Originally Posted by cyccommute

"Everything you read" about using only the front brake is based upon a flawed interpretation of the physics of braking by road riders...who know very little about braking as a rule. While the maximum amount of deceleration you can realize is limited by the front brake, it's actually a trick of the math. If you are up on the front wheel without contact from the rear wheel on the ground and actually about to pivot around the front hub, that is the 'maximum' deceleration you can possibly realize from any brake. Most people don't want to brake that way.

When the rear wheel is still in contact with the ground, you haven't reached the maximum deceleration but you aren't about to experience asphalt dentistry either. But you are damned close to the maximum deceleration that you can achieve. The difference is minimal. The rear wheel, as long as it is in contact with the ground, is contributing something to the deceleration of the bike. If you are seated in a 'normal' riding position, the amount that the rear wheel contributes is around 0.1g. But the overall deceleration of the bike in that position is 0.5g. If you don't use your rear brake, you are giving up 20% of your braking power.

The deceleration ability of any bike can be improved pretty simply, however. Move the center of gravity, i.e. you, back and down even a little and the deceleration that you can squeeze out of the brakes doubles. A shift of your body by around 4" back and 2" down, increases the deceleration you can develop from 0.5g to around 1g. Watch a mountain biker brake. They throw themselves off the back of the saddle to increase their braking power and to keep the rear of the bike in contact with the ground longer. The last thing you want on a mountain bike is a nose wheelie.

Counteract that tendency of being pushed towards the front of the saddle by pushing off the back, you'll see dramatic improvements to braking.