Originally Posted by
Steely Dan
i 've read that too, but i don't necessarily believe it. on my road bike (ultegra calipers) i can definitely stop faster from the hoods when i engage both front and rear as opposed to just the front (from the drops, i can get better leverage on the brake levers and it makes less difference). simple physics tells you that the front brake does the lion's share of the braking work, but the rear brake is not useless in my experience of decades of cycling.
My guess is you aren't really likely to experience the situation where all the braking force has actually transferred to the front wheel when applying both brakes until you are just about to go over the handlebars. There is a reason you have both brakes.
So here's where I'm geeking out a bit. You both seem to agree with my experiential conclusion that using both rear brakes does, in practice, shorten stopping distances. This has perplexed me for a while because of the stature of the people saying it shouldn't be so. I studied the force equations involved and mathematically there is no question that the absolute minimum possible braking distance is indeed achieved when the amount of force applied is sufficient to raise the rear wheel off the ground, and it does look like with proper weight distribution that leaves room for a safe stop before you go over the bars. Hence my theory that it must be possible to reduce my braking distance by adding more braking force to the front wheel.
FWIW, I have gone over the handlebars twice in recent years. The first time was when I was a rookie commuter 5 years ago, using V-brakes and an ill-fitting flat bar bike. I believe weight distribution was to blame in that case. The other incident was a crash in a cyclocross race where I was braking hard while going down hill. I know for a fact that that one was rider error.