Troubleshooting Disc Brake Failure
This past weekend while guiding at Mountain Bike Oregon (MBO), my rear disc brake was failing. I run Avid BB7’s which was stumping most everyone because BB7’s are pretty darn reliable.
I noticed the failure starting to happen on my first run down Alpine on Friday afternoon. On Saturday morning I decided it was probably time to change the pads. I did so even though the existing pads still had a little bit of life left. Took it for a short ride on Salmon Creek to break in the new pads and now my stopping power was even worse. I got back and asked around and one mechanic suggest I clean the rotor with rubbing alcohol, tried that and nothing. Others said I probably just needed to brake them in more on a good downhill. I finally asked one of my fellow guides, Tori from Gracie’s Wrench, explained what was happening and what I’ve done so far. Tori said the only thing she could conclude was a contaminated rotor.
So how does one contaminate a rotor? Brake rotors are made with a very porous metal and absorb oils very easily. It’s likely that I may have gotten over spray on it while lubing my chain. Even the oils from our fingers can contaminate a brake rotor.
Fortunately for me I was at MBO with industry vendors galore and a big thanks to Mike from Titus (you have a six pack coming at August MBO) for kicking me a 160mm Avid rotor that he happened to have laying around. I replaced the rotor, took some sand paper and cleaned up those new brake pads. Considering all I had done at this point, I figured I might as well recable the rear brake too.
About 1 minute into the first DH I had all the stopping power I needed for another great bombing down Alpine Trail in Oakridge. I’m pretty sure Tori was right about the contaminated rotor because having new pads and knowing the brake cable wasn’t that old… what else is left?