The shortest stopping distance for straight line braking on dry, smooth roads is weight back, full on front brake, to the point that the rear wheel would just lift off the ground. This requires tremendous force on the front brake, flawlesss modulating, and excellent balance. However, this is not within the ability of most riders, and does not account for brake fade due to overheating, which is reduced when using two brakes. Also does not include wet or rough roads, where front wheel lock up is more likely, and turning when braking, which increases the likelihood of the front wheel locking and skidding out from under you.