23 mm combined with 25 mm tyre in racing I met a guy who mixed 23 and 25 mm for his front and rear tyre respectively.

Now thinking about it, I believe it's a pretty good idea since the rear wheel bear a higher proportion of the rider's weight. Wider rear tyres would support more weight with the same pressure as the front. It also helps reduce the wear and tear on the tyre itself.

So why don't bicycle (especially racing) run a slightly wider tyre in the rear, as the rear wheel mostly bear the weight of rider? It makes the ride more comfortable, and not aerodynamically terrible as the front is still 23 mm.

I would be genuinely surprised if it made any real-world difference.  Some racers commit all sorts of voodoo... err... questionable practices on the off chance it might give them an advantage. In terms of 23 vs 25 mm tires, both sizes are frequently used by pro tour teams, if one had a distinct advantage over the other you wouldn't see both sizes being used at the same events.  It terms of aerodynamics, even for sizes up to 32 mm  there doesn't seem to be much difference in   aerodynamics drag.

In terms of comfort getting the right tire pressure for your body weight will likely have a bigger effect than 2mm gain in the tire width.

Other disadvantages include complications  introduced into the assembly and supply chain for the manufacturer, which would eat into profits.

Racing is all about speed. 25mm tyres have a larger contact area so there is more rolling resistance than a 23mm. It doesn't make a huge difference but it is significant. You wouldn't be competitive on 25s with everyone else runnings 23s.

But for some very tough terrain, such as going over cobblestones, most teams will often run 25s front and back. They  also deflate slightly from the maximum pressure to avoid some of the ride harshness.

I started on 28mm tyres on a commuter and soon went down to 23mm. Didn't notice any difference in tyre wear or comfort. Bike was less effort to ride. Only downside is is that it is more likely to catch a rut in the road, but you ride with a bit more caution.


How to avoid riding on a gravel on the road sides? + Riding through traffic lights I'm commuting to work almost every day. The roads on my way are quite thin so I have ride on the edge of it. But there is usually some gravel and it's quite hard to ride on that especially when riding up the hill. I don't like riding on the gravel but I don't like blocking cars behind me. What should I do?

Other thing is riding through the traffic lights. While waiting for green sign I'm not sure if I should be in row with cars or just wait on the right side of the road so I don't take much space. I don't like taking a lot of space as cyclist but also I don't want to be in danger if some driver doesn't notice me when I'm on side of the road.

Any tips that will make me feel better riding on these roads?

Depending on your local regulations, claiming the lane might be illegal (it is here where I live, for example). So, my advice would it be to ride on the right side of the road (assuming that right is the driving side), but not getting too close to the curb because of the debris, gravel, car doors etc. When you see (and hear) someone behind you wanting to overtake you, just move some to the right (and optionally give him a sign with your hand).

However, don't go to the right if you see that they can't overtake you safely, i.e. if the road is too narrow there, or if you see a car coming from the other direction.

On the traffic light, claim the lane! That will prevent drivers cutting you from behind, while it doesn't bother no one (you occupy less space than a car, and they are not waiting for you, but for the light anyways). When the light opens, and you pass the intersection, return to the right part of the lane.

Traffic laws are a way of communication with the others that share the lane. When I find myself riding in a dangerous situation, I normally start what I call defensive riding.
My point is that the bicycle driver is the last safe driver at the road. So, the driving rules do not protect them as they should. This depends on the country. And of course, of the way that the citizens care about bicycle riders...

The most important thing is to make yourself visible to the other drivers. So, dress with a reflective suit. That would also, protect you from dust and other things that might happen during the ride. And specially, to direct the drivers' vision to yourself preventing accidents. At night, wearing lights would also help.

Where space is not available for bike riders, I use to drive at the opposite lane. Yes, it sounds crazy, but consider that I could watch all the vehicles that are approaching and take measures beforehand. There, rules change. I am not only standing away of the driver's rules but I have to acknowledge that nobody is expecting to find me coming from that direction. I should then, be very cautious at every corner or at any change of the normal lane.

Knowing all that, I find it safer than letting other cars and buses crush me like a sandwich because the are not watching when I am passing by. Or cars that use the power of their engines to do big accelerations compared with my small efforts when lights change.

People should consider bicycles for normal driving. And make special driving rules for bicycles that would allow a fair competition on the road shared with more powerful vehicles.


Looking for an old fashioned bicycle with coaster brakes & hand brakes for a woman I am looking for an old fashioned style bicycle. I had a bad accident on a new bicycle and I feel safer with with an old-style bike. I've never crashed before and I've been riding bicycles for over 40 years.

They are still made! Try a search for "bicycle coaster brake." You can narrow it to a "woman's" frame by adding "mixte" or "step through" or "woman's" to the key words. If you want gears add "3-speed" or "internally geared." Those searches will get you quite a range of bikes – from retro beach cruisers to very modern urban bikes.

Once you find some that appeal to you, post some links. There are plenty of folks here who can help you evaluate the differences between them.

Finding a mix of step brake and hand is not going to be easy

You may want to consider disc brakes.  They have more power and are WAY less effected by rain.

By old fashioned women do you mean step through?

disc with set through


10 speed rear derailleur only shifting 7 gears....losing my mind OK, so I have a rough and ready road bike (Planet X London Road) that is not shifting right....

It is running:

Shimano Tiagra 4600 Shifters (3 x 10) but running it a 1x10 with one front chainring

Shimano Deore RD-M610 (RDM610SGSL) 10 Speed Derailleur

Shimano Tiagra 4700 10 speed rear cassette

It shifts through the first 7 gears without issue but uses all 10 clicks to get there.  It does not reach up to the last/top 3 gears (even though it will when I move the derailleur manually by hand).

I have tried with another Tiagra road shifter and it produced the same results.

I have set up the high/low limit screws correctly, tightened the cable multiple times and set the jockey wheel height correctly.  No difference.

I have connected a MTB 10 speed shimano thumb shifter and it goes through all 10 gears perfectly.

Any ideas?  It is driving me quite mad!

I believe your problem is a mismatch of cable pull ratios between the shifter and derailleur.

The rear derailleur actuation ratio is how far the shifter cage moves for a unit length of cable pulled. The amount of cable a shifter needs to pull for each gear shift is determined by the actuation ratio and the spacing between the cassette sprockets.

Generally, Shimano road 10 speeds and below and mountain 9 speeds and below used the same pull ratio (the exception being Tiagra 4700). Road 11 speed  and MTB 10 and 11 speeds require more cable to be pulled for each gear shift as it makes it easier to get the accuracy required out of the shifters to index more closely spaced sprockets.

Because you have a 10 speed MTB shifter it's mismatched with the road derailleur. Presumably you got the MTB derailleur because you wanted to be able to run a wide range cassette, but you are using a road cassette anyway. Simplest fix is to get any Shimano 10 or MTB 9 speed derailleur (but not Tiagra 4700) that can accommodate the largest cassette sprocket you want to run.

You already got great answers here is some other good reading.
http://blog.artscyclery.com/science-behind-the-magic/science-behind-the-magic-drivetrain-compatibility/


Should I change the tire and tube or can it be patched? Someone deliberately pierced the rear tire of my fixed gear bike. It's a 700cX25 tire with 700cX18-23 tube inside. As you can see from the image the threads have come out. I am not sure about the severity of the damage. So what should I do of the following remedies:
1. Replace both tire and tube
2. Replace the tube and patch the tire
3. Replace the tube and leave the tire as it is
4. Patch both tire and tube

What can you afford?  If you're not really struggling financially you should replace the tire.

If you cannot afford that (or if you need a temporary fix while you're obtaining a new tire) then you need a "boot" inside the tire.  A "boot" is some piece of flat material (typically about 5 cm x 5 cm, though size can vary based on tire size) that is flexible but still stiff enough to resist the pressure of the tube trying to poke through the tire.  You can buy purpose-made boots made from plastic or rubber, you can cut your own boots out the (thin) sidewall of an old road tire, or, popular in the US, you can fold a dollar bill up several times and use that.

The boot is used by inserting it into the tire after the tire is mounted and the tube is in place.  Pry the tire off the rim near the hole and slide the boot in between the tube and the hole.

Using a boot is not as reliable as replacing the tire, of course.  There is a danger that the boot may shift over time, especially if the tire pressure is not properly maintained.  And a boot is an even less reliable fix for a hole in the sidewall of a tire.

The tube is actually less of a worry than the tire.  If the hole is a puncture rather than a cut/slit, or it's a very short slit, then you can patch it with conventional tire patches.  If the cut is so large that a standard bike patch will not comfortably cover it (with maybe a 10mm margin) then the tube needs to be replaced.

No harm in trying to get some more life out of it.

You'll need to patch the tube normally, and test it overnight.

Then you need to provide something to stop the tube bulging out through the tyre when inflated.  Personally I'd put the largest thickest patch you have on the inside of the tyre, but others would use a piece of plastic or something else durable.

This is a back tyre so a sudden blowout is generally not as bad as a front one.

I would not ride this patched tyre a long way from civilisation.

Otherwise, a new tyre is the best answer.  Your tube will be okay patched.

Finally, you need to think about what happened.  Someone deliberately did this to your bike.  Either park your bike somewhere more secure, or identify them and have words.  Have you annoyed someone lately?  I can't see how this could have been an accident.

Also, get paranoid.  Check your bike every time you return... look for flats, but also look for other damage.  Disconnected brakes would be most likely.


Can a greasy chain cause the chain to come off the rings? I heard once that you should clean your chain with a light degreaser whenever it looks especially dirty or at the very least once every few months. But that doesn't account for frequency of rides or miles ridden!

I've been riding my road bike over 100 miles per week for the last month and have been meaning to clean my chain anyway... and then...

The past week my chain kept popping off the chainrings. Four times out of five it was while shifting from the small ring to the big one. I believe it also happened when accelerating from a pretty low speed, like just at the crest of a very steep hill.

