Originally Posted by
drbenjamin
Since we're covering a lot of topics on BB7s I've got a question for the crowd:I commute year round in Seattle, and put a cyclocross fork w/ BB7s on my road bike. Huge improvement in the winter, it's really no contest. My rims get covered with a fine abrasive paste, and while I can scrub it off by tapping a rim brake repeatedly sometimes I need my brakes NOW not in 20 sec.Anyway, today we had a rare sunny day. I went for a ride and was coming down a 1200 foot hill with grades 14-20%. The brakes felt fine the whole time, but 2/3 way down I got nervous, pulled over and sprayed a little water on the (stock) disc. The water instantly turned to steam. So my question is, how much heat can these things take? Do they fail catastrophically or do you get some warning? It would have really sucked to lose brakes on this descent.
They can fail if you're a complete bozo. Read
this for a description of what that's like. The failure described at that link may be hydraulic-specific.
You're actually in the ideal setup, because you can use your rear brake to scrub speed on descents (which is safer anyway), while saving the front brake for actually stopping. Someone will immediately jump in to lecture me about why using the rear brake in this way is wrong, but I think on a long, steep descent with a front disc brake it makes sense. Of course, with enough abuse on a descent you can get a rim brake to fail too. On the other hand, who needs to slow down.
