Originally Posted by FBinNY

Both MC and bicycles can be brought to a point where 100% of the braking power is off the front brake. You see it when folks stunt and do front wheel wheelies balancing on the front wheel with the rear off the ground.

At that point the rear brake no longer matters, but before that it can be brought to where it ALMOST doesn't matter, (before it lifts) leaving some margin for error, especially since most people aren't stunt riders. So, I used 95% as a point of reference, but it can be anywhere shy of 100% depending on the rider's skill in balancing braking force.

As I mentioned, in an emergency maximum effort stop, the rear brake doesn't help, but using it helps by providing feedback and an early warning of impending tip. So we agree on the principles involved, and can skip debating the finer points.