Apexes: Rubber fillers in the bead and lower sidewall area to provide progressive transition from the stiff bead area into the flexible sidewall.
Bead Bundle: The steel bead bundle properly seats and seals the tire on the rim and maintains it in position.
Belt: Multiple low angle steel cord layers providing strength to the tire, stabilizing the tread and preventing penetrations into the carcass.
Carcass or Casing: The body of the tire consisting of the beads, sidewalls and tread package.
Chafer: A layer of hard rubber that resists erosion of the bead zone by the rim flange.
Chipper: Layer of steel cables over the radial ply turn-up to reinforce and stabilize the bead-to-sidewall transition zone.
Compound: A mixture of rubber, oils and other materials that make up (most commonly) the tread.
Flap: A rubber band placed between tube and rim. It protects the tube from chafing and prevents damage to the tube by the rim.
Inflation pressure: The pressure to which a tire should be inflated when it is cold. It is normally expressed in kPa (kilo Pascal, 100 kPa = 1bar), psi (pounds per square inch) or bars (1 bar = atmospheric pressure which is approximately 14.5 psi depending on height related to sea level).
Innerliner: A layer of rubber in tubeless tires specially compounded to prevent air loss.
Load Index: The maximum load a tire is permitted to carry.
Radial: The body ply cords are placed straight across the tire from bead to bead. In addition, radial tires have belt plies which run essentially circumferentially around the tires, under the tread. They constrict the radial ply cords and stabilize the tread area.
Ply: The radial (900) ply transmits all load, braking and steering forces between the wheel and the road and withstands the burst loads of the tire under operating pressure.
Regrooving: Cutting worn grooves to a deeper design depth with a hot iron to increase the life of a tire.
Retreading: The replacement of a worn tread with a new one to extend the life of a truck carcass.
Rolling Resistance: Rolling resistance is exactly what it says. So the lower the rolling resistance the less effort is required to move the tire. This is a result of a multitude of influences including the tread compound and tire construction. It directly relates to fuel economy.
Rim: Alternative word for wheel which is commonly used in the tire trade. It is also the part of a wheel on which the tire is mounted.
Sidewall: The part of the tire providing protection for the ply and withstanding flexing and weathering.
Speed rating: The maximum speed a tire is permitted travel at.
Tread: Outer layer of the tire that contacts the road providing primarily traction and protects the carcass underneath.
Tread pattern: The design of the grooves to maximise grip whilst also maximising water clearance
Tube: A separate air chamber, compounded to prevent loss of air, inserted into tube-type tires.
Tubeless: A tire that does not require a tube.