doc_rot said:
Indeed. The idea is to remove the impact of suspension motion from the brake action. If you imagine the wheel locked by the brake, the bike not moving, and the suspension moving up and down, you will see that the contact patch of the tire actually moves back and forth very slightly. This is because the whole assembly is rotating around the swing arm pivot. This adds and subtracts very slightly from the action of the brake as the suspension moves, making the brake slightly more and less effective. How important this is no doubt depends on the aptitude of the driver. For most of us, evidently this is so minor that it need not be addressed, but for the ultra skilled, getting out that last little bit of performance likely is of some use. Although the value of the back brake certainly is quite small when you unload the back of the bike when braking hard, that same unloading makes controlling whether the wheel locks or not a very sensitive process, so adding that little refinement may be of use to some riders.