I'm going to clean my chain anyway, but I'm just curious: could a very dirty chain be causing it to pop off the rings? Or could this be a problem of technique? Or do I just need a general tuneup?

No.  A greasy chain won't cause the chain to pop off, and it would have to be exceptionally dirty for dirt to cause this.  (I've ridden many miles with greasy, dirty chains.)  Generally a chain comes off due to maladjustment or because of a worn component (usually a cog).

Poor technique can contribute to the problem, but the technique either needs to be pretty bad or there needs to be another contributing factor.

Yes, too much grease can pop chains, especially when shifting gears. When I first started biking seriously, I thought lots of grease was a good thing because it made the pedaling feel smooth. That was a bad idea. I got stranded in the middle of nowhere with my chain constantly slipping off so bad that the only choice was to ride the same gear or remove the grease. I used a spare cleaning cloth to wipe off most of it and it was fine the rest of the ride.


Retrieving Loose Nipple from Inside Rim So I have a wheelset that I really like, only problem is the first time I rode the wheels a nipple came off the spoke when I launched off a speed bump going downhill.  For a long time it was silent (the nipple must have been stuck in some stan's or something) but recently its come loose and rattles all over the place when braking.  I am pretty sure this is going to drive me crazy.

Looking for strategies that people have found successful for getting a nipple out in this situation.  I figure if worst comes to worst I can take the tire off, remove the valve core and put a dab of rubber cement in the rim that will hopefully catch the nipple.  But I'd like to fish it out if I can.

If you take the rim tape off you should be able to shake it out through one of the holes that you insert the nipples through. I've dropped a few inside rims and never had a problem getting them out this way.

If a nipple came off, what happened to the loose spoke? Have you been riding with one spoke missing?

If that is the case, then you have to get that fixed some time, and for that you will have to remove the tire ans the rim strip, getting access to the holes through which the nipples are installed in the first place. You then replace the nipple with a new one as you install the replacement spoke. (If it came of there is a huge possibility either the spoke or nipple threads where damaged in the incident).

If you got the spoke replaced already, then the nipple must have been removed at the time, if not, well, the only doable thing would be precisely remove the tire and rimstrip just to take the nipple out.

Simply consider that the nipple's head is bigger than any hole in the outside wall of the rim (the one that is visible even with the tire installed) , except for the valve hole, so there is no way of taking it out without removing at least the valve, (and there is not a single technique known to me to remove a valve that does not need removing also the tire), so I would save the mental exercise and just take the tire off.


How tight should the tandem front chain be? I have a Thorn Me'n'u2 triplet (three seater tandem), and was having a problem where whenever I tried to accelerate suddenly (either solo or with stoker(s)), the front chain seemed to fall off (happened at least once every time we went out).

I tightened it up (removed a link and turned the offset bottom bracket) so it was then pretty tight (taught top and bottom, only moves a bit when squeezing the middle), and that problem stopped happening - so far so good.

Later on tour we saw someone with a similar tandem but their front chain seemed very saggy - they were stopped, and it was drooping very noticeably both on top and bottom.  I didn't have a chance to talk to them, but presumably they weren't having the same troubles.  Does this suggest something else is/was wrong on mine, and that it should be ok with a much looser chain?

The sync chains should always be tight enough that they're not physically capable of falling off, and there shouldn't be any easily perceptible droop, ideally in any rotational position. If you pull the chain up and down, it should have a little bit of flex and "give" to it, the feeling of the pins having some aggregate movement to give in their inner plate bushings. Some sources like to give specific amounts of free movement that indicate a properly tensioned chain, but this is the wrong approach because it depends on the length and the internal clearances of the chain. Too tight is when you can feel any binding or extra friction. Sometimes parts with poor concentricity or damage force compromises where there may be some spots with slight binding/friction. On a nicer bike like this one would hope not, but it's not the end of the world.

Incorrect chainline will encourage dropping in a sync/singlespeed chain capable of it. But mostly the right answer is the chain shouldn't be capable of it, and if it is then problems are likely.

Both chains should be evenly tight. Other wise it won't work properly


Can a Sora 9 speed rear derailleur short cage support a 12-36 cassette single chain ring 56T? My 20 inch folder has a single chain ring of 56T and a 11-28T cassette, 9 speed Shimano sora 9 speed Rear Derailleur short cage. I want to change the cassette to 12-36T for some hill routes. Based on my understanding the Derailleur capacity needed is
biggest chain ring - smallest chain ring + (biggest cog - smallest cog)
= 56 - 56 + (36 - 12) = 24.

I am not sure the capacity of the short cage Sora 9 speed, because different source gave different info. And they all assume a double or triple crank set which is not the case here. So will my RD support a 12-36T cassette?

I've done this. You need to fit a small nut on the end of the longer B screw because the change in angle means the screw misses the frame. the nut essentially widens the screw.

According to  this page, the tooth capacity of the short cage version is 31 teeth. But let's look at a road bike with a relatively small gear range. you're likely to find. Filling in your formula, we end up with

52-39 + (23 - 12) = 24

Even the smallest cage derailleur would most likely cover that range.  52-39 is a standard road double crankset, and although there are smaller cassettes, they are quite uncommon. I would say that just about any derailleur could cover a 24 tooth range.


Single Speed / Fixie - Chain tension / uneven tension I recently changed my chain and noticed it has uneven tension (probably my chain ring being out of rounds). I followed Parktool's video and set the tightest spot to have about 0.25 inch movement up and down.

I wanted to confirm that I did everything correctly, it’s been sort of hard for me to judge if the tension is correct. I’m also not sure if the noise that the chain makes is normal, or if it’s too tight. I have attached videos for the tension and noise.

I would appreciate it if someone could confirm if everything seems good? Thanks!

Chain tension (I start the video at the tightest spot)
https://imgur.com/a/7CFWc0b

Chain sound:
https://imgur.com/a/8fgiLlH

I'm going to disagree with Mike and say that chain is far too tight. I race singlespeed MTB and have a fair amount of experience setting chain tension. In the fixie/singlespeed world; a loose chain is a fast chain, but not TOO loose. There is a "Goldilocks" tension to chains where the chain can freely move up/down along the drive line but not enough to jump teeth on the cog or chain ring.

All chains will "stretch" over time and require periodic re-tensioning but a chain that is set too tight will exacerbate wear on cog, chain ring, and the links.

FWIW, I run oval chain rings on my MTB and those are even more finicky to set up. Tension is set on those when the oval portion is at its widest position on the y-axis, then goes slack through its rotation, but never slack enough to de-chain or skip teeth.

Just an example of my chain after a race earlier this year where you can see how slack it was but still connecting and putting power to the tire.

Nice bicycle.

I don't hear anything weird, it's the sound of fixie/single speed.

However the chain is too lose in my opinion. For your reference the total slack (up and down) should be less than USB type-A plug width and I get the impression that it's double in the tightest spot, to say the least.

My experience with chain tensioning is to "finger-tighten" (tension the wheel with one hand while operating the wrench with the other) it in the tightest spot gives you required slack.


Help identify mid-90s steel MTB frame If anyone knows what this frame is and could help me identify it, I would be most grateful.

Distinctive (or not) details of the frame:

Seat tube top: is concave, curved in.
Rear brake cable routing: brazed-on noodle on the seat tube.
Seat post binder bolt: is behind the seat tube.
Top mounted cable routing: the shifter cables and the rear brake cable are routed along the top of the top tube.
Head tube: the reinforcement rings.
Rear derailleur cable braze guides: are under the seat stay.
Ritchey rear dropouts: incl. flat (vs round) seat stay and chain stay ends  & eyelets.

Measurements:

Weight (approx.): 1.886 kg
Steerer: 1 1/8 inch
Seatpost (approx.): 26.6 mm
BB (British): 68 mm
Dropout spacing: 135 mm
Top Tube (approx.): 590 mm (c-c); 615 mm (effective); 28.6 mm (diameter out)
Seat Tube (approx.): 435 mm (c-t); 390 mm (c-c); 28.6 mm (diameter out)
Head Tube (approx.): 110 mm; 36.5 mm (diameter out)
Down Tube (approx.): 32 mm (diameter out)
Chainstay (approx.): 420 mm
Reach (approx.): 460 mm

Serial Number: B99XXXX (B plus 6 digits)

Other (Ir)Relevancies:

Came equipped with a threaded 1 1/8 inch triple butted (TB) rigid
Kona Project 2 (P2) fork.
Originally from Germany.
Preliminary discussion: http://www.retrobike.co.uk/forum/viewtopic.php?f=1&t=377616

Close matches so far:

Many Scott mid-90s models.
Biria MX 700, but round seat stay and chain stay ends and 27.2 mm seatpost.

All input appreciated, any ideas or suggestions are most welcome.

Thanks

I owned a Ritchey steel frame from ~1999 and this doesn't look like a Ritchey of that era to me.

The cable stops are welded to the top of the frame.  Mine were welded underneath.
There are no lugs on the frame.  All the Ritcheys I have seen from that time had lugged frames.

My guess is that the frame was built by someone else using Ritchey dropouts.  I would think those unusual looking cable stop clusters might be a clue, but maybe they're more common than I am guessing.

There's more info here that seems to indicate (though not definitively) that the serial number doesn't match the pattern of that time for Ritchey, and that the company was in fact selling parts to other manufacturers.

There appears to be a "Ritchey" name tag and emblem on the rear drop outs. While Ritchey currently sells components to a variety of manufactures I can't find any information on when they started doing this. I would assume that a frame this old with Ritchey components was sold as a Ritchey complete bicycle. Identifying the actual model may be impossible as many time the frames were used in different models with the drive train components being the main difference.


How to deal with lock that keeps jamming? I have a kryptonite U lock and lately it's been sticking a lot while trying to turn the key. Usually I can eventually get the key turned. It was getting worse though and a few days ago I (unable to find any lube/wd-40 etc) cleaned it out with soap and water which seemed to help a great deal. I also started being very careful to make sure the little key-hole guard engaged. Last night when I was totally unable to get my bicycle unlocked and had to leave it there and walk home. The key would fit into the lock and turn half way and then stop. I'm going to go try and pick it up now, but I don't know the best way to try and make sure this doesn't keep happening. It's winter here and I wonder if that might have something to do with it.

