Originally Posted by
bikenh
The thing I really wish I knew was how much heat is too much heat. I do have metal rims versus carbon rims so that does help me a bit.
IIRC: heat build-up is maximized when you hold your speed to 1/2 of the air-drag limited terminal velocity. That is, if you let the bike coast to its maximum speed, "feathering" the brakes to half that speed will put the most heat into the brakes.
This is a problem velomobiles (streamlined enclosed recumbents) encounter. They can descend so fast, they quickly overwhelm most bicycle brakes. They tend to pulse their brakes: slow almost to nothing, then let gravity accelerate them to maximum while the brakes cool. FWIW: descents at 70+ are not uncommon:
http://www.youtube.com/watch?v=pzL2ww-0QVg
http://www.youtube.com/watch?v=ncyt6Ofevv8