed on the valve stem.


Lock jammed - key will go in and out but cannot turn I know that similar questions have been asked here, but I can't find a question with the exact same problem encountered here.

My bike was left locked during a week or two of sub-zero temperature, and another week when my wheel was punctured (almost three weeks I think). And the day I started riding it again, I felt the lock started to jam but managed to lock the bike anyway.

Now since a week ago I cannot unlock it: The key goes in but doesn't turn at all (I bought the lock less than a year ago). I've suspected that water froze inside the lock, and so I've applied some water displacer in it (gt85) which has worked last time it has jammed, but not this time.

Is there any hope to unlock it if I use a lubrificant? And what type of lubrificant should be used?

I've finally managed to unlock it thanks to the WD-40 penetrating oil, which the bike shop I bought the lock from advised me to use.

I suppose it was getting a bit rusty inside the lock mechanism, that's why the key couldn't turn.


Bottle on frame alternative I've been riding with a bottle filled with isotonic drink + hydration backpack with plain water for quite awhile. Recently my bottle stated to fall off on descents (not the best frame design + increase in speed). I'm looking for alternatives to frame mounted bottle cage that will suit aggressive trail riding. Solutions like Source dual bladder won't fit, because once you had a sweetened drink in your bladder it's just a matter of time before mold starts to grow there. I've looked on runners belts, but 600ml is way too little for hot conditions. Assuming I want to separate between sweetened electrolyte drink and regular water, and a minimum of 1l liquids all together, what are my options on the market nowadays?

First of all: You mention that the placement of the bottle mount is bad. There are adapters which allow you to mount a bottle cage without frame holes. E.g. SKS Anywhere, Minoura or this set. All look rather flimsy though. Mounts for the handlebar or behind the saddle usually look more sturdy, if you have space there.

There is also the Salsa Anything Cage which allows you to mount and tie down anything anywhere.

If a better, more vertical mounting point for your existing bottle cages doesn’t solve the problem, maybe you should get better bottle cages. For example I use these Elite bottle cages with various normal ~800ml bicycle bottles on my cyclocross and I’ve never lost a bottle (except in a 40km/h crash, but that doesn’t really count). They also seem quite popular.


Poor shifting in dense fog? I cleaned up my bike yesterday after a particularly wet and muddy week, wiped the oil off the chain, applied a fresh batch, took it for a spin and found no issues whatever with the shifting (I go through all the front and rear cogs to make sure the oil is distributed evenly).

This morning, however, on my way to work, shifting was a complete nightmare, it felt like either the chain was skipping or the derailleur was ghost-shifting (likely the latter). The only thing I could put it down to was the dense fog and the permeating humidity. Is that possible? Could it have somehow affected the oil on the chain?

I would suggest temperature change may be affecting the cable housing dimensions, which in turn affects the cable tension and therefore the dérailleur settings. I have been noticing this happening to myself this fall, especially switching to a bike with full length housing and 10 speeds on the rear dérailleur.  With the large daily temperature changes in fall I find myself adjusting the rear dérailleur tension by a quarter to half-a-turn in either direction depending on how the temperature has changed.  (Luckily the bike has inline adjusters near the bar, which makes this a trivial exercise).

Metal will expand or contract with temperature, and therefore the dimensions of the cable housing (which has metal strands) and the cable itself can change slightly with temperature changes.

For what its worth I never noticed this issue on older bikes with 9 speeds or lower (with or without full length housing).  I have however started noticing this issue with full length housing and higher speed drive train (i.e., 10, and 11 speed).

Solution/Hypothesis Test:

If you are handy at adjusting derailleurs, then you can test this hypothesis and potential fix the problem at the same time.  The next time the shifting problem emerges try adjusting the derailleur.

If it happens in the fog, you will likely have to add tension/elongate the housing by loosening the rear derailleur adjuster. If the shifting improves, then half the hypothesis has been verified (H1: cable housing contraction in colder weather).
If after (1) the weather warms up and the shifting goes off again, try tightening the rear derailleur adjuster (effectively shortening the cable housing).  If this fixes the shifting then consider the second half of hypothesis verified (H2: cable housing expansion in warmer weather).

Bike Geek Aside

As an aside, the expansion and contraction of the housing and cables will counter act each other to some degree (e.g., contracting housing will lessen cable tension, but contracting cable will increase tension).  Each component will also expand and contract at different rates.  My anecdotal experience seems to suggest the expansion and contraction of the cable housing has the biggest effect. Another big effect I have found was adjusting the cable tension inside, where it is warm, the riding it outside where it is cold would quickly throw all my setting off.


What would happen if I don’t replace worn drivetrain components? What would happen if I took a entirely new drivetrain and just never replaced anything? Of course, I’d keep it clean and lubricated.
With 11 and 12 speed chains being as expensive as they are, the old adage of “replace the chain to protect the cassette and chainrings” starts to make less and less sense. If I skip two new chains, I save the cost of a cassette. Another skipped chain would cover new chainrings.
In other words, skipping three replacement chains would save me enough money to just buy an entirely new drivetrain. That is better than the normal approach, which -for the same money- would give me four worn out chains, a worn out cassette, and worn out chainrings.
Importantly, this avoids the issue of having a new chain on a worn cassette or some other combination thereof.
What are the downsides to my logic? I can think of a few right now:

decreased shift performance
increased risk of chain breakage (by how much?)

In my experience - breakage is not directly correlated to wear.  I've had bikes with unknown mileage on them, and have chosen to ride the transmission into the ground.
Generally the performance slowly deteriorates, with chain slip under power being a sign that things are getting bad.
Unlike other answerers, I've never had a worn transmission break and strand me or injure me.  The only time I snapped a chain is because I didn't reconnect it properly, and that one was perhaps half-worn.  I have twice wiped a derailleur with the rear wheel's spokes, but again that was misadjustment, not wear.
If you can afford to, replacing parts often helps maintain things in top-top shape, but for those of us with real world demands on our wallets, you can go quite far into the worn stage before it gets too much.  After all - you own it.
I find that climbs and going up grades are the most taking on the transmission and drivetrain so if its going to slip, its then, or when doing high power efforts like taking off from the lights.