Edit: I ended up at the hardware store and the guy there (who had built his own bike in his garage, conveniently) recommended jig-a-loo. This made the lock move really well but I still couldn't get it open. This is when I noticed that my key was twisted (From trying to force the lock probably). I flattened the key back in a clamp and was able eventually to unlock it, but I can't seem to lock it again, so I ordered new keys. I'll have to wait till they come to see if that solves anything or it's actually a problem with the lock...

Edit again: Some graphite and new keys seemed to do the trick!

You can follow the advice in this thread to get your lock off, although my guess is that the lock was either damaged from washing it or water has frozen inside the lock.

Once you get it off, if the lock is damaged, Kryptonite has a lifetime warrantee on their locks. I'd call them up and ask if they'll replace it.

With your key in place, jiggle the lock and key

I've tried everything else. The most simple solution worked out the best!


What makes the bicycles in Amsterdam suitable for riding with jeans on? What makes the bicycles in Amsterdam suitable for riding with jeans on?

The Dutch are known to wear regular clothes while cycling rather than cycling specific clothing.

In cycling forums, people often say that jeans are uncomfortable for cycling especially in the rain. When jeans are wet, friction increases which can cause chafing and increase the wear and tear on the jeans and the saddle. The Dutch must have a way of wearing jeans comfortably since regular clothes include jeans. Cycling friendly pants tend to be silkier and thinner so that friction decreases, and more flexible so that there's less pressure on our perineum. Even with a saddle cutout, the seams on jeans can put too much pressure there.

I'm thinking that these are the possible factors:

Saddle height
Saddle setback
Upright posture
Cadence
Power
Coasting percentage
Saddle shape
Pants sold in the Netherlands tend to be more cycling friendly such as
jeans with softer seams
The commuting times are too short for the discomfort to develop

Also, can you have a fast or powerful human powered bike that's jeans friendly? Like hybrid, cyclocross, MTB, and road bikes.

Someone who's into fitness and speed, bikes to work, and wouldn't want to carry an extra pair of pants would be interested in getting that answer.

In places where there are lots of bikes, most people who are riding them are making short journeys purely for transport. For a short ride of a few kilometers, it really doesn't matter what you're wearing. Any clothes that are comfortable to wear in general will be comfortable to wear on a bike for fifteen minutes.

People who are riding longer distances, pushing harder and aiming for fitness rather than just getting from A to B will start to consider clothing that's more oriented towards exercising and people who are going even farther and pushing even harder will start to wear cycling-specific clothing.

I see this exact thing when I cycle at home in Oxford. If I cycle directly into town, most of the people I see on bikes are just wearing whatever clothes will be appropriate at their destination. If I take a more circuitous route around the outskirts of town before heading into the centre through an area where not many people live, I see a lot of people wearing "general exercise" clothing. If I head away from town, out into the countryside, most of the cyclists I see are wearing clothing designed specifically for cycling.

In Australia it has seeped into our culture, unfortunately, that riding a bike is a sporting activity, which should be done in appropriate cycling attire, preferably in packs, and with some aggression. I'm exaggerating of course, but it is "a thing". The question is probably coming from a similar perspective. Even though I have recently started commuting to work, which is a 60km round trip (note my good old bike is now a pedelec), I refuse to wear cycling specific clothes, and I also refuse to wear a helmet*. Cotton shorts and t-shirt are fine most of the time, and there is no need of a helmet as I am largely on bike trails or paths, and I feel I must have some Dutch DNA, as riding is as natural to me as walking, skipping and jumping - I have a very strong tendency to remain upright and on my bike.
I think the upright riding position is a key ingredient for a comfortable and safe ride, even at 35km/h, and particularly when riding in jeans, in the rain, holding an umbrella.
We have a lot yet to learn from the Dutch about bikes, riding and urban design.
* see freestylecyclists.org


Why are disk brakes not completely round on the outside? Why are disk brakes not 100% round? Why is the outside edge "rough"?

Here's a pic of what I'm describing:

For the brakes to self clean and remain effective, the surface of the pad must transition from metal to void at least once every revolution across the entire pad (i.e. no continuous line of metal). The 'sawtooth' rim achieves this. Some very cheap disks do not achieve this.

You may find the very good answer by @trailmax in this question useful.

I'm relatively confident in saying that bike disk brakes have such outlines because it makes them look "cool" or "fast".

The great, great majority of car disk brakes have no holes, and they work fine. "Performance" car disk brakes have holes and/or slots, but they are absolutely not required.

The general reasons for holes or slots in disk rotors are:

Improvement of cooling, by increasing surface area and breaking up laminar airflow, as well as (for car rotors) adding an additional airflow path.
It can serve to reduce the rotating weight of the brake disk.
In wet or dirty conditions, it helps water or dirt escape from the brake-pad brake-disk interface, which improves braking performance in such conditions.

As such, while holes or other shapes cut out of the actual brake surface are reasonable, I can't think of any good reason for the non-circular outline, except perhaps some minor improvement in cooling due to it acting like a blower fan a little tiny bit.

Note that this is not a vented rotor, but rather a cross-drilled rotor. Car disk brakes do have internal ventilation, but it runs parallel to the brake surface, rather then through it.


How often should hydraulic disk brakes need bleeding? The brake handles for my disk brakes became very loose four months after I bought the bike. The bike shop bled the brakes and put new oil in them, which sorted it.

They're feeling a bit loose again (6 months later), but not as bad as last time. I use my bike most days cycling for commuting (6 miles) with longer rides of around 30 miles once or twice a week.

How often would you expect to have to bleed your disk brakes and if you had to do it more often would that suggest there was something wrong.

If the brake response gets mushy, also check the brake pads. Personal experience: I saw no need in bleeding the brakes before changing the brake fluid (on a DOT system). Maybe your system is not sufficiently sealed?

The need to exchange the fluid depends on the type that is used in your brakes. And this should be self-evident: Do not, under any circumstances, change the type of fluid used in your brake! It will most certainly degrade the gaskets.

DOT

If your brakes use DOT (classified by the US Department of Transportation) brake fluid, i.e. "DOT 5.1", the fluid should be exchanged every 1-2 years [1]. With time, the fluid absorbs water, affecting its compressibility. This is by design, since non-absorbed water would affect the compressibility even more.

Mineral Oil

Mineral oil, however, does not need to be changed so regularly. Unless you open the system, the oil stays good for up to 6-7 years [2].

[1] Bosch Automotive Handbook, 7th Edition, ISBN 978-0-7680-1953-7
[2] http://www.magura.com/de/produkte/scheibenbremsen-2012/prod/mt2/info/faq.html

As you use the brakes and the pads wear down, the oil will heat up and expand. This pushes oil back up into the reservoir, and when the oil cools off the pistions will suck away from the rotors.

Look at the brakes and you'll notice the pads probably aren't floating against the rotor as they should be, but when you squeeze the handle most of the motion is moving the pads to the rotor. When pads and rotors are new this doesn't happen because the pads are thick.

Bleeding doesn't help this, as it's normal as pads wear. The pumping you do during braking doesn't move enough fluid back into the lines to get the pads to set back next to the rotors.

The quick, easy and proper way to fix is to take the wheel off, and continuously quickly pump the handle until the pads meet in the middle of the caliper. When you can't squeeze any more then you've loaded the lines. Then using a clean flat tip driver, gently pry them open just slightly enough to get the rotor back in. Your brakes will feel like new and should feel good for awhile longer. The more your pads wear however, the more you will have to perform this little reset.


Tubeless vs Tubeless ready I've decided to upgrade to road tubeless. Hutchinson sells both "Tubeless" and "Tubeless Ready" tires. According to Hutchinson' website, Tubeless Ready means that (in addition to having a special bead) the tire's tread is air permeable and will gradually lose air, so sealant is needed, not just to seal punctures, but to slow the loss of air.

Their Tubeless tires, on this other hand, have a butyl lining that prevents air loss. Although a sealant can be used to seal punctures, it's not required.

My question: Do tubeless tires -- the tires that have a lining -- hold air as well as tires with tubes? (Note, my car's tires don't have tubes and they hold air quite well.) I ask because I need my tires to stay pumped up, and not go soft overnight the way they usually do on my mountain bike.

Proper tubeless (UST) tyres do indeed hold air well, but are also heavy and don't roll as well (due to extra material that needs to deform around objects).  Due to the nature of MTB'ing you are also likely to need sealant for puncture protection, as whilst UST tyres are more robust, they can't shrug off all potential punctures.

This is why you see very few UST tyres available for sale now, with most riders (and manufacturers) preferring tubeless ready.

In my experience, a well set up tubeless ready tyre with sealant holds air at least as well as an old tyre/tube combo.  I typically lose ~2psi/wk on my tubeless ready setups so usually top them up once a week, but could go 2 weeks if necessary.

For years I've used Hutchinson Fusion Road Tubeless on Easton EA90 SLX tubeless road rims. I do not use sealant, since once you get a build up of dried latex in the wheel rims, it's hard to get a good, airless, rim fit again. I just carry spare tubes. This gives the comfort and road grip of 90psi.

When new, the tires are EASY to get on the rim using tire lubricant or soapy water, without any tools. On the road, when putting a tube in a flatted tire, as long as you leave one tire rim engaged in the wheel, it's easy to fit it back on with no need for tools. There is a knack to doing this, and it depends on getting the tire rims properly into the wheel channel designed to be used in fitting the tire. But once you get the knack, it really is simple.

Getting the tire off the rim needs two (plastic covered) levers and the start can be particularly difficult.

I find I need to put a few pounds (4 or 5 maybe) of air in every few days, so there is some leakage, but it's very minimal.

