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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 02-21-06, 10:41 AM   #1
MarkS
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Can brake overheating occur on hills

I had hear that tire overheating occurs on mountains, but didn't know it could happen on hills.

I was going down one of the steepest hills around here on my mostly-road bike. Just coming out of a cold, and not feeling physically brave, I pretty much rode my front brake down. The hill is very steep, and I was still going about 15 even with the brake. Its about a quarter mile down the hill. Just as I got to the bottom and was lining up with traffic, my front tire flatted.

I didn't find any debris in the tire, and I replaced the tube. When I got home I opened it up. The plastic rim strip had little depressions at each spoke well. On one of them (presumably the one that caused the flat), the rim strip had broken through.

So, my questions are: Can I short but steep hill cause enough heating to overheat a tire/tube? And, would it help to use cloth rim strips?
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Old 02-21-06, 10:44 AM   #2
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I really dont like those cheap rubber or plastic rim strips. They dont stay put, and can break.
Velox is all i will use, its 5 bucks per roll and will last forever.
I dont think a short steep hill will cause overheating. Rim brakes generate very little heat.
Get some velox and try that hill again
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Old 02-21-06, 11:04 AM   #3
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I have generated enough heat on a long descent to burn my hand on the rim. Tandems are notorious for overheating, hence the additional hub drag brake.
You can reduce heating by feathering the brakes and alternating front and rear.
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Old 02-21-06, 11:05 AM   #4
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It dosen't sound like overheating caused the flat. It sounds like you had a bad rim strip.

Don't forget that your bike has TWO brakes. The rear is espcially good for scrubbing off speed on a downhill. You then have a front brake that is still cool to help you stop. The way brakes work is that they convert the rotational energy into heat. Learn to use both of them together.

I have had my rims so hot that you can't touch them many times, and still have never had a heat related flat.

I like cloth a lot better than rubber. I have to use the hard plastic ones with my Cosmos wheels. The Velox ones just don't work on them. Maybe that's why Mavic gives them to you woth the rims?
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Old 02-21-06, 11:24 AM   #5
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If you go down the hill as fast as you can but sat up so you have the most air drag, most of the potential energy you have will be dissipated in the air. Applying the brakes in short hard bursts will cause rapid temperature rise in the rims which will tranfer to the air before it heats the tire too much. Going down a hill using the brakes all the way to keep your speed down, will cook the tires.
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