It has already been established that most of braking power comes from front brake. Now, several times that I have been replacing brake pads on my commuter cyclocross bike I have noticed that rear pads are worn out but front still have some rubber in them. Does this happen to anyone else, and why would this happen? The brakes are Shimano cantilevers, previously I had no-brand min-V's that did the same.
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Are you riding in conditions where you use the rear brake a lot more than the front brake (e.g. snow)?– BatmanCommented Sep 12, 2015 at 16:29
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1I changed the title slightly as this is specific to the OP.– RoboKarenCommented Sep 12, 2015 at 16:40
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@Batman not really, just some wet gravel paths. Chris H's answer seems sensible to me.– ojsCommented Sep 12, 2015 at 17:07
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Most of the braking power comes from the wheel where you do most of the braking. This rule is only broken if a tire is skidding rather than maintaining solid contact with the road.– Daniel R HicksCommented Sep 12, 2015 at 18:12
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...and, given that the cyclist does know what they are doing and not counting some special situations, it is the front brake.– ojsCommented Sep 12, 2015 at 18:14
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4 Answers
There are a couple of factors that might come into play.
The first is that you may be braking more than you think at the back. Which brake is controlled by your stronger hand? Are they adjusted the same?
The second factor is dirt. The front wheel throws up dust and muddy water, some of which can reach the back wheel even with mudguards. This can abrade both the pads and the rims. This will be much reduced on disk brakes.
If you use the brakes a lot downhill you may find yourself using the back lightly to stop yourself accelerating. This seems to cause quite a lot of wear, perhaps because the brakes don't remove the dirt like they would in a hard stop and perhaps because it's a lot of wheel revs with the brake touching the rims.
I used to notice this on stock pads and the cheap dual compounds I first replaced them with. The KoolStop pads I now use wear much less and I don't notice a difference. This is on ordinary shimano V brakes. This was despite only taking up the slack in the back brake when coming to a hard stop, but I had a couple of steep downhills.
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1I would add that the use of the rear brake to slow down (in any situation) wears down the pad faster than using the front to stop since it will rub longer on the rim.– BibzCommented Sep 12, 2015 at 19:11
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@Bibz that's a good point, though it's also used with lower contact pressure which will go some way to offsetting the extra wear. I'm sure wear vs. pressure isn't linear; wear vs. total distance moved over the surface probably is.– Chris HCommented Sep 12, 2015 at 19:46
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1ChrisH very much so. Minimal contact is basically sanding the pad down, and the rest I agree with @Bibz. Plus if there's grit you can also be sanding the rim down... I killed a front rim touring once using rim brakes on a rainy day down a long gravel descent. Just enough muck in the water to help the brakes abrade the rim. Made it home, but not by much.– MóżCommented Sep 13, 2015 at 4:26
Generally, front will wear faster, for both the rim and the pads. Bicycle is a bit hard to judge because it depends on the rider's habit, brake pad's quality and surface contact, and also the rim's quality.
I can tell you that front brakes in cars need replacing more often than rear. This example is a bit more objective than bicycle since front and rear are operated by a single brake (although it depends on how the brake is setup and is still subjective).
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I've never seen a bike with a single brake lever that actuates both front and rear. What country are you in?– Criggie ♦Commented Sep 13, 2015 at 22:35
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Hi Criggie, I was talking about car on the second paragraph. It is n example of how front brake wears out much faster than rear, especially on old car.– Nhân LêCommented Sep 13, 2015 at 22:40
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Cars generally have dual circuit brakes, so one pedal runs two distinct braking systems. There's a bias as well so that more of a car's braking effort is sent to the front circuit. However this is getting really off the subject of a cable-actuated bike brake wearing its pads.– Criggie ♦Commented Sep 13, 2015 at 23:03
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I dont agree, if it's new car that has bias, they usually has bigger pad and rotor as well. As you said I agree it's off topic. But I want to demonstrate that on old car, where brake and clutch still operates with cable, front wears out much faster– Nhân LêCommented Sep 13, 2015 at 23:09
It is due to the extra weight on the back wheel. The back wheel feels a higher torque due to the higher ground friction (due to the higher normal force from the ground). Hence it takes greater brake torque to stop it.
Note that the ground friction wants to keep turning the wheel over! Opposing torque is provided mainly by the brakes and a little bit by the normal force because the tire is a little flat where it touches the ground. The more you inflate the tire the less it deforms and minimizes the stopping torque from the normal force. That's why the bike rolls better with more inflation.
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1Hi, welcome to bicycles. You actually have multiple counter-factual statements here; can you provide any evidence for this?– DavidWCommented Aug 15, 2022 at 17:06
Because there is more weight on the rear because that's where you are.
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4Nope - that's tyre/tire wear. Question is specific to brake pad wear.– Criggie ♦Commented Dec 2, 2017 at 9:43
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1We're generally looking for answers that give a decent amount of detail. I don't, personally, see how there being more weight on the rear would lead to brake pads wearing faster -- I could certainly be wrong, so could you explain why it works that way. In particular, most of the braking force comes from the front, as weight shifts forwards when you brake. Commented Dec 4, 2017 at 14:00