It's a bummer that Hutchinson have abandoned the Road Fusion Tubeless and will only produce Tubeless Ready in future. I am going to try their Intensive road tubeless tire, though reviews complain about it being very slippery in wet weather


Why is cross chaining 'bad', but 1x is OK? When you run 1x, aren't you basically force to cross chain?

One key difference is the design of the chainring. A traditional ring is made to allow shifting, which means there’s specially shaped teeth and protrusions that will pick up the chain and help lift it in to the next gear.

Cross chaining with traditional rings will put the chain in the angular region where it ‘thinks’ you want to shift (ie. these mechanisms will start hitting the chain plates).

On a 1x system a narrow wide ring is typically used, or a similar device, that meshes more completely with the whole chain link. Since it doesn’t have to worry about shifting, it’s only worried about retention, so it can ease the chain into a consistent position from a wide variety of angles.

As for the rear derailleur, they’re designed to rectify the angle as well, with SRAM opting for a more eccentric pulley position relative to the pivot, and Shimano using differently shaped parallelograms. Both these systems keep the pulley a consistent distance away from the sprockets, so the whole system can accommodate wider chain angles.

https://www.velonews.com/gear/gear-issue-friction-differences-between-1x-and-2x-drivetrains/

The more you deviate from a perfectly straight chainline, the more friction you will experience, and the smaller the rear cog you are driving, the more friction you will experience.

1x drivetrains exist because the cycling industry makes more money reinventing the wheel to lower production costs, while forcing consumers to buy into new standards.

Without continuously changing, marketing hype, and designed incompatibility, many more cyclists would be able to hobble perfectly good used parts together into functional bikes, and new bike sales would decline.


For a slightly warped wheel, is it worth getting it repaired? My son has a relatively cheap kids mountain bike, no suspension or anything flash, and after a minor crash into a friend the back wheel is slightly out of true. It only causes issues under braking when the warped area of the wheel leads to stuttering braking, and locking up entirely when the brakes are pulled hard.

My gut feel is that I should just throw it and get a new one, as I don't know how repairable these things are.

Can bike shops repair that sort of thing?

Trueing a wheel is something you can do on your own, but until you get good at it it'll take you time to do it right - "carefully tighten the spokes on the opposite side..." is kind of an oversimplification. Typically a trueing stand is used; the wheel is placed in the stand and prongs or arms on the stand determine exactly where the wheel is out of true.

The problem is that sometimes you need to loosen some spokes to get enough play to pull back against the deformation enough to straighten it out. Someone who does it all day makes it look easy - you bring your wheel in to a good bike shop and usually it takes longer for you to describe the pothole you whacked into than to actually true the wheel. If you've got a good relationship with them they may not even charge you for a 10 second job (karma would demand an offering of beer or pizza as appropriate).

If you don't have a trueing stand but you're feeling adventurous you could try doing it with the wheel in the frame - stand behind / in front of the wheel (so you're looking at the tread) and spin the wheel slowly - you should see where it comes out of true. Use an actual spoke wrench - if you use pliers you can round the ends of the spoke over and if you use a wrench you'll put too much torque on it (I have a friend who has done it with a leatherman in the middle of a ride but he also repaired and managed a bicycle store for many years).

Since it's an inexpensive wheel if you're confident enough in your abilities I'd say go for it - worst case is you end up replacing the rim, but you may learn a new skill in t he process.

This can easily be repaired (unless the rim has a dent). You can do it yourself: Just carefully tighten the spokes on the opposite side where the brake pad rubs ...

EDIT: This is a cheap mountainbike with a slight dent we're talking about, not a Cervélo to be ridden at 70km/h. Of course you need a truing stand and an alignment gauge and whatnot to get it perfectly straight again, but since the rim probably isn't perfect anymore and the whole point is to stop the brake from rubbing against the rim, I still suggest to simply put turn the bike upside down, release some pressure of the tire so it doesn't explode and place a thumb on the chainstay (or fork) and put the nail close to the rim. Now spin the wheel and remember the spokes where the tire rubes on your thumbnail. Tighten those coming from the opposing side gently. If those spokes are too tight, release the ones one the side, where the rim rubs. Repeat several times till the result is halfway decent. Bike shops charge big bugs for this and it really isn't rocket science.


Why does my cantilever brake squeal *nearly* all the time One of my bikes has cantilever brakes on chrome rims.  With dual compound Koolstop Eagle 2 pads braking is adequate and I can rely on the front brake at least in the dry.

The back brake squeals like a stuck pig.  I could easily make it stop, but it's a much more effective warning than a bell or a shout when someone steps out in front, or when the lights change while passing stationary traffic. I like this feature.

I'll restrict this to dry conditions as wet rims obviously change the behaviour. I can drag the brake lightly without squealing, or lock up the back wheel, but intermediate braking almost always produces a loud squeal for quite a range of pressure.  My issue is the almost.  This morning was dry, and I tested over a number of stops without using the front brake.  All were from around 20 km/h (10--15miles/hour) and were planned but fairly sharp stops. Excluding when I skidded the back wheel on a dirty bit of road, it squealed with no thought on about 80% of the stops.  On the other 20%, no modulation could produce a squeal.  Why?

I have cantilever brakes on my bike so I know the feeling. They just seem much more likely to squeal than any other type of brakes I've owned.  In the spring I had a bit of squealing. I cleaned off the rim, readjusted everything (cables, toe-in, etc.), and sanded down the brake pads a bit and everything seemed to be pretty good.

I also think it's something to do with the temperature.  Ever since the temperature started to drop, my front brake (also cantilever) has been squealing a lot. Even during the summer the first few times I would use my brakes they would squeal, but once they warmed up they seemed to work fine. I wonder if anybody makes a special brake shoe using a different rubber for cold weather braking.

I have a bike with Avid Shorty Ultimate cantis and have had the same problems in the past.  I'd start by cleaning your wheels off with rubbing alcohol or acetone to make sure there isn't grime and oil from the road causing the squeal.

Your brake pads might be contaminated already in which case I'd say sand a thin layer off the top and try putting them back onto clean wheels and try again.  Make sure to sand the pads perpendicular to the way they will grab the wheel.

Next thing is to make sure you have the right "toe-in" on the pads.  Basically, you want them pointing slightly inward so that the front of the pad grabs the wheel first.

If all else fails, you might take it to your LBS and see if they have any tricks up their sleeve.

Also, check out this question/answer as it may be helpful.


What is the benefit of fat tires on pavement? This year in my area, I've seen a lot of people using fat tires on paved bike paths and roads, when there was no fat bikes before. I also see a lot of these bikes in grocery stores. It is summer, so there is no snow.

I'm curious of the benefits of a fat tire beyond the obvious off-roading capabilities. Is it just a weird fad or is there some benefit of a fat tire vs a hybrid or a road bike?

What you're witnessing is probably a mixture of convenience and all-around-increased popularity of fat bikes, rather than actual 'benefits'

A lot of people don't have the luxury of owning multiple bikes: one for the road, one for grocery trips, one for cross country, etc. If someone only has the resources for one bike, and they chose a fat bike because they like the versatility, you can understand why they would take that bike to the store. It's easy to argue that a fat-bike can go off-road, on the snow and sand, and of course to the store. A road bike cannot do all of that.

Also, wide tires are generally more comfortable. I could shed some weight and increase my speed a little by running ~30mm tires, but I choose to run 40mm tires most weeks because they handle bumpy roads and gravel with comfort and ease.

My statement focuses only on riding on the street, which is your question.

Greetings.

I have not ridden a Harley or Honda, but consider a road bicycle to be the Honda Interceptor. The Intereceptor is quick and fast, and great for short rides and trips around the corner; however, when traveling long distances with motorcycles, riders do appreciate the stability of a heavy bike, and this is fat bike.

The first time I rode a fat bike, I immediately noticed the greater stability and control of the bike, not to mention its comfortable ride. The fat tires seemed to absorb all displacements of the road I would feel on my road bike. I felt very connected to the road, which may be because there is more fat tire in contact with the road than there is with road tire in contact the road.

Just about as soon as I got on and began riding, I was turned around, and heading back to the store's showroom, inquiring whether there were variations available. I purchased the Orange on White model out of a catalog, and had to wait a few months to get it. I didn't mind because I was convinced that I would never have another flat again. To date, it has not let me down.

When it was assembled and ready for delivery, I was struck by how handsome of a bike this was. The photos in the catalog do not do this bike justice. I would get compliments, sometimes multiple compliments, every time I took the bike out.

I should add: This fat bike is a street bike, which comes with a lifetime warranty from Giant. It becomes void only when the bike is taken off road. The lifetime warranty is a tremendous value added to the purchase.

I guess the Rocker 3 was engineered to be a city cruiser, which explains to me now, the casual design for the water bottle holder with the frame, and the emphasis of the Momentum line.

On flat ground, the bike has quick momentum, quickly getting up to speed. However, you will notice even the slightest uphill incline as the extra weight of the bike immediately translates into your burden for you to push forward.

I should say a primary reason for buying the Rocker 3 remains its use as an exercise tool for improving my cardiovascular health. When making the purchase, I did not consider the extra weight to be a negative. In fact, the extra weight was considered a blessing as it increased my exertion.

Later, I did modify the power train by adding a triple chain ring system, and the bike now has 21 gears.

So in summary, the fat bike is a heavy bike, and its weight brings a smoother ride, greater stability, greater comfort, and more control over the vehicle while on flat road. Uphill sucks, and the Rocker 3 continues to turn eyes, as ever.


Toddler bike seat vs. bike trailer? Our 2.2 year old toddler seems very interested in a random, abandoned bike seat we found, so we're considering some method of letting him ride with us. But I am not sure whether to get ...

A bike seat, which fits one toddler, and mounts above the rear wheel on the rack
A bike trailer, which fits possibly two toddlers, has its own wheels and attaches to the rear of the bicycle.

