Disappearing/re-appearing rear brake - stumped.
Put about 250 miles on my 2009 garage queen today.
She's only got ~4K miles on her and, for the first time, got her dirty and hit some gnarly fire roads in the hills.
I experienced a problem with the rear brakes that I am stumped about: While riding on the fire road, at one point the rear brake was working fine. I remember because I locked up the rear wheel for a sec on a tricky descent.
Just seconds later the brake pedal went completely down as if there was no pressure. I thought for sure a rock had hit the master cyl. I tried pumping the pedal and could not get any pressure back.
My riding buddy was ahead so didn't bother stopping to inspect, just kept on going. Ten minutes later, the rear brake had pressure again. "How freaking odd," I thought to myself.
I caught up with my riding partner and we stopped and looked at the bike. The line was fine, brake fluid level was fine, caliper was fine, pedal was still in place. Other than being dusty, everything looked in order.
This happened three more times while riding off road. Rear brake would disappear, no pressure, then 5-10 minutes later mysteriously start working again.
During the remaining 2 hours home on the twisties and then the slab no more problems. Rear brake works fine sitting in the garage right now. Plenty of pressure.
I am completely flummoxed as to what could be causing this. I've never even had the rear wheel off the bike yet. Any ideas?