Can it be estimated when it would actually be beneficial to increase drag in tailwind? Usually the advice for cycling is to try to be as aerodynamic as possible (like, reduce the surface exposed to the air in front of you) in order to decrease drag as it will cost less effort to maintain a given speed. Especially so with headwinds. However I think there might be a point when riding with tailwind where it would actually be beneficial to increase your surface so the tailwind has more effect than the resistance of the air in front of the cyclist and hence actually helps 'pushing' one forward. Is there such a point and is it possible to estimate at roughly what tailwind speed it occurs (let's say on a flat road and other factors all equal)?

Or another way to think of it, in practice: say I have two jackets, one pretty tight and a looser one which tends to form a balloon, would it ever be beneficial to choose the looser one because it increases total surface so the force of tailwind applied to it is larger than the force in the opposite direction created by the resistance to the air in front of me?

A tailwind reduces your relative airspeed and therefor the drag you generate. You can go faster relative to the ground  with the same power output. The only time increasing your profile might be beneficial is if the wind is traveling faster than you are, relative to the ground .... Unless you cycle slowly or the wind is very fast, it's usually not the case. This is cycling, so aerodynamic is mostly about reducing drag, unlike sailing where maximising lift is important.


What features make a disc brake caliper unsuitable for use with other than resin pads Shimano says its Tourney mechanical disc brake is "designed for resin pads only".  What is it about the design of a brake caliper that makes it suitable only for resin pads?

It's not the caliper, it's the disc (it's made out of a soft material). If you put a harder brake pad, it would wear the disc too fast. Actually look at the disc. On my discs it's written: "for resin pads only".


Wear marks on chains I am generally using SRAM chains with a powerlink. For a new chain there is no indication of a preferred pulling direction or inside/outside.
If we demount a used chain that has never been taken off before at, say, about halfway life, are there obvious wear marks that show in which direction it was pulled and which side was on the outside?

Does it make sense to maintain the direction and orientation, or perhaps to reverse one or the other?

It makes no real difference - the rollers in a chain turn all the way around, and the wearing surface is the internal diameter of the roller, not the external diameter of the pin.

There are some fancy chains which have a marked outside and an inside, and may state a top and bottom too, but this is more about matching the shifting lands and pins and ramps on a cassette.

Some chains are asymmetric in their outer plates, which looks "wrong" if installed upside down.

Other chains, noticeably half-link or BMX chains can have plates over the top, so the two outer plates are one piece folded over.  This is done for strength, and cannot be flipped either.   These chains don't work with derailleurs so you're unlikely to have one.

 A chain that can be reversed but not flipped.


How to keep Presta valve insert from detaching after inflation? I have Presta valves on my bike tires and for the rear tire, each time I inflate the valve, upon detachment, the insert screws off with the pump attachment and the tire deflates.  I tried about 6 times, no luck.

Here are pictures of the detached pump connector with Presta insert detached and the valve stem with no insert:

What am I doing wrong?  How can I inflate and detach the pump without detaching the insert? I had no issue with the front tire.  Is the valve broken or am I doing something wrong?

I've had this happen with some tubes - Continental, maybe? Conti tubes are compatible with valve extenders, so the valve on them does come off like this. You're probably screwing the chuck on too tightly, and then the valve comes off with it.

Or maybe some tubes come with the valve not properly torqued.

And after it did come off, you probably didn't tighten the valve tight enough into the stem to stop it from happening again.  There should be small flats on the side of the valve portion that comes off - you need to use a wrench on that when you rescrew it into the stem.  Be sure to hold the stem with a pair of pliers when you do this to prevent the stem from twisting.  If you don't you can tear the tube.

Worst case, put Loctite on the valve threads if it keeps happening.


How do I stop my clipless shoes and pedals from squeaking? I'm riding with Shimano SD66 sandals. They are awesome sandals and it's so comfortable riding without worrying about socks and shoes. I'm using Shimano pedals.

I'm getting a squeaking sound, mainly from one shoe/pedal at the top of the power stroke. I'm almost certain it's from the shoe/pedal because just adjusting the angle of my foot a little (inside the play allowed by the cleat/pedal) makes the noise stop.

I'm assuming that the shoe and pedal are deforming/conforming to each other and have started to rub at the most common positioning.

I'd normally look at lubricating, but don't want to use grease as that will track through my house and office.

Any other thoughts?

Rather than use grease, you can try using a 'dry' or wax based chain lube.

Apply the lube to the flat clips on each pedal - hit both sides if they are double sided mtb pedals.
If you think the squeak may be coming from the pedal itself, rather than the friction between the pedal and the clip, apply some lube to the spindle attachment points where the pedal rotates around the shaft.
Wipe away any excess.
Hold onto a wall or go for a ride and and clip in and out of the bicycle pedals until the lube is adequately distributed and worked in.
Repeat all steps if still squeaking.

If you carefully wipe off the excess from your shoes/cleats and the pedals, you won't be tracking anything around your house after your ride.

If after a second application the squeak remains it may be a problem with the bearings in the pedals - some can be overhauled, but others it makes more sense just to replace.


What items should be in a bare-minimum first-aid / emergency kit? Yesterday I was hit by a car; very minimal injuries and overall a very minor accident--but in hindsight it's made me realize I was ill prepared and really should have a small emergency kit with me at all times.

This kit would be for true "emergencies" only, not bike breakdowns.  If I find myself injured--or others find me injured and unconscious--what items and information should I have with me?

This kit should:

contain the bare essentials
be very compact and convenient to either transfer between bikes or build one for every bike
durable with very little maintenance
obvious to bystanders and/or emergency responders so that it will be found and opened if need be

Water
Some sort of antiseptic, ideally something like a small bottle of Betadine, though regular ointment/cream will do fine, and it wouldn't hurt to have both
Gauze pads, in a couple of sizes
Adhesive tape
A few large Band-Aids
Some tissues or cotton pads for wiping off a wound

And, of course, cell phone, money, and ID (placed somewhere where people can find it).