It seems to me the trailer is more flexible and potentially safer, since the center of gravity is much closer to the ground. I also worry that having a thirty+ pound weight on the rear rack will cause us to make more riding mistakes, and if the bike falls over, there goes the toddler.

However, the bike seat seems more fun for the toddler since he can see more of the ride and feels more like a co-rider than a passenger.

It's hard for me to decide without trying both, and right now I've tried neither. Can someone who has tried both a bike trailer and a bike seat with their toddlers share their experiences and thoughts on this? I'm interested in the pros and cons from people who have spent some time in the saddle with their toddlers using both.

I've had both. A really nice trailer and a child bike seat -- where the child sits between the rider and the handlebar (like this WeeRide Kangaroo Child Bike Seat).

My daughter was ok with the trailer, but absolutely preferred the seat.

I found with the seat in front of me, the weight didn't affect me almost at all, and if the bike was going to fall, I'd be in a much better position to protect my child (since she's directly in front of me).

We used that for a long time and never ever had an issue (and let's face it, with the kid along for the ride, you're not likely to ever ride like a madman, right?)

She's six years old, and still misses it (we stopped when she was about 3.5 yrs old--just getting too big!)

Be sure to take a look at the Weehoo pedal trailers.  I have a single and a double and love them.  Not for infants (I used a Mekaroo cargo bike then) these are awesome for kids from 3 to about 9.


What does FSR stand for in mountain bikes? What does FSR stand for in mountain bikes?

Ref: http://www.bergwerk.ch/archives/3726/specialized-enduro-comp-2013/

FSR is the name of a suspension design from Specialized. According to a FAQ, it originally stood for "Future Shock Rear". The Specialized website contains an FSR Suspension page with marketing information about the system.

Forest Service Road aka an active or old logging road


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

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

I'm looking for the following reply:

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

Thanks in advance!

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

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

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

Hope that helps.

I think your general GPS concern for accuracy is reasonable, but it is the same worldwide, not just outside the US.

The full GPS constellation is in orbit with spares, so there is world wide 3-D coverage of the planet.

It happens that there are moments in time in any arbitrary location, where the coverage could be better, and the US military has a group that actually forecasts these for their armed forces.

I.e. Do not try a precision bomb drop at a moment that the satellite configuration is not optimal.

GPS has other issues (trees, buildings, clouds) that get in the way.  As Billy ONeal notes, wheel sensors are not perfect either.  An example of GPS issues, occurred when two friends of mine with Garmin Forerunner 201's (GPS only devices) on their arms ran a known measured half marathon course side by side, and had a 4K discrepancy at the end of it!  (We blame firmware for that one).  So firmware can make a big difference on GPS devices.

I would be very interested in comparing results from a GPS and wheel sensor on a longer ride.


Problem with chain skipping without trying to shift (even with new chain and gears) I have a mountain bike where the chain intermittently skips when put under load on the middle (and very rarely on the smallest) chain ring. It is not related to shifting.

I've taken several steps to correct it including:

calibrated front and back gear shifters
replaced the chain
replaced the rear gears
replaced the middle gear at the pedals (which was the most affected)

To my great frustration the problem is still there! Could this be because of the derailer? The chain seems tight enough. Help from any gurus out there would be greatly appreciated.

Update: I've tried fiddling with the back screw on the back-derrailer (not the L/H-screws) in the hope that it was a chain tension issue but it did not help. I've also checked the chain for stiff links but could not find any. I am not able to reproduce it when not riding the bike so I am not certain where and how the chain skips. I am at my wits end and planning to bring it to a different repair shop with a sensai mechanic so hopefully he will be able to sort it out.

Update 2: Solved. See below.

The gears at the pedals are the chainrings. Replacing the middle one rather than the smallest if the smallest is where the problem happens is odd, but you've done it so move on.

In order, the things I would check now that you've done the above are:

rear derailleur hanger alignment (see answer here)
chain length (how to tell). If there's an extra link in your chain the extra slack in the lowest gear might be enough to let the chain skip. Especially if you're not in the largest rear cog at the time. Technique matters here - if you mostly use the lowest "granny gear", then shift back to the middle chainring rather than onto smaller rear cogs this "too much chain" problem will not happen.
frame damage, specifically cracks around the head tube, down tube and chainstays. In the smallest chainring is when the forces on the frame are highest, so problems will show up in this gear first. Clean the bike, then carefully check the frame for damage. If the paint is chipped or cracked paint over it (with paint or nail varnish, anything that dries hard) then do a test ride under the conditions that cause the problem and check the new paint for cracks. Any new cracks mean there's too much flex, and might mean underlying frame damage. Or possibly just that you're too heavy/strong for the frame.
try adjusting the rear cable while riding the bike. Frame flex is probably the issue here, and doing the adjustment with your weight on the bike might make the difference
try re-routing the gear cables in crossover rather than parallel. The gear cables cross under the down tube - the rear cable starts on the left hand side of the head tube. This may mean new cables. This addresses shifting while you're out of the saddle swinging the bike from side to side (lateral bending rather than vertical).
new gear cables and outers. This should have been done earlier if they're not in perfect condition. Even if they look perfect, if they're more than half a year old I'd replace them just because it'd be really annoying if this fixes the problem after I'd spent ages trying other things. It's ~$20 of parts, so it's cheap compared to what you've already spent.

With a new chain a sticky link really shouldn't be an issue, but just a question: you do lube your chain, right? Especially if this happens off road, a dirty chain might cause issues.

Edit: middle chainring, not smallest

That does change things. The "too much chain" option is unlikely, as is frame damage. I would really have to put the bike in a workstand at look at exactly what happens when you're using different rear cogs and the middle chainring. Also, check for wear/slop in the rear derailleur (can you push it back and forth without shifting the gear lever). Unfortunately it's in the "I'm not sure what exactly I would be looking for, just anything that doesn't look right".

Going to a different mechanic, especially one know to be an expert, is about all I can really suggest. Sorry.

Does it always happen when you are on the smallest 2 cogs in back.  They wear out fast if you spend alot of time on them.  Its common.  You can produce enough torque in the smallest and middle front chain rings but not the bigger.  I believe your back cogs are worn.  Try experimenting when riding with the big and small cogs in back.  I bet your little cogs are very worn (very sloped sides).


Tire popping out of rim when inflating tube This is very similar to this question.

When I fill my tubes up to about 85 psi the tire pops off the rim and the tub gets caught on the rim and blows up.  I have gone through 4 tubes in two days at this point and the only thing that seems to help is to inflate them to about 60 psi.  Even putting pressure on the tires so they seat correctly (not sure if that is the correct term, I am quite new to cycling) only works until I put weight on the bike, and then the tubes blow.

For some info, I frankensteined a bike together out of used/old parts so my rims are quite old (although relatively true after ~8 hours of work) but the tires are falling apart.  The rims are 27's (inches?) and there were really no options for newer ones at the place I put my bike together at, only 700's.

Could replacing the tires fix this?  I would like to get the tubes to around 90 psi since at 60 they are quite flat when riding.

Edit:  Some details on the tire, tube and rim.

Rim:  ~1 Inch wide at the top, ~25 1/2 inches in diameter
I couldn't really figure out how to check the bead.
Rim tape looks fine, it is some hardish plastic covering the spoke screws.

Tire:  See these images of the tire.
Supposedly a 27 x 1 1/8 tire that holds 90psi.  Not sure what else is helpful info other than the pictures of the deteriorating side walls (and the lip at the bottom that catches the bead)

Tube:  700x18-23 27x1 48 mm presta valve.  I can't find max pressure, but I am sure it is in excess of 90 psi.

Three things to check:

1, Is the bead seated correctly. It's pretty common to get tyres blowing off the rim if they're not seated correctly. That said, this usually leads to an exploding tube rather than the tyre just coming off
2, As Daniel R Hicks said, are the rims so worn they're expanding?
3, Check the rim for dings and warping as Malarky sort of says, but not just the area for the bead. You may have a bent rim

Chances are, though, that the tyres are done. The pictures would make me think they're on their last legs. I had a pair of 20+ year old ones recently that ended up in the bin as they just weren't reliable enough for me. Some things aren't worth saving a few euros/pounds/dollars over, and the contact points on a bike are some of those things for me. If the rims seem fine new tyres are where I'd go.

I looked at the picture of your tire. It's flaking apart. Your tire is obviously the problem. You need a new tire.


How do I put grips on mountain bike handlebars? I just spent the last 10 minutes trying to put a new set of grips on to my mountain bike handlebars..

The old ones came off fairly agreeably and I've got the new ones 80-90% of the way on, however, at this point both my hands are stinging from the aggressive twisting and pushing - I have tried gloves, but I feel it's best left till my hands don't hurt anymore.

Is there a tried and tested way of doing this? Or is there a knack to this that I am missing?

Two solutions I've used:

Spray the inside of the grip with hair spray. Slide it on immediately, and then when the hair spray dries, it will glue the grip in place.
Use rubbing alcohol. It does not do as good of a job at locking the grip in place, but it does evaporate quickly and doesn't leave any lubricant inside the grip.

Boiling water helped but hair spray was best


Can I fit a 26x1.25 tyre to wheel with current tire 26x2.1 I've just bought a tacx turbo trainer and want to get a tacx training tyre for my mountain bike.

Can I fit a tacx 26x1.25" training tyre to my wheel with current tire 26x2.1" ?

Thanks

Matt

I regularly run 50mm and wider tyres on narrow rims which is the opposite of what you want to do, but suggests that your actual rim width might be narrower than you think it is. Viz, you might find that you have 25mm or narrower rims, in which case a 32mm tyre is perfectly reasonable.

I have run tyres narrower than the rim in the past but I don't really recommend that on leaning bikes. In this case, the question is for a trainer where leaning isn't an issue. The problem is that when you have (for example) a 45mm rim with a 25mm tyre extreme leaning can make the rim hit the road, at which point you will lose traction and crash. But this is an extreme problem, you're very unlikely to experience it in normal riding.

