Wheels and Tires Overall width The linear distance between the exteriors of the sidewalls of an inflated tire, including elevations due to labeling, decorations, or protective bands or ribs. Ply A layer of rubber-coated parallel cords. Ply separation A parting of rubber compound between adjacent plies. Pneumatic tire A mechanical device made of rubber, chemicals, fabric and steel or other materials, that, when mounted on an automotive wheel, provides the traction and contains the gas or fluid that sustains the load. Radial ply tire A pneumatic tire in which the ply cords that extend to the beads are laid at substantially 90 degrees to the center line of the tread. Reinforced tire A tire designed to operate at higher loads and at higher inflation pressures than the corresponding standard tire. Section width The linear distance between the exteriors of the sidewalls of an inflated tire, excluding elevations due to labeling, decoration, or protective bands. Sidewall The portion of a tire between the tread and bead. Sidewall separation The parting of the rubber compound from the cord material in the sidewall. Snow tire A tire that attains a traction index equal to or greater than 110, compared to the ASTM E1136-93 (re-approved 2003, incorporated by reference, see §571.5) Standard Reference Test Tire when using the snow traction test as described in ASTM F1805-00 (incorporated by reference, see §571.5), and that is marked with an Alpine Symbol specified in S5.5(i) on at least one sidewall. Test rim The rim on which a tire is fitted for testing, and may be any rim listed as appropriate for use with that tire. Tread The portion of a tire that comes into contact with the road. Tread rib A tread section running around the circumference of a tire. Tread separation The pulling away of the tread from the tire carcass. Tread wear indicators (TWI) The projections within the principal grooves designed to give a visual indication of the degrees of wear of the tread. Wheel-holding fixture The fixture used to hold the wheel and tire assembly securely during testing. 144 Model 3 Owner's Manual