There are several reason the steel belt inside a tire might break. The most common reason is a manufacturer's defect. These belts are made to withstand quite a bit of abuse. If you notice your car is just not riding well, check out the tires. Common signs of a broken or bad belt are uneven tread wear. This is not just the usual type where it wears down on the inside and not the outside. This is where it might wear down on the outside on only a portion of the tire. You can also look for a bulge where the belt has become less round. A broken belt in the tire means its time for a new tire. There is no fixing it.