I have my name, address, emergency contacts, etc on a gummed label stuck to the top bar of my bike and covered with clear tape


How often should I change my mountain SPD bikeshoe cleats? I bought a pair of Shimano PDA600 SPD pedals along with a pair of cheap-ish Garneau Terra MTB shoes in early 2012.

I wear them for my daily commute (approx. 18 Km) and semi-regular long distance rides. I also walk on the street with them - to the office, pub, etc...not very far.

The cleats when new have right-angled edges, but now they have been "worn"/"smoothed" into more curved edges.

To use they "feel" a little bit loose, but sometimes they feel quite sticky (hard to remove my foot from the pedal), so I'm not sure.

On other pedals, I've changed cleats every few years, but I rode a lot less.

Is there a recommended period of time (based on usage, etc) to change cleats on MTB shoes?

Also, is there any suggestions on how to increase the life of your cleats? (I guess one would be don't walk on the street!)

Thanks.

I have similar problems as you describe, but mine come from dirt, mud, and other things that get caught in while doing MTB.

Aside from that, the Shimano SPD pedals develop some sort of a lip as they wear out, in the side "ramps" that rise the cleat when you twist the foot sideways. It happens in similar fashion as if you repeatedly hit the end of a metal rod with a hammer, until it deforms and starts to look like a nail head. This "lip" makes it very difficult to twist the foot, hence it is difficult to release the cleat from the pedal. The solution I have implemented is to file those lips out every now and then.

Close inspection to the pedal clamp mechanism is all it takes, scratch the ramps with your fingernail and if you feel a little stop near the end of it, then you file it and repeat the fingernail test until your nail can freely slide out of the ramp... Sometimes it is so little that even sandpaper can do the job. After that, clean the mechanism the best you can with a toothbrush and apply some lubricant. Apply lubricant also when you feel it's necessary. (I do it before every MTB ride, but almost every 10 rides for city commuting)

Regarding cleats, at least for me, I never change them, my shoes usually die first, then I try to put the same cleat on new shoes, and only if the bolt is too hard to remove (happened once) then I use new cleats...

My oldest pedals are 13 years old now, in the bike I use the most (the MTB for XC and light DH), have other 2 bikes with old SPD on them (commuting or urban riding), but only one pair of shoes for everything.


Shimano SL-RS47 SIS handlebar shifter reassembly How do I reassemble the Shimano SL-RS47-7 SIS left shifter on the handlebar after it became separated after an accident? The shifter became separated and I could only get it into first gear. It does move the derailer but it doesn't have any stops, therefore, springs back to first.

Shimano calls this a "REVOSHIFT Shifter (3x8/7-speed)"  and since its the left one, its only a three position shifter.

This model line is called Tourney and is the lowest named groupset.  Its made down to a price and all the design decisions are about being cheaper and faster/easier to assemble.  Downside of this is once its damaged they're generally a write-off.

You could spend ages and still not fix it.   Instead I'd suggest you replace both rotary shifters with an equivalent pod or trigger shifter like the Tourney SL-TX50 left and right.

They will have a thumb lever to drive the chain up to the larger sprocket and a push button that drops the chain to a smaller sprocket.  The left one is 2 or 3 positions, and the right one could be 6 or 7 or 8, so do make sure to get the same number as whatever's on your bike now.

I'd also suggest taking the opportunity to replace the two gear inner cables for a few dollars.   And optionally treat yourself to a new pair of handgrips because the old ones will have to come off anyway.

Left shifter as documented at https://bike.shimano.com/en-US/product/component/tourney/SL-TX50-L.html


One crank arm won't come off First time taking the cranks off. The bolts, chinrings and drive side came out easy. Left is stuck. Should I open, pull or do something particular for it to come out?

You must use a Crank Arm Puller tool:

Park Tools Crank Arm Puller

Here's how to use it:
Video


Is there a bicycle designed for slow riding? I enjoy my road bike, but recently my children have become old enough to ride, but still very slowly.  I'd like to be able to ride with them on all or mostly flat pavement, but the road bike just isn't pleasant for slow riding as it takes more effort to balance and isn't that comfortable.

What type(s) of bike is well-suited for very slow comfortable riding like this?

Any bike with a comfortable seat, upright riding position and low ratio gears.

This is pretty much the definition of a 'cruiser' style bike.

Many hybrids, less expensive mountain bikes and fatbikes would fit the requirement too.


Shimano MT500 leaking from bleed port My rear Shimano MT500 hydraulic disk brake has acting up for a while. After doing a full bleed and new set of pads it would be fine for about 2 weeks then start rapidly losing performance and screeching. I did this a couple of times to see if the problem would appear in the same way which it did, noticing oil on the pads each time.

I put a bit more time into bleeding the rear brake again - now when the brake lever is pushed fluid seeps out of the bleed port. This is happening even with the cup still on the lever and the system still open! Surely the pressure should be releasing from the top port which is open?

During the bleed I noticed when I pulled back on the bleed port syringe there as a lot of small bubbles and it felt like no air would release and the pressure would snap the syringe handle back in, though it seemed fine when pushing fluid out towards the brake lever. Could something be blocked?

I'm supposed to traveling with this bike on Saturday so I'm not sure if its worth just purchasing a new back brake now in case it's unlikely to be repaired on time? It's cheap enough to be worth it if required though I'd likely have to fit it myself in this timeframe, which I've not attempted before though does appear somewhat straightforward (though so did brake bleeding!).

It could be an easy fix, or a new brake. Are you prepared to trash your travel plans over the cost of new brakes?  Given the time frame, I would either hand it over to my LBS, or put on a new brake and sort it out when I got home. Time frame for sourcing a new brake means any hiccups and you won't have time to sort it unless you buy from your LBS. Your best option is probably get the LBS to do the work as well.

If you replace the caliper on its own you will still need to bleed the brakes. Replacing the entire brake assembly, if you get one with the correct length hose, should require no bleeding. Shimano (Don't know abut others) ship with the hose detached from the lever so you can install into the frame if needed. Installing a new brake is much simpler than bleeding, especially if you run the hose on the outside of the frame.

