True, most of the stopping power does come from the front wheel. However the V brake on the front wheel works well. Even though the wheel is only 20" the rim is made from aluminum alloy and there is plenty of surface area so brake heating is not much of an issue. The old V brake on the rear wheel provided 10% of the braking power so it was pretty much useless. Adding the disc to the rear basically made the rear braking power equal to the front. This takes a lot of stress off the front brake pads and adds a big safety margin in case the front brake fails.