If you get on pavement w/ the locker on and take a turn, you'll be instantly reminded that your locker is on by the noises your tires start making. In a turn an open rear end allows the outside tire in the turn to spin faster than the inside tire whereas when they are locked they can only go the same speed, so when you turn on pavement the tires start squallin where the inside tire wants to be going slower than the outside tire. Problem gets worse the sharper the turn, so on a windy road you'd really know...