Only thing you really need to decide is what quality brake to buy. Your could go cheap - say MT365, with the plan to fix up the MT500's later, or use this as an opportunity to upgrade to M596 or better. (Going to M596's you should also upgrade the disc rotor to the narrow shimano version - MT500's use the wider Shimano rotor)

I recently needed a new back brake in a hurry and got discounted MT365's with a view that the $US20 cost could be saved by waiting for a discont on XT's. I still have not upgraded, the 365's are not great brakes, but for the rear give me enough power an modulation for my style riding.


Hand signaling while decelerating I'm nervous about hand signalling (taking a hand off the handle bar) while I'm decelerating: I'm worried that my body being pushed forward will act on the one remaining hand and change the angle of the front wheel.

So I'm sometimes not signalling as much as I'd like to (e.g. while I'm decelerating): as much as I would in a car.

Is this a known problem? Is there a work-around or solution?

This is for riding in city traffic. For example on a main road, relatively fast with cars following, I want to slow down before turning off onto a side street.

Yes, it's a known problem, at least to me. The work-around is not to signal, or to use head-turning and lane positioning as a signal.

What I do is very dependent on the situation. In the worst case, fast moving traffic on a busy, multilane road with no bike lane/bus lane/parking that would allow me to slow down out of traffic I will overshoot and just pull in at the next opportunity. If I knew about it in advance I'd avoid that road. My experience of signalling and slowing down, forcing the moronist behind me to also slow, is that it doesn't help. I get signals back, shall we say.

Cyclists in Melbourne do signal more than they do in Sydney, but rarely to motorists. The most common is the right arm out "I'm pulling out in front of you" which when done assertively works almost all the time for persuading motorists to let you turn. (left arm/move left for countries that ride on the right hand side of the road). The slowing down signal I don't recall ever seeing except in primary school.

Signals between cyclists are much more common, but that's because they're safer, easier and the following cyclist is more likely to notice them.


Trek Verve 3 disk bike Just purchased a Trek Verve 3 disk bike.  Had to take the front wheel off the get it in the car.  Put wheel back on when arrived home and took it out for a spin.  The front wheel makes a rubbing or grinding sound when I ride it.  Thought it was supposed to be a quiet ride.  What is going on?

The first thing to check is if your wheel is slightly misaligned in the dropouts. Disk brake tolerances are pretty small. From the web it looks like the front wheel has a quick release. Try untightening the wheel and reseating it in the dropouts.
If that doesn't fix the grinding noise, you should check if the pads have adjusted too far in or the brake rotor is slightly bent.

What can happen is that the brake lever was pressed in while the wheel was removed and the brake pads have auto-adjusted too far in. Generally, people put a special spacer in the brake when the wheel is removed to avoid this problem. The fix for this is pretty easy, use a soft plastic tool ( tire levers are good for this ) to slightly push each brake pad back until the inserted wheel rotates freely. Then pump the brakes hard several times to "reset" the auto adjust back to where it should be.

Lastly, the disk rotors might have gotten slightly bent during transport. ( dropping a wheel and having it land rotor side down is common.)

Pick front of the bike up and spin the wheel, watch the rotor in the brake an see if there are significant wobbles. Truing a disk rotor isn't the easiest task for a novice bike mechanic, but a good shop should help you with this for a newly purchased bike.


Is it possible to add a TT shifter to Di2 junction box? Is it technically possible to add another shifter to an already functioning Di2 setup, allowing for an extra shifter at the end of an aero extension bar, hooked up to the same junction box as the original shifters, to allow the rider to shift in three different riding positions (normal, drop, aero)?

Yes, of course, that's possible. You just plug the cables into the brifters. Peel the grip-covers forward and you'll see unused ports underneath. Those may be used for sprinter buttons or for climber buttons as well.

But I'd suggest you replace a triple box by a quintuple box (Shimano SM-EW90-B 5 Port Di2 Junction A) to make the connection easier without undoing and replacing the bartape. Another advantage of the quintuple box is the fact that you can remove the aero extensions without fuss.


What is this bike tool? I've bought a saddle bag with a set of bike tools; stuff like alan keys, puncture repair kits,  spanners etc. There's this one tool (well two but they screw together) that I have trouble recognising.

I know for sure it's not part of the installation of the saddle bag. It also didn't come with any instructions.

Its a Chain tool, the long bit should screw into the back (bottom side in the pic) of the other bit to provide a handle. You can then put an hex key into the twisty bit at the right hand end.


Reverse FTP measurement Often it is argued that an 8 or a 20 minute effort can be sufficient to estimate Functional Threshhold Power (FTP), an indicator of how many watts a rider can put out over the course of an hour (or 40 minutes, depending on who you ask).

For a 20 minute effort, it is often argued that a 5% reduction over the 20 minute wattage gives an accurate estimate of the maximum wattage for the 40-60 minute effort.

For the 8 minute effort, an additional 5% (for a total of 10%) is taken off the total wattage over 8 minutes.

My question is as follows: does the reverse also hold? Suppose I do an 80 minute test, or a 160 minute test, will a respective 5 or 10% increase in the wattage over that period be my FTP?

As a rough rule of thumb, those ratios are approximately right but there is quite a bit of individual variation and there will be more individual variation in the mean maximal power to FTP ratio at shorter durations than at longer ones.

If we consider a mean maximal power curve, a plot of the maximal power one is capable of sustaining plotted against duration, it is generally pretty flat from 8 minutes out to many hours. It's not of course totally flat and there are various individual factors that influence the shape of the curve. The slope is greater at the shorter duration, and it has more individual variability there.

This example curve taken from Jack Mott's website shows (note time is on a log axis):

Now while this is the general shape of a MMP curve, there is individual variability and I chose this image as it gives some clues as to why, namely the contribution of the various metabolic energy systems that supply the energy varies depending upon the duration of a maximal effort, and also upon the unique physiological characteristics of the individual.

So while long duration efforts are dominantly fuelled by aerobic metabolism, during shorter maximal efforts there is a greater contribution to the energy demand by anaerobic metabolism, and anaerobic capacity is highly individually variable.

