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How much punishment can rim brakes stand?

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How much punishment can rim brakes stand?

Old 09-03-07, 04:54 AM
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joe99
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How much punishment can rim brakes stand?

How much punishment can rim brakes stand?

On a long descent (for example a total drop of 140metres), what is the first sign of trouble?

Do you expect to smell burning, see smoke or what?

Or do you first notice "brake fade" - i.e. greater pressure on lever having less effect? (I guess there is probably a whole generation of young drivers who have never even heard the term "brake fade" in connection with motor cars.)

As background info, my bike has a back pedal brake which I hardly ever use. Judging by the size of the brake drum, part of Nexus 7 speed hub, I would not expect it to be able to contribute much on a long descent as it does not look as if it could dissipate much heat.
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Old 09-03-07, 06:42 AM
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Front brake is the primary one. I have experienced brake fade on long downhills before. The best bet is to use both brakes alternately to give them a chance to cool. Don't ride them all the way down. If I did a massive amount of mountain riding I would seriously consider an upgrade to a disc brake on the front. However I have done just fine with rim brakes for 35+ years

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Old 09-03-07, 07:51 PM
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on a loooooooooooooooooooooooooooooooooooooooooooooooooong downhill dragging the brakes a lot,
2 things can happen

tire blows from the heat
pads melt

if you don't experience these things then it's all good
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Old 09-03-07, 09:59 PM
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And if you do, you're in deep crap
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Old 09-03-07, 10:49 PM
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Punishment? What did they do wrong?

I say timeout corner. For fifteen minutes.
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Old 09-04-07, 05:07 AM
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Spare the rod & spoil the brake pad!
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Old 09-04-07, 05:27 AM
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Rather than riding the brakes all the way down, I would divide the descend into 3-4 sections of hard braking to give the brakes time to cool down in between.
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Old 09-04-07, 11:10 AM
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If you're worried about it, I'd test it out. Find a nice warm day, and ride down that hill. Just stop every few minutes, and put your hand onto the brake surfaces. I don't know what kind of temp limits there are, but if you can hold your hand there, then you should be safe. Repeat a few times. Oh: don't just grab the surface, put your hand close first, just in case it's actually boiling hot.
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Old 09-04-07, 02:57 PM
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Yeah, I was wondering this myself. There's a long steep grade that I ride, 13 - 14%, and I have to use heavy braking to keep my speed down to stay in the "swept" track on the curves. I was wondering how much abuse this was doing to my brakes and rims.
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Old 09-04-07, 03:06 PM
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Originally Posted by slvoid View Post
Rather than riding the brakes all the way down, I would divide the descend into 3-4 sections of hard braking to give the brakes time to cool down in between.
Exactly as we do on the Tandem- Works on or offroad and gets you down safely. We have Discs on the Tandem but so do most tandems. On the MTB it is only brake when things get blurry and On the road it is back to the Hard brake and then off system.

Problem with rim brakes is the wear taking place on the rim. The Braking area should be completely flat and no deep scores. As soon as the rim goes concave- Time to rerim or get a new set of wheels.
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Old 09-04-07, 04:13 PM
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Lots of good info... but I am still wondering about my original question as to what signs of trouble are generally the first to occur. Hopefully the first sign is not waking up in a ditch!
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Old 09-04-07, 07:30 PM
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You can try stopping once in a while and touching your rims with your hands to see how hot they are. If they are getting too hot, you can rest a while and let them cool. This has worked for me.

['Too hot' is when they seem too hot to the touch -- I wish I could give a more precise answer; maybe someone else can?]
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Old 09-04-07, 08:24 PM
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Depending upon the qaulity of your brake pads and brakes the first sign may be fade, it may be the smell of burning rubber, it may be grinding, and it may be when your tire explodes.

Not all brakes, brake pads, and rims are created equal.
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Old 09-05-07, 09:13 AM
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Originally Posted by Stacey View Post
Spare the rod & spoil the brake pad!
i think bonus points are in order for the "rod (stirrup) brake" reference...
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Old 09-05-07, 09:52 AM
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A classic mountain driving tip for automobiles and trucks:

1. Establish your maximum safe speed.

2. When you reach this speed, slow between 5-10 mph and let off the brakes.

3. When you reach maximum safe speed, apply the brakes to slow 5-10 mph.

4. Repeat.

On a bicycle, you can alternate between front and back brakes, to give each a longer time to cool.

As for signs of impending brake failure, I'm not sure. Doesn't your infrared rim temperature gauge give you a warning?



I guess my point is that if you use the correct braking practices, you will never get into trouble from overheated brakes or rims.

It would be a neat research project to find out the limits of downhill braking, though. Wear your helmet.
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