Bending your brake rotor?

Went on a great ride in Gunnison over the long weekend...Hartman Rocks area is well worth a stop if you are ever in the area with a bike...but the downside is that i somehow sustained a bent rear brake rotor. I did not crash or take any flying rock shrapnel at any specific point I can remember, so am not really sure how this damage was sustained. Rear wheel does not spin through entire rotation freely and I had to loosen the brake calipers until the rear brake lever must be pulled all the way to the handlebar to engage...not that sweet.

So, I have two questoins for mechanically knoweldgeable peeps. This is my second disc brake ride, but curious to know if there is some aspect of my riding that might have contributed to bending the rotor? Besides crashing. I am riding Avid BB7 mechanical discs if that helps.

Second, what is the process for fixing? Can I (or shop) bend a rotor back to true like with a wheel that has gone out of whack? Or do you have to buy a new one?

Put your bike in a repair stand.

Spin wheel.

Determine where the rotor is out of true.

Take an adjustable (crescent) wrench and close it so it's as wide as the thickness of the rotor.

Bend the rotor back to true.

get a small crescent wrench and just bend it back

Edit: right, what homer said, albeit faster than me.

You most likely hit it on something without realizing it...welcome to the fun and exciting world of disk brakes.

Just take a crescent wrench to it bit-by-bit. You should be able to get it straight enough to be rideable. You'll never get it perfect, but you can get it to the point where it's not noticeable and doesn't rub.

If I bought a new rotor every time I bent one, I'd be a poor man.

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Originally Posted by pde20

Went on a great ride in Gunnison over the long weekend...Hartman Rocks area is well worth a stop if you are ever in the area with a bike...but the downside is that i somehow sustained a bent rear brake rotor. I did not crash or take any flying rock shrapnel at any specific point I can remember, so am not really sure how this damage was sustained. Rear wheel does not spin through entire rotation freely and I had to loosen the brake calipers until the rear brake lever must be pulled all the way to the handlebar to engage...not that sweet.

So, I have two questoins for mechanically knoweldgeable peeps. This is my second disc brake ride, but curious to know if there is some aspect of my riding that might have contributed to bending the rotor? Besides crashing. I am riding Avid BB7 mechanical discs if that helps.

Second, what is the process for fixing? Can I (or shop) bend a rotor back to true like with a wheel that has gone out of whack? Or do you have to buy a new one?

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on a long steep descent the rotor heats up to the point where it can warp. Try removing the rotor and heat it with a propane torch. Lay it on a flat surface and bang it with a mallet. if that doesn't work, throw down $10 for a new rotor.

thanks all....good to know this is as common as a flat and just as fixable.

Quote:

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Originally Posted by powder11

on a long steep descent the rotor heats up to the point where it can warp. Try removing the rotor and heat it with a propane torch. Lay it on a flat surface and bang it with a mallet. if that doesn't work, throw down $10 for a new rotor.

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There was an interesting thread about this on Ridemonkey. What it came down to was the fact that in order for the metal to be maliable, it has to reach a temperature that is high enough to reduce the integrity of the metal, effectively making it brittle. Just something to consider.

use 3 wrenches so you don't just warp it even more.

two to hold it steady and one in the middle pulling the out of true section back to true.

requires both hands and careful bending

What they said, but make sure to clean it with rubbing alcohol after putting your slimeball hands all over it.