The increased pressure shouldn't be an issue unless you have exceptionally lightweight rims, but I'm guessing from the question that this isn't the case. If you do have a high-end carbon fibre mountain bike with ultralight, extra-wide carbon rims they should have the maximum rated tyre pressure printed on them or listed in their specifications. You should respect that. But that's not normally done for aluminium rims because the rim isn't the limiting factor for tyre pressure.

I've blown the sidewall off a rim, and running a narrow rim with wide, high pressure tyres was likely part of the cause for that. The manufacturer replaced the rim without questions, however, suggesting that they agreed that it was a weld fault at the join (where the blowout started). But you're not doing that, you're running a narrow high pressure tyre on a rim that is most likely capable of working with a wide, high pressure tyre. I would not worry about this, especially on a trainer where you're more likely to suffer hearing damage from a blowout than major crash injuries.

Going down by 0.85" without replacing the rim is generally discouraged, but since there are few road hazards on a trainer (those would threaten damage to the rim), this might be doable. Proceed with caution as the narrower tire will require significantly higher pressures and might not seat as well in the rim, heightening the risk of a blowout. If possible, I recommend getting a second rear wheel with a narrower rim and swapping entire wheels, which is significantly faster than replacing a tire.

Frame clearance and other similar constraints should not be a problem.


Replacing quick release wheel with ebike - motored wheel I intend to upgrade my FireFox Sniper V to electric, by replacing the front wheel with a motorised kit wheel.
My question is that the wheels (both) are quick-release: is it safe to motorise this bike.

! - the motorised kit wheel is bolt on type.

Yes, probably and maybe.   I'm unfamiliar with your bike model, but I have run my own ebike front motor for a couple years.

To answer your question - the old wheel is quick release, but the replacement one will likely be a bolt-on wheel.  It is possible to use quick release adapters, but wheel nuts are more secure and will hold the anti-spin washers better than a QR.

The main problems stem from design of the front forks and power of the motor.  As your motor powers on, the torque is transmitted through the axle.  Over time the dropouts get chewed out.

What is the wattage of your motor?   Anything under 300 watts doesn't have enough impulse power to cause a problem.  If you have over 500 Watts then a torque arm will help keep your forks working.

Here's an image of a torque arm - it helps distribute the rotational energy into the fork rather than just through the dropout.

Do you have disk brakes?  Your motor kit has to have bolt holes to support the rotor in the right place.   This is not an issue for rim brakes, but your rim brakes need to be working perfectly to cope with the extra speed and momentum.

Yes, it is safe, because motorized wheel will be firmly attached by the bolt mount.


Fitting a 9-speed 11-50T cassette on MTB: which derailleur? I'm trying to understand if its possible to fit a 9-speed 11-50T cassette (found one on Ali) on my MTB. The plan is to go 1×9. The problem is that I can't seem to understand the if a specific derailleur can handle that.

The rear derailleur in mind is Shimano M4000 long cage.
Should I use a hanger extension? Will 11-42T be better for that?

Thanks for the help

https://bike.shimano.com/en-EU/product/component/alivio-m4000/RD-M4000.html   says that derailleur will handle

Low sprocket_Max.    36T
Low sprocket_Min.    32T

ANSWER: You cannot run a 50 tooth cog with that derailleur.

You might be able to use a hanger extension, but that will make the small gears even worse.  Wolf Tooth's Roadlink allows up to 40 tooth, and Wolf Tooth's Tanpan says 44 or 45 tooth is the maximum cassette size supported.  Note these are for 10 and 11 speed.

If you're absolutely stuck on a 50 tooth rear cog, then you're looking at a SRAM 12 speed Eagle setup, which will not be cheap.  Cassette and shifter must change, and its very likely your freehub won't fit the cassette, and then the OLD will be too large to fit in your frame.  Not a good plan.

best way to go is to use sram 9v trigger (only sram) coupled with new generation clutch type derailleur - i use shimano slx 11v but also sram should go. Work like a charme with 9v cassette and chain, no adaptation needed.


Innertube fat on one side, skinny on the other I just bought a bicycle/bike tube (20"), when i inflate it, 1 side of it goes big/fat and the other just inflates normally, what should i do? , its happened with some of my other tubes.

You should mount the tire first and inflate second.

Tubes are not supposed to be inflated outside tires, they will behave like balloons but the material they are made of is not as stretchy.


How do I know if I can replace the 27 inch wheels with 700c wheels on my bike? I recently purchased an 80's Japanese bike off craigslist called "Jupiter King." It has 27 inch tires but I want to switch to 700c for greater wheel/tire selection. I specifically want some nice yellow wheels with yellow rim. Help? I am quite a noob with bikes. Thanks for any help/advice.

You may or may not be able to make that conversion with your existing brake/frame combination. Your brakes will have to reach farther because a 700c wheel is a smidge smaller than a 27 inch wheel. Depending on your setup, that may be possible. I'd recommend borrowing a 700c wheelset from someone to see if you can line it all up. If it all lines up, great. Purchase whatever 700c wheelset strikes your fancy. If not, you may be able to purchase brakes with a longer reach. Some older frames still won't work with 700c wheels even with the longest brakes available. If that's the case for your frame, you're stuck with 27's.

Personally, if it were me and I couldn't get it to work with the existing brakes, I'd stick with 27 inch wheels. If you start having to swap brakes out, it starts to get iffy and frankly, I think it's more hassle than it's worth. It's a lot easier (and maybe cheaper) to just start hunting for a frame that already has 700s on it.

The outside diameter of a 700 wheel is obviously (?) 700 mm which equates to 27.5 inches. A 27 inch wheel has an O/D of 27 inches. If things are a bit tight you cannot replace a 27 inch with a 700C especially if using larger sized tyres i.e. 38-700 or even 35-700, I know as I have recently tried it. You could probably get away with a small tyre such as 25- or 28-700 but may have to use longer brake arms. Better going the other way but not a lot of point, really.


Could I bike 9 mile a day home from work starting with no current exercise? I am thinking of getting a bike and biking it home from work on a mountain bike its 9 miles and reasonably flat, I'm not the fittest guy so I'm wondering if I would struggle??

I agree with the comments that 9 miles is a not a short ride for somebody not in shape, but you’ll get in shape for it really fast, so you should go for it. Just get ready to be sore in funny places for a couple weeks.

You can make your situation better by doing a few things:

Buy a road bike instead, assuming you’ll be on pavement. At the very least, replace your mountain tires with something smaller, in the 30–40mm range. Mountain tires will slow you down and make you work harder. So will a heavy steel bike.
Get a rack for your bike and buy panniers to haul your stuff. Wearing a backpack for 9 miles will get old fast. Whatever you do, don’t get one of those hip shoulder bags. Chiropractic disaster. Best is to get a bike with in-frame attachment points for the rack – many road bikes don't have these, so make sure to check before buying.
Get the bike and do weekend rides to get fit before using it for work.

Good luck, have fun, and be safe!

Is it there 9 miles and back 9 miles? Or is it 4.5 miles there and 4.5 miles back? The 4.5 miles won't be difficult. But the 9 miles, like the other posts say, might feel much in the beginning. But you will indeed get in good shape pretty fast if you do it consistently every day.

About the backpack topic, I disagree with the other posts. If you have a good backpack with a curved back, it won't be a problem.
I've got this backpack and use it on my 12 km (=7.5 miles) ride to work for 2 years now and it's an absolute delight. The "air comfort" system makes you sweat a lot less than a normal backpack (it's still a bit sweaty, but it's acceptable even on hot days), and the curved back makes it sit perfectly, so you barely notice it.
Panniers will changes the way your bike behaves: the balance and the mobility will be different. And if you enjoy the way your MTB rides, like me, you won't like it as much with panniers. But these things are of course personal taste.


Are modern clipless shoes and pedals that much better than toe clips and straps? I've recently returned to cycling after a couple of decades, and I'm trying to get familiar with the current gear and components.

I still use toe clips and straps on the pedals on my 1990 Trek road bike.  But clips and straps are so far out of fashion that you wouldn't even know that they used to be common.  I can hardly find a mention of them anywhere.

Why have the modern pedals and and shoes so completely replaced the old-style clips and straps?  Are they really that big an improvement?

Clipless pedals hold your feet more securely and release easier than toe-straps and clips. As you are probably aware, it is possible to to tighten straps to the point where they must be released before the foot can be removed from the pedal. A properly functioning clipless pedal will always release the riders foot.

Opinion:  Loved my Speedplays more than anything.  During a hiatus, my nueropathy kicked in but good.  I've gone back to toeclips feeling safer dismount, hopefully just until i can legs really suercharged back to past seasons ability.


Is riding shirtless safe? During the summer, I like to go for rides on trails without a shirt. Is this safe?

Also, related: is it rude to other people on the trail not to wear a shirt?

Safe is a relative term in this instance. A shirt might protect you in a fall, but only just. You'll know immediately whether a shirt can protect your skin from sticks, branches, and prickers dangling into the trail. If you were going fast enough flying insects may even make an impact, though I can't imagine it'd be terribly painful.

Shirts do offer some protection from two things: sunburns (and subsequent skin cancer) and bites from insects (potentially carrying disease.) For lightly complexioned people, skin cancer is a huge danger and can develop even without having been sunburned. Insect-borne diseases are also a big deal in most places. Having been treated for Lyme disease, I can attest to the importance of wearing insect repellent and, yes, shirts.

Additionally, that thin layer of material actually keeps you cooler by blocking the sun from reaching your skin - this is the same reason why desert dwelling peoples wear lightweight material all over their bodies. Having a shirt on also keeps you from sweating all over your bike and other gear.

In terms of etiquette: if you're out in the woods and there aren't many people around, go for it. If you're bumping elbows with people on a multi-use trail, maybe consider some modesty.

Go shirtless!
If you've got a great body, then seeing you will give someone a boost!
If you've a terrible body, the seeing you will give someone a laugh!
So, it's a winner either way...


