Join Date: Dec 2005
Location: London, UK
Bikes: Trek T200 plus enough others to fill a large shed
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OK I didn't explain very well in my original post, so here goes.
Maximum braking friction between the tyre and the road occurs when there is a degree of slip between the road and they tyre, i.e. the wheel is rotates slightly less fast than the road is moving. Friction falls off sharply once a full locked-wheel skid starts. Mathematically speaking if you draw a curve of friction versus relative wheel-road speed, there is a sharp peak just before the wheel skids, so to stop as fast as possible you need to brake hard enough to get into this zone, but not beyond.
Thus you need brakes that are strong enough to lock the wheel, but need enough skill to:
a) modulate braking to nearly but not quite skid
b) if a skid develops quickly reduce braking to get back into maximum braking zone
c) not fall off while doing this.
Note that weight transfer means that a different level of braking is possible at the front and rear of a bike (and changes with decelleration level), so it's not easy to do well. Thus practice as referred to in the Santana page I mentioned is required.
ABS systems (Anti Blockier System in German = Anti Skid System) maximise braking by braking until the wheel locks, then relax the brake slightly until that the wheel rotates, then braking hard again. Thus the system keeps the braking effort close to the peak of the friction curve. A skilled racing driver on a dry surface can thus outbrake an ABS system by knowing exactly where the peak is and braking to that level. However on surfaces with unknown or variable friction an ABS system will be far superior as it modulates each wheel individually. This is effectively what you're trying to do on a bike or non ABS equipped car by adopting cadence braking where you brake hard, release slightly then brake hard again.Other advantage is that the car still steers under braking as the wheels aren't locked.