08/09/2014
Tyre Glossary
Accelerator: A chemical that is used in rubber compounds.
Adjustment: An allowance given to a customer to be used toward the replacement of a tyre because of warranty issues.
Alignment: Inspection and the possibility of adjusting the caster camber and toe angles of the automobile’s suspension system in accordance with the manufacturer’s original specifications.
Antioxidant: A chemical used in rubber compounds that prevents surface oxidation, chunking, and cracking.
Aspect Ratio: The measurement of a tyre’s sidewall height. The calculation is derived from dividing the section height by the section width of the tyre.
Balance: To ensure weight is distributed evenly around the tyre and rim, resulting in a smoother ride.
Banbury Mixer: A large machine used in the production of rubber compounds for mixing all of the filler and ingredients together.
Bead: The part of the tyre that secures the tyre to the rim, normally constructed from a high grade steel wire and hard rubber compound.
Bead Seat: The section of a rim where the bead of the tyre rests.
Belts: These are layers of fabric or steel cords coated in a rubber compound providing the tyre with its strength.
Bias-Ply: A type of construction method used to build tyres where the cords in the body plies are placed diagonally from one side of the tyre to the other, normally from one bead to the opposite bead.
Bladder: A large, rubber, inflatable container used in the tyre molding and curing process of tyre production.
Blem of Blemished Tyre: A tyre which has cosmetic or minor imperfection but is still considered safe to use.
Bolt Pattern: The pattern of holes on a rim/wheel which the bolts that mount the wheel to the vehicle are put through.
Camber: The angle of the vertical center of the tyre to a vertical line viewed from the front of the tyre.
Camber Thrust: The force created by a tyre’s camber.
Carbon Black: Filler used in the rubber compounds. Its primary function is to be used as reinforcement filler.
Carcass: This is the body that gives the tyre its shape.
Carrying Capacity: The amount of load/weight a tyre can carry at its proper inflationary pressure established by the Tyre & Rim Association.
Chafer: A rubber-coated, abrasion-resistant material that is used to aid in preventing a tyre’s bead from rim damage and chafing.
Compound: The mixture of ingredients such as natural rubber, synthetic rubber, carbon black, and chemicals, put together in different ratios to form the building block from which tyres are manufactured.
Contact Patch: The area of the tyre that makes direct contact with the surface of the road.
Cord: The steel or fabric strands that form plies and belts in tyres.
Cord Angle: The degree of angle that the cords cross the center line of a tyre.
Crown: The center section (between the tyre shoulders) of the tyre’s tread.
Deflection: The change in the tyre’s vertical and lateral dimensions when it is placed under load.
Directional Stability: The tendency for a tyre to move in the direction it is steered to rather than following the contours of the road.
Diameter: The measurement of an unloaded tyre from one outer edge to the opposite edge.
Dynamic Balance: This is the balance of a tyre while in motion.
Eccentric Mounting: A condition where a tyre is mounted unevenly on a rim/wheel.
ETRTO: European Tyre and Rim Technical Organization.
Flotation Tyre: A tyre designed to do minimal damage to the lawn or soil surface.
Green Tyre: A tyre that has not yet gone through the process of vulcanization or curing in the tyre molding process.
Grooves: Channels in the tread pattern that allow water to flow out from underneath the tyre for wet weather driving.
Hoop Strength: The strength in the construction of the belt of a tyre is resistant to centrifugal strength, giving the tyre stability.
Hydroplaning: A loss of traction of a tyre on a road surface caused by wet weather conditions.
Inflation Pressure: The pressure of air inside the tyre.
Innerliner: A layer of rubber inside the tyre carcass that retains the air in a tyre.
Load Index: A numbering system that specifies the maximum amount of weight a tyre can carry at the speed indicated by the speed rating.
Load Range: This term replaces the former ply rating system and provides the load and inflation limits of a tyre.
LT-Metric: A sizing system used for light truck.
Match Mounting: A system of mounting a tyre where the high point of the tyre is matched with the low point of a wheel. These spots are normally designated by a dot or a sticker on the tyre and wheel.