As a result, the ratio of short duration power capability to FTP can vary quite a bit between individuals, while the ratio of long duration power capability to FTP will be less variable.


What is the purpose of so many gears? My bike, which I love dearly, has 21 gears, which appears to now be standard among mountain bikes. Is that truly better with a bike that has, say, 7 gears? And why is it that the amount of gears a bike has always a multiple of 7?

There's a good article here which explains it pretty well - although there are 21 gears there are only effectively about 11 distinct useful gears on a typical 3x7 gear setup:

That is to say, some of the gear combinations overlap (or near enough) and this means you don't really get any extra function from them, but having them can make gear changing up/down a range smoother because it means you have to change the front sprocket less often. The exact number of "useful" gears will change based on the number of teeth you have in your particular setup, but the principle is the same.

As you can see from the graph, you do gain extra range from having an extra front sprocket - if you only had 28t on the front then adding a 38t gear gives you 3 extra useful gears, then adding a 48t gear gives you another 2 on top of that. This is good but it's not really the same as adding an extra 7 useful gears each time.

Also as some others have mentioned, gears don't always come in multiples of 7, this just seems to be the most common number of gears in the rear cassette of most mass-market bikes.


Will a 11-speed cassette fit my Giant SRC 3 frame (~2007) I would like to upgrade an older Giant SRC 3 (~2007). Having a very limited experience with bike mechanics, how will i find out whether a 11-speed cassette will fit the frame and or the wheels?

Presumably you are planning to upgrade the older frame to a newer complete 11 speed groupset. Makes sense as 105 rim brake groups are relatively inexpensive now.
In 2007 11 speed road groupsets didn’t exit, so we can assume your Giant had a 10, 9 speed or less groupset, and a 10 speed or less compatible hub.
When 11 speed groups were introduced the width of the splined free hub body on the hub was made a little wider to accommodate an extra sprocket. This means 11 speed cassettes will not fit on your hub, so you need new wheels with an 11 speed free hub body.
However, some wider range cassettes can overhang the inboard end of the free hub a little and will fit on a 10 speed hub (a spacer is used on an 11 speed hub), but of course you need a long cage derailleur to work with the wide range cassette.
FYI, frame dropout spacing didn’t need to get wider for 11 speed groups, still 130mm for rim brake setups.


Front gear issues with middle ring (not always making it over) I've been trying to straighten out some shifting issues on a kid's bike, it's a Diamondback and is a few years old. On the front gear-set it has a few issues that I am having trouble fixing through l and h screw adjustment and indexing.

When shifting from the small ring to the middle it doesn't always make the shift, I have to twist it a little past the audible click to ensure a shift.
Also it's shifting into the big ring way too early. When moving the shifter about halfway to the audible click it's already moved over, letting go at this point results in a downshift.

From what I'm interpreting fixing one of these issues would make the other worse. Does anyone have some tips?

On the shifter handle, get the adjustment nut all the way in(where cable connects to the handle). Now get yourself some new brake outer and inner cable. Lube it very well, with oil(not grease, nor WD-40)

Now for derailleur, one screw is for the lower limit, the other one is for the upper limit. This is to ensure that the chain will not go out of the gears

Now shift into the lower gear, and fix the cable on the derailleur as tight as you can but without moving the derailleur. Once this is done you just need to use the adjustment nuts on the handle or the derailleur. I like adjusting it from the derailleur as the first fine tunning and any other from the handle, so I can keep track of how much wear the cables have.

Also check out if the derailleur is straight and parallel to the chain rings.  If it's not, it will not shift properly.


Does chain tension change how hard/easy it is to pedal? I ride a single speed bike and it seems to be tougher than it should be to pedal. It is comparable to one of the higher gears on a multi-speed bike. I'm getting the feeling that my chain may be too tight.

It has a 44:16 gear ratio.

Would a looser chain make it easier to pedal?

Obviously you don't want the chain too loose or you risk having the chain pop off.

If the tension is too high, the drivetrain will bind. If it is too low, the chain will drop (which is dangerous on a fixie, since it can catch and lock up the rear wheel relatively easily).

You basically want the highest tension such that the drivetrain doesn't bind.

See Sheldon Brown on how to set chain tension properly.


Should I replace all wheel bearings when only some are worn? I just ripped apart my mom's mountain bike's rear hub.  One of the bearings was incredibly rough, so I replaced it, and the other one was smooth, but didn't turn very easily.  Since I didn't have a replacement for it on hand, I just put it back, but I'm not sure if I should try to replace it.  Is there a good rule of thumb on bearings?  Does one failed bearing imply that another one is likely to go soon?

While we're at it, should I be doing anything to the freewheel other than cleaning it and re-greasing it?  I've heard it's important not to put too much grease inside the freewheel, or it'll increase drag when you're coasting, so I was careful of that.

The specifics for this bike:

Mavic wheels
Shimano 9-speed freewheel
Full suspension mountain bike that gets fairly heavy use on XC singletrack terrain

According to Lennard Zinn's book 'Zinn and the Art of Road Bike Maintenance', you should replace all of the bearings even if only one is obviously bad. That way you ensure round, smooth, consistent bearings. I've been using his repair manuals for years and he's pretty much never steered me wrong.


How do I fix a left crank that has come off of my Pro Form 4.0 RT Stationary Bike? The left crank has come off of my Pro Form 4.0 RT Stationary Bike. It is about 8-10 years old although up until this year, I would estimate I put only 200-300 km in total on it. This year I have put 800 km on and most of that in the past 6 weeks. I normally ride at a resistance setting of 12 and in recent weeks, I was really pushing my self to pedal harder to get my speed up. Prior to the crank coming off I noticed a repeating clicking (more of a repeating thud and I could feel it when I pedalled). This was only on the left hand side. The right is smooth as silk. To be clear, the problem is where the crank connects to the bike (the pedal connection to the crank is fine)
I eventually tried to see what was wrong and after a lot of attempts tried to tighten the crank with a hexagon ratchet screw driver. The first time, I simply tightened it and I thought everything was good. But very quickly, it got loose and the screw came right out. I put it back in and tightened again and then the same problem occurred again. When I look at the bolt it does seem ok but the Crank end that is held in (where it connects) does seem to have some rounding to it on one of the corners and there are some medal shavings on the floor (though not a alot).
So I am looking for advice on how I could fix this. I would note that I am not mechanically inclined and normally just take these things into the shop. However, in this case, it would be very difficult to get the stationary bike out of the house and I worry if I dismantle it, I won't be able to get it back together. Plain language would be helpful to me as I did not even know the part was called a crank until I starting looking for help. All help is much appreciated.

