What are the functional differences of the 'long tail' brake pads (more pad on one rear facing side of the post than the front side) versus the symmetrical (same amount of pad on either side of the post) brake pads for cantilever and v-brakes. Why would I prefer one type over the other?
If you take a symmetrical pad with a given size, it is subject to two forces while braking:
The second force being much greater than the first, it is advantageous to mount an ASYMMETRICAL pad with the tail always rearwards, so that the asymmetrical reactive force (due to the shape of the pad) tends to neutralize the "toe-in" (or out?) effect created by the tangential force of the rim motion.
One caveat! In narrow forks, the tail can interfere with the fork itself, thus making it difficult to open the brake for wheel removal.
Hope this helps!