Mounting Tyres: The action of putting the tyre on a rim. This should only be done by a professional for safety reasons.
M+S, M/S, M&S: A designation of a tyre that meets the requirements given by the RMA to be used in mud and snow conditions.
NHTSA: National Highway Traffic Safety Administration.
O.E.: This refers to the original equipment of the vehicle.
Over Inflation: A tyre that exceeds the maximum amount of air pressure recommended by the manufacturer.
Out of Round: A term used to indicate that the tyre is not completely round.
P-Metric: A tyre sizing system where the section width is shown in millimeters and the aspect ratio, type of construction, and rim diameter are shown in inches (P215/70R15)
Plies: The layers of rubber-coated fabric or steel cord.
Polyester: This is a synthetic material that is used in the body ply or belt of a tyre.
Polymer: A high molecular weight organic compound made up of many identical components which link to form a chain through a process called polymerization.
PSI: A measure of air pressure – pounds per square inch.
Radial: A construction method used to build tyres where cords of steel are coated in rubber and are laid across the crown of the tyre at an angle of 90 degrees.
Rayon: A synthetic cord material used in the construction of casings and belts of a tyre.
Retread: A process in which a new tread cap is applied to a casing of a tyre that has been worn down.
Rim: The piece of hardware a tyre is mounted on and then placed on the automobile or truck.
Rim Diameter: The diameter of the rim measured according to the tyre bead heel.
Rim Fl**ge: The outermost edge of a wheel’s rim where additional weights for balancing the tyre are positioned.
Rim Width: The distance between the flanges of a wheel.
RMA: Rubber Manufacturers Association.
Runout: The measurement of the "out of roundness" of a tyre that causes vibration and cannot be balanced.
Section Height: The vertical distance measured from the edge of the bead to the center of the crown in a tyre that is not under load.
Section Width: The measurement of a mounted tyre from the outside of one sidewall to the outside of the opposite sidewall.
Series: The designation of a tyre’s aspect ratio.
Shoulder: The section of a tyre where the tyre tread is adjoined to the sidewall.
Sidewall: The section of a tyre between the bead and the shoulder.
Sipes: Small, thin slots that are molded into the ribs or blocks of a tread pattern that aid in the traction of the vehicle in wet weather conditions.
Speed Rating: A letter coding system designated by the Tyre & Rim Association indicating the tyre’s durability at a particular speed.
Static Balance: A condition in which a mounted tyre has even weight around the wheel's axis when the tyre is not in motion.
Steel Belt: A layer of material constructed from steel cords and normally coated in rubber, placed on top of the casing used in the production of tyres.
Toe: This is the difference between the front and the rear edges of a tyre mounted on an automobile. If the front edges are closer together than the rear edges, the phrase toe-in is used. If the front edges are farther apart than the rear edges, it is referred to as toe-out.
Tread: The section of the tyre that is in contact with the road surface.
Tread Life: The length of service, measured in miles, of a tyre.
Tread Pattern: This is the configuration of voids, blocks, grooves, sipes, etc. of the tread constructed to provide some of the characteristics of a tyre.
Tread Void: Areas in a tread such as grooves and channels permitting water to be moved away.
Tubeless Tyre: A tyre that does not require an inner tube. This type of tyre construction utilizes an innerliner inside the casing, preventing air leakage.
Tread Wear Indicators(T.W.I.): Small tread blocks in a tyre’s tread pattern (the void area) measuring 2/32" in height that show when a tyre should be changed.
Tread Width: The measured distance from the outer edge of a tyre’s tread pattern to the opposite edge of the tread pattern.
Under Inflation: A tyre that has a lower amount of air pressure than recommended by the manufacturer.
UTQG: Uniform Tyre Quality Grading – A measuring system to compare a tyre’s performance based on test results for treadwear, temperature resistance, and traction.
Zero Toe: A condition where tyres on the same axle are positioned exactly parallel to each other.