Are today's bikes "better" than a few decades ago? I'm looking to buy a road bike for commuting. There is a guy near me who finds older road bikes (e.g. from the 80's) and fixes them up. Are there downsides to getting an older bike (assuming it's had a proper tune up) compared to getting a bike released in the last year?

The last major technological improvement in standard bicycles was indexed shifting.  The indexing part of this isn't that big a deal, but the feature also gives you the ability to shift under load (which is a big deal).  I'm thinking this change occurred in the late 80s, but my memory for chronology is poor.

Yes, since then we've gotten V-brakes, carbon frames, "compact" cranksets and a few other things, but they're not fundamental changes, just minor refinements (if that).

Re "non-standard" bikes, the biggest change has likely been the improvements in geared hubs.  These have gone from 3-speed, don't-dare-shift-under-load-or-you'll-wreck-it models to multi-speed or continuous models that encourage you to shift under load.

There has also been progress in recumbent technology, but I don't think there've been any game-changers (though I'm not up on this).

The main problem with a bike more than 15-20 years old is that replacement parts get harder to find.  In particular, if you buy an older bike you might want to buy a spare rear cluster right off, to have on hand.  And I wouldn't recommend buying a road bike with 27" tires, since replacement tires (of the narrow "racing" variety) will be hard to find.

I don't completely agree with some things that have been said here.

If you like old bikes, if you want it for the looks, go for it. It is a perfectly good reason, lots of people buy and maintain old bikes because they are classier and prettier. There is nothing wrong with it, your passion is perfectly respectable. I personally think something like this is absolutely gorgeous.

Just be careful when picking one, because age and rust attack the frame and components, so you should be careful that the frame is not too rusty if you want to recover it, and inspect the bike for cracks every week or so.

On the other hand, while it is (arguably) true there hasn't been a huge advance in bike mechanics in the last years, it is also true new advancements in materials, manufacturing techniques and mechanical principles make new components much better and durable.

I guarantee you a new, 2015 derailleur will last much longer than a new one made 25 years ago. It will because even though the mechanical principle is the same, a new derailleur has better bearings, better isolated, and the whole construction is more solid meaning there are less tolerances when it is shifting which will end up making it perform better and last longer.

This is true for all other components, but mainly for ones that have movement: hubs, headsets, cranks for example.

The better quality in modern products will also be more noticeable when you are using the bike, as it will feel more solid and flex less under hard pedaling, brakes will work better, wheel will flex much less, etc.

Of course if you compare an old Dura Ace derailleur (some of the best) with a super cheap one sent to you from China for $10 the old one might be better, but if you compare a 25 (from the 90's) year old Dura Ace with a modern Tiagra (some of the cheapest Shimano makes), I guarantee you the new one will perform much, much better. I have used them side by side and 25 years of evolution make a big, big difference.

Just look at them, old and new. See how different are the brakes for example? More material, less flex, better bearings, a mechanical principle revised for decades, all means they will last longer and perform much, much better.

As true for most things, using an older vehicle (car, motorcycle, boat, bicycle) means you will have necessarily less performance and more maintenance costs. I am not saying an older bike will make you go bankrupt, and it will last if you treat her well, but trust me, there will be a difference.

If nevertheless you want to go for the older one, I can't do anything else but pay you a nice, cold beer when I see you with it.


Is bicycle Helmet really effective? Sorry  I am new in bicycling , but I think  the head is least like to be in contact with any other things during crash normally down from head rather the head might come in contact in other vectors . So I am curious how effective bicycle helmates are .

Bicycle helmet is to protect the head, which has the most important organ in human. You could still live a normal life even with broken/ lost limb(s). But a head injury could change your life forever. A helmet is like a wall between life and death. The priority goes by protecting the most important thing to you first (i.e. your life), not by preventing the most common injury.

Having a priority list, you could fulfil the ' safety pyramid' for extra protection, e.g. helmet, arm/leg guard, gloves, boots. However, it is impractical to get a full body armour for just cycling. The risk of body injury that could lead to life and death situation whilst cycling is rather small. Thus, this is often ignored.

As Frisbee also mention, the brain is also a very sensitive organ. Yet, a seemingly  'minor' damage to the brain is often lethal. Therefore, the head needs protection, albeit a small possibility.

I have witnessed two head injury accidents (while cycling) in my life. One happened a few building block away from my house. It was a classic cornering accident type. The person lost balance (clipped the pavement), and hit her head directly to the pavement (no helmet). She unfortunately pronounced dead at the scene.

The second incident happened on the street. The person was riding in a freezing condition. It is with such unfortune that the person lost control on a straight road and hit his head on the raised curb. He is fiancé of my wife's friend. He is still in coma at this moment (since 3 years ago).

Needless to say, your argument is flawed. It is similar to a statement that: 'I have never been in an accident that an airbag is activated, so is airbag redundant?'

I think the head is least like to be in contact

It's true that there are many times I've fallen off without hitting my head ... especially at low speed.

I often put my hand on the ground -- and that's one reason why I like to wear padded/leather cycling gloves.

On the other hand if you do hit your head then a helmet can be helpful. One time I fell off (skidding on a corner with my feet clipped to the pedals) and I hit the ground before I knew it, and hit my head. Not wearing a helmet, that meant a trip to the hospital and several stitches (and a warning that I ought to use a helmet).

If you do hit your head without a helmet then a scalp wound with stitches might be the best that can happen (the worst might be concussion, brain injury, skull damage).


Can anyone tell me if this men or womens bike and possibly model? This bike is dirt cheap and fits my needs. I don't want to ask the seller too many questions and then discover the bike is worth more and not sell it. Im picking it up tomorrow for a steal. Question is this a girl bike and possibly does anyone know model outside scwhinn sierra? I cant find a similar picture of any bike so i cant I.D. any help would be appreciated.

I see "Schwinn Sierra" in the decals your photo.  I'd guess its somewhere between 2000 and 2010 in age.

As long as it works, stops safely, isn't going to fail, then its a good bike to ride.

Yes, it would be classed as a woman's frame, but there's no physical reason a male couldn't ride it as well.   It may have a female-specific saddle or might be slightly angled up at the front, but that's easy to change.

There's suspension, but its in the seatpost, and possibly some in the handlebar stem (or its an adjustable stem)   The saddle is also sprung.

The black bar is a carrying adaptor for a car rack, replicating the higher top-tube of a men's bike.  Its not part of the bike and probably shouldn't be there for riding because its clamped to part of the handlebars that should turn freely.

Schwinn marketted very similar bikes under the models "Quest" and "Mirada" (that mirada is older than the one in your question)

The picture is not great so can't really comment on the bike's condition.

A $10 bike that does its job is totally worth it.  By the looks, you get lights too, which would cost that by themselves.

seems like a womens bike,judging by the geometry- reeally low head tube.Plus the cushioned saddle.


Road 10 to 11 speed upgrade, what needs to change? Hope all is well.
Currently I have a Cervelo P2 2013 with an Ultegra 10 speed.
I would like to upgrade the drive train from the current 10 speed to an 11 speed setup (either the 105 or the Ultegra). The main question that I have is how do I know which bottom bracket do I need to get for the 11 speed setup to work correctly? Apparently it has a FSA Gossamer Mega Exo bottom bracket currently.
Is there anything else that I would need to consider besides the below:

cassette
derailleurs (front and back)
chain rings
chain
TT gear levers

The current brakes that are on the bike feel fine so I don't need to change those and I have 11 speed compatible rims (Campag Zonda's).
http://www.bikeroar.com/products/cervelo/p2-ultegra-2013/specs

I've done this conversion last year on my #2 bike from a 2013 Ultegra 10-speed to a 105 11-speed, to be able to use the 11-speed equipped wheels of a newer bike on my two bikes alternatively and avoid cassette swaps to do so.
The swapped parts are: the brifters, both derailleurs and the chain. The cassette of course! There is no need to replace the chainrings, the inner width of 10 and 11-speed chains being the same. It is only the outer width that changes because 11-speed has thinner plates. You could also keep the FD but I've chosen the new 105 FD. It is sleeker and easier to set-up and fine tune.
The quality of 105 from the most recent edition is far above Ultegra from '13, due to trickle down of technology. The most expensive part being the brifters.

The main question that I have is how do I know which bottom bracket do I need to get for the 11 speed setup to work correctly?

It depends on the crankset. If you use for example a Shimano Hollowtech II crankset, you need a Shimano Hollowtech II bottom bracket. There are quite many cranksets that work with 11speed setup. Thus, it's impossible to give a definite answer unless you have selected the crankset.
You mentioned considering chainrings. If I understand this correctly, you're not planning to change the crankset but rather only the chainrings. If this is the case, the existing crankset will work with the existing bottom bracket -- no need to change the BB.
Typically you would not need to consider the derailleurs (historically they had a standard cable pull ratio), but with the new high-speed setups each generation may change the cable pull ratio. Thus, unfortunately you may need to change the derailleurs as well. At least the rear one.
The rims have no compatibility with the drivetrain speed count. However, the rear hub does.
Anyway, I would suggest to reconsider the "upgrade". It's not a true upgrade in the sense that it would buy you much. It is debatable whether more or less speeds is better (I consider less speeds better because less speeds gives larger jumps between gears). If you for example have 11-30T 10speed cassette, it has 11.79% jumps between gears. A 11-30T 11speed cassette would have 10.55% jumps between gears. Hardly a large improvement. And I would consider this a step backwards rather than a step forwards as I prefer large jumps between gears.
Newer chains seem to be more durable than older chains due to improved materials and manufacturing processes, but it is a good question whether the increased durability of newer chains offsets increased price of the newer chains. Also, the "upgrade" from 10 speeds to 11 speeds costs so much that you're unlikely to ever recoup the investment in saved chainwear costs.


Sunglasses for commuting? I've recently started commuting via bike to work (6.5mi each way), and am looking for advice on gear... specifically sunglasses (which I find useful to prevent dust in eyes and to help block the ample sun).

