Glossary

AlignmentThe term 'Wheel Alignment' is a general description of the service required to check and correct any of the mechanical devices which from part of the vehicle Steering and Suspension system.
Aquaplaning(CD)A condition in which the tires in a motor vehicle ride on a film of waiter instead of on the road surface, leading to complete loss of vehicle control.
BeadThe area of the mounted tire which seats against the wheel.
Bead wiresHigh tensile steel wire in a coil shape, treated to give good adhesion with rubber, and encased in a 'matrix' of hard rubber. The casing plies are turned around the bead wires and are secure bonded to the structure when the built tire is vulcanized.
Carbon blackVery fine, specially structured particles of carbon; used in rubber compounds as a reinforcing filler.
CarcassThe structure of the tire cords locked around wire beads..
FootprintThe portion of the tread in contact with the road.
HysteresisActions and reactions: not all energy applied to a tire becomes totally absorbed by the latter; there is always an energy loss that transforms into "heat". When dealing with an elastic material like rubber.
Load indexThe LOAD INDEX is a numerical code associated with the maximum load a tire can carry (except for loads at speeds above 210 km/h) at e speed indicated by its Speed Symbol under the conditions specified by the tire manufacturer.
Rolling resistanceThe capacity of a tire to contrast its natural "spinning" movement. The lower the rolling resistance, the more economic it is to roll the tire as less energy will be required to "roll the tire" with a resulting fuel saving and higher mileage.
Service descriptionIn addition to the Tire Size Designation a tire may be identified by a Service Description consisting of a load index (or two Load Indices in the case of single/dual fitments) and a speed symbol.
ShoulderThe area of a tire where the tread and sidewall meet.
SidewallThat portion of a tire between the tread and the bead
SilicaA reinforcing filler used with the rubber compound to provide higher wearing resistance and low rolling resistance.
Speed categoryIndicates tire speed capabilities above 240 km/h and are included within the tire size designation e.g. 215/50 ZR 15. Generally, Service Description is not shown on such tires. For actual speed capabilities and load capacities, consult the tire manufacturer concerned.
Speed symbolIndicates the max speed at which the tire can carry a load corresponding to its load index (except for speeds above 210 km/h) under service conditions specified by the tire manufacturer.
Tire CompoundA "mix" or combination of raw materials used in the manufacture of the rubber compound of the tire itself. By varying the percentage or the composition of the materials applied, manufacturers can produce different tires for various purposes and with different performances.
Tire StructureImplies the method used to manufacture the tire carcass. The two main methods are "Radial" (a tire with plies arranged in a way that cords in the body run at 90 degree angles to the center line of the tread) and "X-Ply".
TreadA portion of a tire which contacts the road surface.
Tread PatternThe tire design or "sculpture". It varies according to the tire purpose (i.e. rain/wet are more grooves and channels for optimum water dispersion, whilst dry/tarmac tires are less grooved as they function is to maximize the contact area with the ground).
TubelessA tire specifically designed for fitment without an inner tube on appropriate rims. Where no TUBELESS appears on the tire sidewalls, tires are intended for fitment with an appropriate inner tube..
ValveThe device used to let air in or out of the tire and retention.
Wear indicatorA rubber nub placed inside a groove of the tire tread to indicate the legal minimum depth of the groove itself.

Last Revised: 14-07-2006