Originally Posted by
Polaris OBark
I think the reason it is more efficient is that about 80% of the rider weight is effectively loaded onto the front brake, so I would guess that it would proportionally heat up more. You have a fixed amount of kinetic energy to dissipate as heat, and that scales linearly with mass. So if the rear brake is doing half the work of slowing the rider, it should absorb half of the heat. If you only use the rear (or front) brake, it will be the only one that heats up.
It doesn't work that way. Try it sometime and you will see it requires much more lever pressure (equates to more friction) to get the rear to slow than the front. If you do this with disc brakes, you can easily feel that the rear brake will get much hotter - be careful with this test as you can easily burn yourself.