Join Date: Aug 2006
Location: Ann Arbor, MI
Bikes: Trek 7200 FX ('05), Trek 6000 ('07)
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Disk brake grief
Problem: Disk brakes offering near-zero stopping force
Examination: I've had my disks (avid bb5s) for a while. They've never really stopped as well as some other disk equipped bikes I've ridden (I've ridden other bikes with bb5s and I think maguras as well) but they've done enough in the rain and dirty to justify their not so goodness with stopping when it is dry out. Lately I've had issues with the stopping power getting less and less. I've always been careful never to get oils on the rotors or pads. Eventually I got really upset with the fact that I can stop as fast on my road bike with sucky calipers as I could with my disks so I took the pads out and cleaned them.
Cleaning process: Soaked for 5 or so seconds in rubbing alcohol, dried with paper towel and rubbed the surface with semi coarse sandpaper. Didn't touch the pads with my fingers or any source of oil at all.
Result: Since the cleaning, I've lost all braking power. Literally from about 1 mph (according to my cyclocomputer) the rear brake engaged AS HARD AS POSSIBLE will stop me in about two and a half feet. The front brake will stop me in about a foot and a half. From less than 1 mph (too slow for my computer to pick up) the rear brake stopped me in about a foot and a half. Front in about a foot.
So I rode the bike in a sandbox since I've heard that braking power is reduced after initial cleaning and only is restored after "grit" has settled into the pads. I even kind of threw some sandy mud onto the rotors and rode another few hundred meters stop go stop go (mind you that the stop motion would take up to 10 feet if I was going anything more than 2mph...).
I'm completely out of ideas - what has happened to my brakes?