Glossary “tire free diameter” Definition:
The free diameter of a tire is the distance of a horizontal line through the center of the spindle and wheel to the outer edges of the thread.

Glossary “tire function” Definition:
1). To cushion the vehicle ride to provide a comfortable ride for the occupant; reduces jolts to the vehicle caused by road irregularities. 2). To support the vehicle weight. 3). To develop traction to drive and steer the vehicle under a wide variety of road conditions. 4). To contribute to the directional stability of the vehicle, and absorb all the stresses of accelerating, braking, and centrifugal force in turns.

Glossary “tire contact area” Definition:
The footprint, patch, or patch area of the tire that is in contact with the road surface when the tire is supporting the vehicle weight.

Glossary “tire coding” Definition:
Information required by federal legislation to be placed on all tires, such as: manufacturer and tire name, size designation, maximum load-carrying characteristics, limit, and range, a ten-digit DOT serial number indicating where and when it was made, and the letter A, B, or C, indicating conformity to a uniform tire quality grading system.

Glossary “tire concentricity” Definition:
Condition where the plies and/or belts are not level across the tire tread and are somewhat cone shaped. This causes a pull to one side as the car is driven straight ahead if the tires are on the front of the vehicle.

Glossary “tire construction” Definition:
Tire construction design has two wire beads, bead filler, liner, steel reinforcement in the sidewall, sidewall with hard side compound, rayon carcass plies, steel belts, jointless belt cover, hard under-tread compound, and hard high-grip tread compound.

Glossary “tire chain” Definition:
Specialty chains which may be placed over the tires to improve traction when driving on ice or snow; typically used in emergency situations such as driving on snow-covered or ice-covered mountain roads.

Glossary “tire changer” Definition:
Machine for quickly dismounting and mounting tires on and off of wheels.

Glossary “tire carcass” Definition:
The plies that make up the underbody of the tire.

Glossary “tire casing” Definition:
Layers of cord called plies on which the rubber tread is applied.

Glossary “tire balancing” Definition:
Procedure of using special equipment for identifying the lighter portions of a tire and adding weights until opposite tire sections weigh the same.

Glossary “tire bead” Definition:
Term used for bead.

Glossary “tire belt” Definition:
Term used for belt.

Glossary “tire black” Definition:
Black liquid dressing used to refresh the appearance of tires.

Glossary “tire aspect ratio” Definition:
Term used for aspect ratio. Also known as series number.