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Brake Wear on Sidewall

Old 09-15-18, 05:30 PM
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Brake Wear on Sidewall

I was setting up a new bike and misadjusted the rear rim brakes like an idiot. The shoes were rubbing the very edge of the tire sidewall for ten miles before I noticed— but not before they carved a nice indent about 1mm deep along the edge of the sidewall.

Obvioulsly I fixed the brake shoe alignment as soon as I noticed, but now I’m worried the tire is shot. Am I worrying over nothing or should I replace? There are no threads showing through.
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Old 09-15-18, 08:16 PM
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The fabric is what gives the tire its strength so if that is undamaged you should be OK. Keep an eye on the pads, since the geometry of the brake may move their position slightly as they wear, and you don't want it hitting the tire again.
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Old 09-16-18, 06:21 AM
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I can't say without seeing it but it doesn't take very long for brakes to completely wear through a tire sidewall and cause a blow out. If it was my bike I'd replace the tire and chalk the cost up as tuition in the college of bike mechanics.
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Old 09-16-18, 06:56 AM
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Originally Posted by Retro Grouch
I can't say without seeing it but it doesn't take very long for brakes to completely wear through a tire sidewall and cause a blow out. If it was my bike I'd replace the tire and chalk the cost up as tuition in the college of bike mechanics.
That sounds like a very sensible thing to do, contrary to your signature line (which is the best I've seen in a while).
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Old 09-16-18, 07:07 AM
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Your brake pads were probably properly installed. The problem is with brake arms that pivot from the side, like center pulls or one of the dual pivot brake arms. The arm movement is both towards the rim (lateral) and upwards. That's the nature of the pivot. The brakes pads will move progressively further upward, as the pads wear. Unless, the pad position is monitored, pad wear can progress so that the top of the pad will mate with the tire sidewall rather than the rim.

There's a reverse wear problem with side pivot arms that move downward like linear and cantilever brakes. Eventually, the bottom of the pad will miss the rim surface. This will result in step wear of the pad. Only the top of the pad will perform braking and show the wear. The pad bottom will remain untouched, having missed the rim. Sometimes this step will cause the brake pad to jam on the rim and return slowly or not at all.

If you want to avoid this problem and don't want to be bothered to inspect your bike, get brakes whose arm pivots from a point that's directly above the tire center. This is true for one of the dual pivot brake arms and completely true for side pull brakes.
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Old 09-16-18, 08:26 AM
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Originally Posted by andrewclaus
That sounds like a very sensible thing to do, contrary to your signature line (which is the best I've seen in a while).
Thanks.

The best part is, regardless of whatever silly stories they remember, I can die happy knowing there are that many more that I've gotten away with and nobody knows about.
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Old 09-16-18, 10:44 AM
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U brakes on underside of chainstays were Easy to ignore the Pad wear,,

and as the pad wears the contact patch gets closer to the pivot.

with U brakes that is off the rim into the sidewall

Cantilever/V brakes thats off the rim into air ... , until off rim into spokes..

Linear motion , Shimano's Parallel push , and Magura Hydrostop (HS 11,22,33)
do tend to stay in contact with the rim as the pad wears Thinner..



..
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