As mentioned in comments the crank arm is wrecked and needs to be replaced. Once the square taper hole in the crank starts to deform (and yours is quite bad) it's impossible to get them to stay on tight and the problem gets progressively worse.
If the axle square taper is undamaged you should be able to simply purchase replacement crank arms. The square taper interface is standardized. There are a a few complications for someone not used or equipped for working on bikes.

There are two similar square taper interface standards JIS and ISO. The angle is the same but JIS is slightly longer. The vast majority of bike components use JIS, but it's worth checking. A JIS crank will bottom out on an ISO taper.

The Pro Form 4.0 RT stationary bike has all the drive stuff hidden away internally and used two 'left hand' cranks. If you wanted matching cranks you have to buy two left hand ones.

To get the right hand crank off off you need a special crank puller tool. Video shows how they work but there are various types available.

The retailing bolts need to be tightened quite hard (~30NM). You really need a torque wrench to make sure you get them done up tight enough and avoid repeating the problem.


Gear indicator on SRAM X5 Shifter shows wrong gear I have SRAM X5 Shifters like this one:

The indicator is now showing the gear above the one I'm actually in, so if like the picture it shows a 2 I would actually be in 1 (the smallest chainring), a 3 showing means I'm on the middle chainring and no indicator means I'm on the biggest chainring.

I've tried searching for tutorials on overhauling the shifter in the hopes that these would include the gear indicator but all of the ones I've found seem to deal only with the actual shifter part of the array and not the indicator.

Does anyone know if it is possible to fix the gear indicator? Can you point me towards (or give me a run through) of how to go about fixing it if it's possible to do so?

Other than showing the wrong gear everything else about the shifter works fine.

I don't know if you're still having this problem, but this could be useful for others, so I'll go ahead and answer it.

To be honest I wouldn't bother trying to fix a gear indicator, especially a front one. It's not difficult to remember which chainring you're in and opening up the shifter is definitely going to invite problems for inexperienced mechanics.

What Chris said is probably wrong: the gear indicator will not be affected by cable stretch.

The above notwithstanding, this is a very easy problem to remedy.

1) Shift the chain to the lowest chainring (least cable tension).

1.5) Slide the shifter off of the bar if possible. (This step is not strictly neccesary, but I find it makes things easier.)

2) There should be a number of small allen key heads around the top of the shifter. Undo these and carefully remove the top cover of the shifter. Take a picture of the internals in case anything falls out.

3) The top cover is composed of the cover and the bar clamp (which contains the gear indicator). All of the working parts are contained in the lower part of the shifter. In the middle of all of these you will see a cog which is raised up and doesn't appear to mesh with anything. This is what drives the indicator. On the underside of the top cover you will see a toothed strip of plastic: this is the indicator. Slide it with your finger to '1' (which is where you should have shifted to at the start).

4) Put the top cover back on and put the shifter back on the bar.


Is it possible to convert a press fit bottom bracket to threaded? I have a road bike with a press fit bottom bracket (I'm not quite sure which kind). The guides I have watched make it seem fairly risky to replace and requires ~$250 worth of tools to replace. I saw online there seems to be some products that can convert a press fit bottom bracket to a threaded one.

Do these work? Are they worth using?

BB30 and PF30 have press-in adapters available that have ISO aka BSA aka English threads. They do work but they mostly exist for the purpose of being able to run a certain crank that you wouldn't otherwise be able to, and to a lesser extent to address creak. (I don't have a very refined opinion on how good they are at doing the latter).

BB86/92 and conceptually similar pressed standards (BB90, 95, others) are by nature too wide for this sort of approach to work.

You can make a very effective bearing press for all types of press-in bottom brackets out of threaded rod and some nuts and washers. If you got the right diameter rod to interface snugly with the bushings in the Park BBT-30.4 or 90.3 (for example), you could just get those and skip buying a shop-type press, and you'd have lost nothing but a little bit of speed. (Improvising tools to do the whole job for cheap is kind of a larger discussion and I'm tempted to write more, but it's probably off-topic for this question.)


Bottom bracket lock ring loose - how should I tighten it I can feel so laterial play when grab hold of the crank arms then wiggle it side to side. I discovered the lock ring  was very loose. So much so i could turn it with my fingers without any effort.

When I tightened the lock ring just by hand, the play went away. I loosened it then it came back.

Does this mean my bb is unscrewing itself from the frame and i need to tighten it up?

Is this a job for a  newbie home mechanic to attempt?

Loosen the lock ring, then tighten the bottom bracket cup until the play goes away and the crank moves smoothly. Then hold the bottom bracket cup in place and tighten the lock ring.

There are special spanners you can buy for this or you can use an adjustable spanner to move the bottom bracket cup and a screwdriver tapped gently with a hammer to tighten the lock ring. You may have to improvise further with your choice of tools. You may also need an assistant.

A newbie mechanic should have no problems doing this. If you don't try you won't learn.


What thread is the rear wheel axle nut? My father is trying to repair his old '65 (we think) Schwinn 3 speed. The only problem is he has not been able to get a replacement nut for the rear wheel axle. Local hardware stores have been unable to identify what kind of thread it has, and we've had no luck finding any info online.

Anyone know what it might be, or how/where to find out?

Your rear hub would have been manufactured by someone other than Schwinn. Given the age it was probably manufactured by Sturmey-Archer or Sachs (now SRAM). Those links contain links to small parts for both hub brands.

Sheldon writes:

  The axle threading of most SRAM internal-gear hubs is unusual, 10.5mm x 26 TPI, but close enough to that of many Sturmey-Archer hubs (13/32 x 26 TPI) that Sturmey-Archer axle nuts are usable in a pinch.


