Recently went on a 5 day trip with 8 other guys. During a hot day, mountain ride with a ton of speed bumps 2 KTMs and a Harley lost their rear brakes. Letting them cool down and it was pretty much alright again. I never lost my brakes although after the trip I noticed a brownish discolorazation on the front brake disc running down the center of the disc. Never had that bhappen before. Common?