Originally Posted by
coldfeet
No, learn to feel for the point of maximum traction in the front wheel. On a good day, I can stop with the rear wheel off the ground. How can the rear wheel do anything in that situation? You can delay that point, ( rear wheel lift off ) by moving back, but the physics of the thing, means for most bikes, the front wheel makes the most deceleration.
Until the rear wheel lifts, the rear wheel is still contributing to the deceleration of the bike. True maximum braking with
only the front wheel isn't really reached until just before pitch over. Since it's rather dangerous to be dancing on that limit, most of us are going to keep the rear wheel in contact with the ground. If your rear wheel is in contact with the ground (or you aren't about to pitch over), you haven't reached maximum deceleration and, thus, your rear wheel is contributing to the overall deceleration of the bicycle. Moving the center of gravity of the bicycle rider system rearward doesn't just delay rear wheel lift, it actually contributes to the deceleration of the bicycle by a significant amount.
davidad agrees with most mountain bikers in that we practice letting off the front brake when the rear skids to maintain control of the bike for several reasons. A skidding wheel isn't that easy to control, a skidding rear wheel damages the trails, and a skidding wheel is an indication that you are close to pitch over. Hit a rock or object while the rear wheel is skidding and you might just stop the front wheel which results in ground making a painful imprint on your face.
Originally Posted by
DannoXYZ
Just try it, practice stopping in the shortest distances possible in a straight line. You'll find that the fastest deceleration is when you can get as much grip on the front as possible just before it slides or before it flips you over the bars. Doesn't matter what you try to do with the back since it's only 1% or less of the total braking-force at maximum deceleration-G.
Now, braking while cornering is a completely different matter.
The less contact the rear wheel has with the ground, the less contribution the rear wheel has to the overall deceleration of the bicycle. However, if the rear wheel is firmly planted on the ground as it would be in the early stages of braking or if the center of gravity is shifted rearward, the amount that it contributes is far more than 1%. For a cyclist that is seated on a bike in a 'normal' fashion (i.e. not shifted rearward), the amount the rear wheel contributes is around 0.1g. But for a cyclists in this position, the overall deceleration is only 0.5g so the rear wheel is contributing 20%, not 1%. This, of course, decreases as the weight is transferred more towards the front wheel during braking. But you can also keep the weight transfer from occurring too rapidly by shifting your weight rearward, which also happens to increase the deceleration ability of the bicycle.