Cheapest and safest way to clean MTB drivetrain? I've got a CUBE Attention MTB which has been serving me well, but out of a lack of knowledge I never bothered to degrease the chain before relubing it, so over time there has been a build up of gunk and hardened material that I haven't really noticed because my whole drivetrain is black.

I've heard people telling me to degrease it with WD-40 and then simply relube it but this doesn't seem to be a good idea. What are your personal tips and tricks regarding this?

Cyclingtips has a nice deep dive into this, albeit it appears more focused on road bikes. The author’s take is that you can simply wipe the chain off after every ride without degreasing, then re-lubricate occasionally. The author believes that if you just use degreased on a rag, then all you get degreased mixed in with the lubricant, so your chain is actually less lubricated.

MTB and gravel bikes will get more dirt intrusion into the rollers, that road bikes, but even road bikes will get some. That dirt forms a grinding paste which increases chain wear. Thus, many people will benefit from getting an on-bike chain cleaner. This houses brushes and a lubricant reservoir (NB: dilutes dish soap will suffice). You can run your chain through it, and it will get it cleaner that simply wiping it off. You would then let the chain dry, then re-lube.

Naturally, there are more thorough methods that are detailed in the article. You should not allow yourself to be intimidated by them. Simple methods are enough for almost all riders. But yes, you could remove the chain, soak it in solvent (perhaps in an ultrasonic cleaner), then lubricate it or dip it in wax. But you do not have to do this.


How can I fit this bottle holder to this bike? I want to fit this bottle holder on my bike but the attachment seems too thin for the frame tubes. I believe this is a universal bottle holder and my bike isn’t of unusual size or tube girth. Am I missing something here or this just won’t fit?

P. S. Unlike my mountain bike, this bike (Claud Butler Legend) does not have pre-drilled holes for accessories on the frame.

That does not appear to be a attachment for mounting a bottle cage to a frame tube. The two holes in the mount appear to match the two holes in the upper plate of the cage, which orients the mount incorrectly for clamping a frame tube. My guess is that it's for mounting to handlebars - which have a standard diameter, unlike frame tubes.

mounts for frame tubes do exist. They typically use two adjustable straps of some kind to accommodate different size frame tubes. You want something with a beefy strap that can be tightened sufficiently to stop the cage rotating on the frame tube.


Cross tires on a road bike I want to buy a road bike for commuting, fitness, leisure, etc. and not for professional racing. However, because I live in a "wet" country, I would like to be able to change the tires into cross tires.

As far as I know, standard road tires are 25mm and standard cross tires are 30mm.

Are there any entry level (meaning less than 2-3K) road bikes that have the frame/fork/brake clearance for the larger wheels?

The main thing to watch out for is the brakes, if the comes with V-Brakes or Cantilever brakes, you should be able to run wider tires and fenders.

Typical CX tires are 32-35mm and typical road from 23-28.

The caliper style brakes found on many road bikes will not accommodate the wider CX tires. There are many options under 2-3K, You could even look at cyclocross bikes as many are under the 2-3K in the US. Visit your local bike shop and look at a few options.

A buddy bought a Kona "Jake The Snake" last year and is a very nice bike and under the 2-3K.


How to create a bicycle that rolls backwards when you pedal forward? This may seem like a crazy question, but I am currently trying to design a kinetic machine where pilots are facing away from the direction of motion, adding whimsy and curiosity. As someone who doesn’t have a lot of experience with redesigning bicycles, I am struggling with coming up with a functional design where the gears of the bicycle could still be changed. The first idea I had was to arrange the chain in a figure eight shape, making the back wheel of the bike turn backwards while still pedalling forward. Although I haven’t prototyped this design, something tells me that having the chain cross like that would create too much resistance to reliably change gears. Another idea is to add an extra gear between the pedals and the chain, changing the direction the chain is going entirely. However, I’m not sure if the size of said gear would interfere with gear ratios on the bike? If anyone is interested in helping me out, I would greatly appreciate it!

I refer to a bike throughout, though I suspect you're actually going for something with more than two wheels, and likely more than one rider.

Multi speed bike gear systems generally can't be driven backwards. This means that if you really want gears, the chain that drives the rear cassette or hub gears must move forwards. Fixed gears are designed to be driven backwards for braking.

You could easily choose to go for fixed gears on a machine like this, in which case your figure of eight chain would work, but you'd want a chain tensioner with guides in the slack side, so the chain doesn't touch itself at the cross.

If you really want a range of gears the best thing would probably be to install a geared hub the wrong way round. This would need a left side chain, but you should be able to achieve that with tandem or BMX components (tandem parts are more likely to be compatible with other types of bike).

This approach would leave the bike as effectively a front wheel drive, rear steer machine, which would be very unstable. You might be better off driving the bike as normal (rear wheel drive, front steering) and turning the rider round. This would be (conceptually) as simple as clamping a saddle onto the top tube and putting your figure of eight chain in place as above, but would work with normal derailleur gears as the chain would be pulling correctly. A single chainring and a couple of idler sprockets with guides would be a good idea to maintain reasonable angles in the vertical plane.

For a little inspiration you might want to read up on the retro direct drive. This had one gear ratio pedalling normally and another driven (still forwards) by back pedalling, and the bike could still freewheel fowards.

Your point about intermediate gears is easily dealt with by making both gears on any intermediate axle the same size.


4 punctures in one week, even after replacing tube and tire, what's happening? I've just had my 4th puncture in 8 days on the bike I use to commute to work. Same back wheel each time. I haven't had a puncture before in the 2 years I've had this bike.

After the first puncture I replaced the tube.
After the second puncture I repaired the tube.
After the third puncture I replaced the tube and got a new tire.
Two days later it's punctured again.

What's strange is that the punctures - tiny, like a thin needle - have all been on the part of the tube facing the tire. They have all been randomly spread around the tube with respect  to the valve. Both these seem to indicate it has nothing to do with the rim, and yet with a new tire it's still punctured...?

Any thoughts?

