Dictionary of Tyre Terminology
Aquaplaning
Effect of water slipping of the tyre, i.e. loss of the contact between tire and roadway due to water wedge in the thick layer of water (>0.5mm), when vehicle moves on wet roadway.
Asymmetric Tread Pattern
It is a non-identical design of inner and outer parts of tire tread. Usually these are big tread blocks located on the outer part of the tread for the increase of stability of the vehicle when passing turns, maneuvering and experiencing action of other corner forces, and small tread blocks on the inner parts of the tyre for water dissipation. It is important to fit tyres with asymmetric tread patter to the rim correctly (its outer part should be on the outside of the rim). The outer side of the tyre is marked with word “OUTSIDE” on its side.
Asymmetric Tyre
A tyre that has asymmetric tread pattern (see Asymmetric Tread Pattern above). It is important to fit tyres with asymmetric tread patter to the rim correctly (its outer part should be on the outside of the rim). The outer side of the tyre is marked with word “OUTSIDE” on its side. Note: If you think that a tyre has an asymmetric tread pattern but there are no “INSIDE” or “OUTSIDE” markings, then this tyre is NOT asymmetric.
Balancing
Operation that is necessary when applying a tyre to the rim for elimination of unbalance and fluttering of wheel. Balanced wheel rotates with equal distribution of weight of the rim and tyre.
Bead
Rough part of the tyre designed for its fitting and sealing (in case of tubeless tyre) on the wheel rim. Inextensible ring made of steel rubberized wire makes the base of the bead. The bead consists of carcass cord layer, wrapped around wire ring, and circular or profile rubber filler. Steel wire ring provides bead with necessary strength and ruggedness while filler gives integrity and smooth transition from hard ring to the sidewall rubber. The outer side of the bead contains rim strip made of rubber-coated fabric or cord that protects the bead from scuffing against the rim and from damage during tyre fitting and stripping.
Breaker
Part of tyre consisting of cord layers and located between the carcass and tread of the tyre. It enhances the connection between the carcass and tread, and prevents its ply separation due to outer and centrifugal forces, dampers shock stress and increases carcass resistance to mechanic damages. Breaker in general determines strength properties of tyres.
Carcass
The most important load-bearing part of tyre providing its strength, accepting inner air pressure and transmitting loads from external forces, which apply from the road, to the wheel. Carcass consists of one or more overlapped plies of rubberized cord. Depending on the structure of carcass, dimensions, safe load and air pressure in the tyre the number of cord plies of carcass can vary from 1 (for motor car tyres) to 16 and more (in tyres for trucks, agricultural machinery, etc.).
Cord
It is a rubber-coated fabric layer consisting of dense sturdy threads of the base and sparse thin threads of filler, which give well rubberizing of cord threads, provide flexibility and strength. Cord is produced form cotton, viscose or capron fiber. Nowadays metal cord consisting of threads made of steel wire 0.15mm in thickness is used more commonly. There are some other more expensive materials (for example, Kevlar) that cannot be used as widely due to their expensiveness.
Finishing Wheel Balancing
This is the balancing without removing wheels from the vehicle. In case of finishing wheel balancing the wheel will be balanced with the account of inaccuracies of vehicle parts that transmit rotation to the wheel.
Lamel
Zigzagging cuts in tread blocks. It increases suction on wet, snowy and icy surfaces.
Motor Vehicle Tyre
Piece of hardware made of rubber, chemical elements, fabrics and metal components specially designed to provide movement of transportation means, ensure redemption of irregularities of roadways and take loads in different conditions.
Pneumatic Tyre
It’s a hard shell meant for mounting on wheel rim and filled with pressurized air.
Radial Tyre
A method of tyre construction, which incorporate reinforcing cords distributed radially relative to the hub (at 90 degrees to the direction of travel).
Reinforced tyres
Tyres designed to sustain heavier loads and higher air pressure in comparison with usual tyres. These tyres usually marked with “C” letter on the sidewall that follows size marking, for instance: 195/75 R16 C.
Rim
Part of the wheel the tyre mounts and seats upon.
Rolling Resistance
It is the force produced by tyres, which resists the movement of vehicle (or the force required for the vehicle to keep moving at a certain speed). Tyres with the least rolling resistance allow for more fuel economy.
Shoulder
Part of the tread located between the tyre tread and sidewall. It increases side sturdiness of tyre, accepts part of side loads transmitted from the tread and improves interconnection of the tread and carcass.
Sidewall
Tyre part located between tyre shoulder and bead, and which is a relatively thin layer of flexible rubber that continues the tread on the sidewalls of carcass serving for protection against mist and mechanic damages. Sidewalls have mark signs of tyre on them.
Single Wheel
A wheel installed on the wheel hub and bearing single tyre.
Tread
It is a massive layer of high-duty rubber contacting the road surface while wheeling. Its external surface has a raised pattern in the form of ridges and grooves between them (the so-called tyre “treadmill”). The tread protects carcass from mechanic damages, determines wear-resisting properties and road grip capacities of tyres as well as the levels of vibration and noise. The raised pattern determines tyre fitness for different road conditions. Tyres are divided into four major categories on the basis of tread pattern type: road (summer, all-season), universal, winter, and rough terrain.
Tubeless Tyre
A tyre that has an internal layer, which prevents air leakage from it. In this case inner tube is not required.
Twin Wheel
A wheel consisting of two single wheels installed on one hub.
Tyre Label
(On the vehicle). Paper or metal label attached to the vehicle (on standing pillar, on gas cap lid or glove-box door) that shows the recommended tyre size and air pressure in tyres for this vehicle.
Unbalance
State in which an abnormal vibration of the vehicle occurs. Usually such vibrations occur due to unbalanced wheels, as well as many other things.
- Inadequacy of the rim characteristics to the vehicle type,
- Disturbance of geometrical pattern of rim rotation,
- Partial breakdown of parts of the vehicle that transmit rotation to the wheel,
- Improper installation of the wheel,
- Improper mounting of the tyre on the rim,
- Breakage of tyre.
Wheel
It is a rotating component of a vehicle transmitting driving torque and accepting the load from vehicle weight. Wheel is located between the tyre and wheel hub. Usually wheel consists of two parts – rim and disk.
Wheel Disk
Part of the wheel that connects the rim and wheel hub.