Currently I'm using an expensive pair of Oakleys (not meant for riding per-se), but I'm wondering if I should get a specific pair of glasses that are preferred by riders.

Any suggestions on brands or even specific models would be nice.

If you don't want to spend lots of money you can still get the most relevant characteristics in a pair of safety glasses.

You can find these at just about any hardware store and they:

wrap around,
are impact resistant,
block UV,
don't look half bad
come in clear and tinted (and are cheap enough to get one of each usually)

Yes! Cycling-specific sunglasses are super important. You need frames that stay on your face when you’re in the cycling position so you don’t have to look over the top of your glasses when you’re hunched forward. They also need to be compatible with your helmet as well as have rubber temples and nose grips to prevent them from slipping. Oakley and Rudy Project are two brands that make great cycling glasses.


Stainless steel bolts for brake calipers I'm wanting to replace the bolts used to hold my cantilever brakes on as they've rusted and look pretty terrible on an otherwise clean bike. Is it ok to use stainless (A2-70 or A4-70) for these or would I be better with mild steel and replacement more often?
I'm less concerned about the rear as the braking force pushes the calipers into the frame, but if a bolt head breaks off on the front under braking it would turn fairly ugly.

The braking loads are unlikely to be enough to exceed the tensile strength of a 6 mm bolt – forgive my butchering of units here, but it would take something like 2,250 pounds of force to make a 6 mm bolt fail (75,000 psi tensile strength for type 18-8 or 316 stainless and about 0.03 square inches in the bolt works out to around 2,250 pounds of force). That's load at failure, but it seems like the limiting load on the brakes will be about the weight of the bike and rider. That means that even a big rider on a heavy touring bike isn't capable of much more than about 400 pounds of load. I found my data here.

So structurally, I think you're sound. You can have a pretty bike.

I got stainless bolts all over my bike. Like DLU said, they will be strong enough to handle forces on the bike. I like to get my screws in small amount (saves me space in my "hardware" drawer) from this place online


Safety data: Which is safer, head/tail lights which blink or emit a steady beam? My head and tail lights can be set to blink or emit a steady beam of light.

I usually set my rear (red) light to blink, because I believe it makes me more visible at night. My friend argues that it makes it more difficult for motorists to judge how far away I am.

Are there any studies showing which is the safer way to use a tail light?

The short answer is that 'safer' is subjective and depends on your requirements.

You are both correct.  Movement attracts the eye, so your blinking light is noticed.  It is easier to judge the position of a steady state light.

For a motorist to pick out your tail light, particularly, from a sea of noise is very difficult.  The surface area of the light is tiny, and it's all on its own.  Your light is just not important enough to notice amongst the jumble of signs, traffic directions and other cars unless it does something to stand out, like flash.

My understanding is that the reason it's easy to see cars (apart from bulk) is that they have 2 lights moving together.  Something to do with your brain automagically resolving the connected pattern.  That's why it's hard to see a car with one working taillight, or a motorcycle or bicycle.

In terms of safety, my policy is always 'be seen and misjudged' rather than 'not seen'. So I always set both front and rear lights to blink at night.  If you need illumination for the road, I'd strongly suggest a second forward light for that.

From Rear Lighting Configurations for Winter Maintenance Vehicles

  Flashing lights will be perceived as having higher brightness than steady-burning lights, up to a flash frequency of about 15 flashes per second. Such brightness enhancement can aid in conspicuity, and several rear lighting systems have been designed to have a flash rate between 5 and 9 flashes per second in order to maximize their perceived brightness. While conspicuity may be greater with such configurations, an observer’s ability to make accurate judgements of relative speed or distance may be compromised when flashing or strobing lights are used. Croft observed that the judgments required in tracking an object were difficult to make under strobing conditions, yet very easy in steady-lighting conditions. Observations made during a study of service vehicle lighting for maintenance operations similarly pointed out that strobing and flashing systems designed for maximum conspicuity can at the same time reduce one's ability to judge relative speed and distance. Periodic sampling of the field of view in another study resulted in deterioration of one's motion-tracking ability that increased as the distance to the object of interest decreased.

Also from Selection and Application of Warning Lights on Roadway Operations Equipment

  Flashes are bursts of light which, by definition, are unexpected
  because they do not occur in nature (save for lightning).
  This characteristic is their most important feature and
  why they are so good at capturing attention.

No data points, but I would agree that in most cases the flashing light is better.  A single, constant-burning light can easily get buried in "noise", and there's even a tendency for motorists to unconsciously follow a constantly-burning moving light ahead (especially if drunk), a fact that I suspect figured into a couple of nighttime rear-end collisions I've learned of over the years.

To improve the ability of the motorist to judge the location and speed of the light it's better if it flashes relatively rapidly -- maybe 2-3 times per second.

Re legality, 169.222 subdivision 6 of the Minnesota statutes states:

  A bicycle may be equipped with a rear lamp that emits a red flashing
  signal.
  https://www.revisor.leg.state.mn.us/statutes/?id=169.222


What is the effect of adding weight to a wheel vs adding it to the frame? There are claims often made that, eg, "An ounce of weight at the rims is like adding 7 ounces of frame weight." This is "common knowledge", but a few of us are skeptical, and our crude attempts at working out the math seem to support that skepticism.

So, let's assume a standard 700C bicycle tire, which has an outside radius of about 36cm, a bike weighing 90Kg with bike and rider, and a tire+tube+rim weighting 950g. With the simplifying assumption that all the wheel mass is at the outer diameter, how much effect does adding a gram of additional weight at the outer diameter have on acceleration, vs adding a gram of weight to the frame+rider?

I asked this question over in the physics Stack Exchange.

The answer I got was 2x -- adding one ounce (or gram) to the wheel at the outer diameter (ie, the tread) is equivalent, in terms of force/energy needed to accelerate, to adding twice that amount to the bike frame.

The answer was a bit involved and takes careful reading to fully understand, but the answer can also be explained with this thought experiment:

If you have a theoretical weightless wheel, fixed to a stationary axle (ie, not rolling on the ground), and you add a mass to its outer diameter, the energy needed to accelerate that added mass to some tangential velocity is the same as the energy that would be needed to accelerate the mass to the same linear velocity (ie, as if it were attached to a weightless bike frame).

But if our theoretical weightless wheel is not fixed on a stationary axle, but is instead attached to our theoretical weightless bike, we are accelerating the mass both tangentially AND linearly so we add the two energy requirements together, meaning it takes 2x the force to achieve the same acceleration and 2x the energy to accelerate to a given speed.

So the answer is 2x (and not 7x or 10x or whatever is often quoted).

So, it is well known in physics that a solid disc (weight evenly distributed) beats a hoop (weight evenly distributed on the periphery)  and a sphere (weight distributed evenly) beats both a disc and a hoop when rolled down a plane using nothing but gravity. It all comes down to the weights distance from the axis. At the beginning it takes more energy to move a specific weight or when going up hill. But if a flywheel is used that is potential energy and the heavier the flywheel the more energy will be stored in the rotation. But like a Yoyo it's not a 100% return. It will however help you up the next hill if a constant rotation speed is maintained until needed. Have you ever coasted down one hill and didn't have to pedal again until about halfway up the next? Ya, that's it.
If you are 120lbs and your bike is 10lbs plus you add a 60lb flywheel and you can get the flywheel up to say 1,000 rpms it will probably carry you up a pretty big hill. Let's get that guy Colin from YouTube to build a contraption to figure this out. (He built mag shoes to walk on the ceiling)


How can I get rid of I.T. Band pain caused by cycling? I have struggled for a while with Illiotibial Band pain or Illiotibial Band Friction Syndrome when cycling and running, here are some of the things that I have done to get rid of the pain:

When it is inflammed:

Cataflam (a non-steroidal anti-inflammatory - NSAID)
Ice
Transact patches (topical anti-inflammatory)
Rest

Prevention:

Hamstring strectches
Massage (cross friction on ITB)
Strengthening of gluteus medius
Stretching of gluteus medius and TFL (Tensor Fascia Latae)
Foam roller
Bike setup correction (moving saddle forward worked for me)

There are some good resources on the Internet, here are some I have read:

Cycling Problems - ITB Pain And Tightness, by Karen Doyle

ITBS Help Site

What have you done to get rid of ITBS?

Not sure if my direct pain was related to ITBS - but this cut out a lot of pain I was having: Custom Pedal Extenders.  I am large person and this reduced a lot of pain I was getting in my inner thighs and hip.

The most comprehensive article I ever read. Yeah, you have to pay for it and it doesn't have a silver bullet, but it's for sure bring some light on this topic. Since I've tried everything except of surgery, I am still experimenting of different treatments. Last year it just disappeared after 4 months, I tried to stop riding for several month, then I got tired of not riding and went back to it and after several weeks pain disappeared. Now it came back...

So in particular, I've tried:

icing (several times a day)
foam roling
stretching
stopping riding
reducing intensity of the rides
reducing time of rides
iboprofen
physical therapy
hips exercises
core exercises
microcurrent therapy
contrasting (ice + heat)
self massage
seeing massage therapist
taping
eating a lot of anti-inflammatory food

It disappeared magically, so can't say what worked if anything.


changing disc brake pad material while keeping same rotors I would like to know what effect changing the material of a set of disc brake pads would have on the rotors if you kept them the same. for example, If I have resin pads and have been using them for the life of the rotors, what would happen if I switched to metal or organic pads, while still keeping the rotors the same? Would they just squeal like crazy?
thanks

Just called Shimano to ask this question for a customer's bike. For switching from a resin to a metallic padset, the answer is clean rotor with isopropyl alcohol and do a standard bed-in.

Didn't ask them about metallic to resin

Depends on a lot of factors such as the rotor and pad make etc. The rotor has memory, left from the remains of pad material over time. What you can do is sand down the rotor surface lightly with medium grade sandpaper and then bed in the new pads as per the manufacturers instructions. Usually 10-20 hard stops without skidding. This will help avoid squealing etc as much as possible.