(I'm considering the possibility that someone is sabataging my bike while it's parked in my university parking, though there is evidence against this also.)

The answer to my question -- why did my bike puncture four times, even after replacing the tube and tire -- turned out to be: bad luck.

The first three punctures were caused by some damage in the tire (the punctures on the tube were all on the tire side). After I replaced the tire, I got another puncture - but this time the puncture was on the part of the tube facing the rim. On inspection I was that my rim tape was protruding up at the point of the puncture. Because I had a new tire and tube I had pumped the wheel up more than usual, which perhaps meant that rim tape protrusion was now a problem.

So, four punctures in one week: three from the tire, one from the rim.

For anyone else experiencing a confusing series of punctures, consider that you may be unlucky and that there are multiple problems in your wheel!


Can I ride a big bike? I am a MTB beginner and I just bought a used Giant stance 2. I knew from the beginning the bike is bigger than I should have, but it was a good deal. The bike frame is XL and I am 6’. Based on Giant size tables I should be 6’3”. I feel slightly stretched, but I don't feel bad on the bike, but I also haven't been on the bike for a long time.

What is your opinion about the bike size? I heard most people saying that is better to buy a smaller bike than a bigger bike, but my concern is if I will be able to ride the bike and have fun anyways. I suppose I will have to put more effort in stuff like manual, wheelies, but I should still be able to do that right?

EDIT: I am 24 so no longer growing.

There are a few things you can do. I would be very surprised if the XL is that much too large it cannot be setup to be ridden by you reasonably comfortably, if not ideally. A bike that is too large may make some technical trails a bit more challenging, so how successful you are on that bike will depend on the type of trails you ride and what you expect to be able to achieve.

Aim here is to reduce the effective top tube length. Here a few $0 Cost, completely reversible things you can try.

Move the seat forward on the rails.
'Slam' the stem - put the stem on the steerer first and put the
spacers on top (can arrange stem and spacers any way you like).
If riser bars rotate the bars a little.
If really wide bars, as is popular these days, move the controls and grips inboard. This narrower position effectively 'lengthens' your arms.

Other things that might help if the above fails that cost a bit, but not a lot of money.
 - Flatter bars
 - Higher bars
 - Shorter stem
 - Longer seat

If the seat won't go low enough, trimming the seat post will help. If you find a position that works, you may consider trimming the bars or replacing with narrower ones. I would hesitate to recommend trimming the steerer as unlike bars and seat posts (which can be relatively cheap to replace), The forks are an expensive bit of kit.

Personally I suggest play with the above setups, get the bike as comfortable as you can. If you find after a few months its limiting your riding, it probably best to sell it and book this one up to experience. A bike that does not fit well is never a bargain.


Why do bikes have carbon forks? I have noticed many bikes for sale that are made of mostly one material, such as aluminum, except for the fork which is carbon. I know carbon is very expensive so the manufacturer must be trying to use a little bit in the best possible place. So, if for a certain price point they can choose only one part to be carbon, why the fork? What are the advantages of carbon forks?

There are an intersection of a number of reasons:

Public Perception - Carbon as that "wow" factor.  Colloquial it is associated with "space age"  technologies.  Therefore it must be better!  The truth is that the performance of carbon depends heavily on manufacturing techniques used (e.g., materials and layup).  See point 3 for an example.
Weight - Carbon has a high strength to weight ratio. Carbon forks really started to take a hold when steel was still a dominant frame material and during a period in the cycling industry when there was a serious obsession with weight savings. As such, carbon quickly became got the reputation of being material of choice for building light stiff components.  Compared to building forks from some other materials (e.g., an all steel fork) significant weight savings can be had. The weight difference to other materials such as aluminum however is not as significant, but once the public perception is set is hard to go against the grain..
Compliance - Because carbon has good fatigue resistance - it can be flexed nearly an infinite number of times without failure, if the force is less that the critical limit where structural failure occurs - this means it has the potential to be very compliant, if manufactured appropriately.  However it is expensive to customize carbon, because of all the molds required.  As such, many carbon components are intended for a wide use case (e.g., rider weight) and therefore are typically overbuilt for most people needs due to the failure mode of carbon being catastrophic.  As such, carbon forks (which are often lauded for compliance)  can also be harsh.  It really depends on how the part was manufactured and what your weight and use cases are.  Just buying a carbon fork does not guarantee a compliant ride.  For example, the most compliant fork I have ever ridden to date was a thin walled steel fork, it soaked up high frequency road vibrations like you wouldn't believe. My modern 2017 all carbon "endurance" bike with a "compliant" fork comes pretty close, but the difference is still noticeable (which I attribute to accommodating for disc brakes and thru-axle).
Ease of manufacturing - As others have pointed out in this thread, forks are separate components so it is easy to use another material here, especially if you can order forks at a good price. This makes it a relatively cheap upgrade on the production line especially considering point (1).
Economies of Scale - Because carbon forks have been popular for so long now, manufactures know how to produce them relatively cheaply now.  As such, this again makes it an easy upgrade (see previous point).
Quality cannot be visually determined - It is difficult (impossible really) to determine the manufacturing quality of a carbon fork by looking at it.  You need to scan or cut it apart.  This means that manufactures can opt for the cheapest fork possible but still maintain a look of high quality (assuming point 1).

From a functional/practical stand point I think there are many instances where carbon forks do not make sense (e.g., commuter bikes), but manufactures include them because of the public perception out there (which ironically manufacturers helped create). For most regular bikes, I think a steel fork is a more sensible choice: It typically offers a compliant ride and is more robust to physical damage than carbon; but many would view a steel fork as a step backwards simply because steel is colloquially viewed as an "old" material.

Don't get me wrong, I think you can build a very nice bike out of carbon (my daily ride is one), but I think carbon is at its best when it is tailored for its use case, which typically means more higher end bikes.  I would personally skip carbon on lower end bikes as I don't think it provides any advantages as manufacturing and use case coverage dictates that it is often over-built with cheaper layups.  The problem with carbon fiber is that as a consumer you have no visual way of telling whether the carbon fiber fork (or frame or whatever) you are looking at is of a high or low quality, both will typically look identical.