Glossary


Alignment	"Wheel Alignment" is a general description relating to the adjustment of mechanical components that form part of the vehicle Steering and Suspension system.
Aquaplaning(CD)	A condition in which the tyres in a motor vehicle ride on a film of waiter instead of on the road surface, leading to complete loss of vehicle control.
Bead	The part of a fitted tyre which sits on the wheel.
Bead wires	A coil of high tensile steel wire treated to improve bonding when encased in a "matrix" of hard rubber. The casing plies are turned around the bead and are securely bonded to the structure when the tyre is cured.
Carbon black	Very fine, specially structured particles of carbon used in rubber compounds as a reinforcing filler.
Carcass	The structure of the tyre cords locked around wire beads..
Footprint	The portion of the tread in contact with the road.
Hysteresis	Actions and reactions: not all energy applied to a tyre is dispersed. When dealing with an elastic material like rubber energy is always absorbed and this creates heat build-up.
Load index	The LOAD INDEX is a numerical code associated with the maximum load a tyre 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 tyre manufacturer.
Rolling resistance	The capacity of a tyre to resist its natural "spinning" movement. The lower the rolling resistance, the greater the economy as less energy will be required to move the tyre with resultant fuel saving.
Service description	In addition to the Tyre Size Designation a tyre 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.
Shoulder	The area of a tyre where the tread and sidewall meet.
Sidewall	That part of a tyre between the tread and the bead
Silica	A reinforcing filler used in a rubber compound to provide higher tyre mileage and low rolling resistance
Speed category	Indicates a tyre's speed capability above 240 km/h and is included within the tyre size designation e.g. 215/50 ZR 15. In those cases where a Service Description is not shown consult the tyre manufacturer for actual speed capability and load capacity
Speed symbol	Indicates the max speed at which the tyre can carry a load corresponding to its load index (except for speeds above 210 km/h) under service conditions specified by the tyre manufacturer.
Tyre Compound	A "mix" or combination of raw materials used in the manufacture of the rubber compound of the tyre itself. By varying the percentage or the composition of the materials applied, manufacturers can produce different tyres for various purposes and with different performances.
Tyre Structure	The structural configuration of the carcass. The two main types of structure are "Radial" (where the plies are arranged in a way that the cords run at a 90 degree angle to the centre line of the tread) and "Cross-Ply".
Tread	That part of a tyre which comes into contact with the road surface.
Tread Pattern	The tyre design or pattern. This varies according to the application (i.e. tyres geared towards wet performance have more grooves and channels for optimum water dispersion, whilst dry/tarmac tyres have fewer grooves as their function is to maximise the contact area).
Tubeless	A tyre specifically designed for fitment without an inner tube on appropriate rims. Where "TUBELESS" does not appear on the sidewalls, tyres are intended for fitment with an appropriate inner tube..
Valve	The device used to adjust the inflation pressure.
Wear indicator	A raised section at the base of the grooves that indicates the tyre's legal minimum tread depth

Last Revised: 03-07-2007