Are Your Tires Worn Out?
Place two average adult feet side by side on a piece of paper and draw a box around their edges. The area of this box is about the same as the area of your tires in contact with the road on an average automobile. Tires are your only contact with the highway, and collisions result when that contact is lost.
All tires on your vehicle must have at least 1.5 mm (2/32") of tread depth on any two points of the tire more than 38 cm (15") apart. If the tread is worn down to show any two adjacent tread wear indicators, the tire is worn out. Winter tires must have a minimum of 3.5 mm (4/32") of tread.
Tires must be free of lumps or bulges. These result from internal breakdown of the tire.
The tire must not leak or have any cord breaks. Cracks, cuts or snags more than 2.5 cm (1") long and deep enough to expose the ply cords in the tread mean the tire is no longer serviceable.
Radial tires must be used on all 4 wheels when your vehicle has only 4 wheels. For vehicles with more than 4 wheels, radial and bias ply tires may be mixed, but the same type of tire must be used on each side of the same axle.