Posted: Wed Feb 18, 2009 2:12 pm
Ace Rimmer wrote:It's been a while since I've ridden a bike, but I have been on both kinds and unless those pads have spikes or something, they don't have near the power two feet connected to two legs.
Wrong and irrelevant.
On a surface with good grip, front wheel braking beats back wheel braking. As deceleration is increased, the weight of the bike and rider acts further forwards. Maximum deceleration is achieved when all of the weight is acting through the front wheel and the bike is on the point of flipping over. This can be achieved with a good front hand brake. At this point there is no weight acting on the back wheel, the only thing keeping it turning is inertia, and if it is braked too it will lock up without helping to slow the bike. Maximum rear wheel braking is achieved when the brake force equals the frictional force that the wheel can sustain without slipping, that force is itself proportional to the weight acting on the back wheel, so decreases with increasing brake force as weight transfers forwards.
The braking 'power' (force) applied to the wheels by any system depends on the mechanical advantage and coefficient of friction as well as the input force, so it is quite possible for a hand-actuated rim brake with good compound pads to achieve more force than a leg-powered grease-packed coaster brake without resorting to spikes. The mechanical advantage and pad compounds of rim brakes have improved a lot over the last decade or so.
The only way 'two feet and two legs' could decelerate a bike quickest is if the feet were placed on the ground forwards of the front wheel, and sufficient friction achieved to transfer all of the weight onto the feet.