Advanced Tire Terms

Speak Tire Like an Enginnering Boffin

ALL-SEASON HIGH-PERFORMANCE TIRES
Tires that deliver a measure of traction on snow and ice without sacrificing dry performance driving capabilities.

ALL-SEASON TIRES
Tires that provide a good balance of traction in rain or snow with good tread life and a comfortable, quiet ride.

ALL-SEASON TRACTION
Indicates the tire's ability to provide a balance of traction in wet, dry, and winter conditions.

APS
An advanced silica-based winter rubber compound that helps provide flexibility where the tread surface makes contact with the road.

ARAMID
A synthetic fabric used in some tires that is (pound-for-pound) stronger than steel.

BEAD CHAFER
A key component of the tire that is the contact point between the tire and the wheel, designed to withstand forces the wheel puts on the tire during mounting as well as the dynamic forces of driving and braking.

BEAD FILLER
Responsible for transferring propulsion and braking torque from the wheel rim to the road surface contact area.

BEAD TENSION STRUCTURE
Two sidewall plies wrapped around each bead wire in opposite directions providing lateral stability but flex to absorb road irregularities.

BELT
A rubber-coated layer of cords that is located between the body plies and the tread. Cords are most commonly made from steel but may also be made from fiberglass, rayon, nylon, polyester or other fabrics.

BIAS-PLY
A type of tire with crossed layers of ply cord running diagonally to the center line of the tread.

BOLT CIRCLE
The diameter of an imaginary circle drawn through the center of each lug nut hole and then measured from two holes that are directly across from each other. The measurement is used in selecting the proper wheel for replacement.

BRAKING TORQUE
A technique practiced by drag racers and road testers to improve their off-the-line acceleration; applying the brake and throttle at the same time, increasing the engine rpm until release of the brake.

BREAKAWAY
A term used to describe a loss of traction when negotiating a curve or when accelerating from a standing start. The tires slide against, instead of grip, the road surface.

BUTYL RUBBER
Synthetic rubber used to create today's tires. It is virtually impenetrable to water and air.

CAMBER
A wheel's inward or outward tilt from vertical, measured in degrees. The camber angle is adjusted to keep the outside tires flat on the ground during a turn.

CAMBER THRUST
Side or lateral force generated when a tire rolls with camber, which can add to or subtract from the side force a tire generates.

CARBON BLACK
This is a reinforcing filler which, when incorporated into the tire rubber compound, gives it a high resistance to wear.

CARCASS
The supporting structure of the tire consisting of plies anchored to the bead on one side and running in a radius to the other side and anchoring to the bead. Also called casing.

CARCASS PLY
Made up of thin textile fiber cables bonded into the rubber. These cables are largely responsible for determining the strength of the tire.

CARRYING CAPACITY
At a given air pressure, how much weight each tire is designed to carry. For each tire size, there is a load inflation table to ensure the inflation pressure used is sufficient for the vehicle axle load.

CASTER
The angle between a line drawn vertically through a wheel's centerline and the axis around which the wheel is steered; improves a car's directional stability and on-center feel.

CENTERLINE
An imaginary line down the center of the vehicle. Alignment tracking is measured from this line.

CENTRIFUGAL FORCE
The sideways acceleration, measured in g's, of an object in curvilinear motion. As a car traverses a curve, centrifugal force acts on it and tries to pull it outward. To counteract this, the tires develop an equal and opposite force acting against the road. Also called lateral force.

CORD
The strands of fabric forming the plies or layers of the tire. Cords may be made from polyester, rayon, nylon, fiberglass or steel.

CORNERING FORCE
The force on a turning vehicle's tires - the tire's ability to grip and resist side force - that keeps the vehicle on the desired arc.

CROWN PLIES
Provide the rigid base for the tread which allows for good fuel economy. The plies also provide centrifugal and lateral rigidity to the tire, and are designed to flex sufficiently for a comfortable ride.

CURB WEIGHT
Weight of a production vehicle with fluid reservoirs (including fuel tank) full and all normal equipment in place, but without driver or passengers.

DIRECTIONAL STABILITY
The ability of a vehicle to be driven safely and with confidence in a straight line and at high speed without being affected by pavement irregularities, crosswinds, aerodynamic lifting forces, or other external influences.

DOG TRACKING
Track is the width between the outside tread edges of tires on the same axle. Tracking, or more specifically "Dog Tracking", refers to a condition in which the vehicle is out of alignment, and the rear wheels do not follow in the path of the front wheels when the vehicle is traveling in a straight line. Also called tracking.

DRIFT
Drift refers to a vehicle deviating from a straight-line path when no steering input is given. Also called pull.

ECCENTRIC MOUNTING
Mounting of a tire wheel assembly in such a way that the center of rotation for the assembly is not aligned with the center of rotation for the vehicle's hub.

FILAMENT AT ZERO
Individual, spiral-wrapped nylon or aramid/nylon reinforcing filaments can be precisely placed in specific portions or across the entyre tread area atop the steel belts banded at zero degrees. Not only does this help retain tire shape, but it also enhances ride quality and steering precision.

FORE-AND-AFT WEIGHT TRANSFER
Transfer of weight from the front axle to the rear axle (or vice versa) caused by acceleration or braking. Acceleration causes weight transfer from the front axle to the rear axle. Braking causes weight transfer from the rear axle to the front axle.

FOUR-WHEEL-DRIFT
A handling term describing a car with its front and rear tires sliding in a controlled manner. The driver uses both throttle and steering to keep the vehicle on a prescribed path.

FREE RADIUS
The radius of the tire/wheel assembly that is not deflected under load.

GROSS AXLE WEIGHT RATING (GAWR)
The maximum weight that can be distributed among the tires on a given axle.

GROSS VEHICLE WEIGHT (GVW)
The weight of the vehicle and its contents (fluids, passengers, and cargo).

GROSS VEHICLE WEIGHT RATING (GVWR)
The maximum weight allowed for the vehicle and its contents. This value is established by the vehicle manufacturer and can be identified on the vehicle door placard.

INDENTATION
A normal, safe occurrence in a tire's sidewall where overlapping splices of fabric cords form indentations. This cannot occur on tread due to steel cable implantation.

INNER LINER
The innermost layer of a tubeless tire, compounded with virtually impermeable butyl rubber. Some air loss over time will occur. Check your pressures monthly to ensure safe reliable operation of your tires.

LATERAL WEIGHT TRANSFER
When a vehicle travels through a curve, weight is transferred from the wheels on the inside of the curve to the wheels on the outside of the curve. This is a result of the centrifugal force, or lateral force acting on the vehicle.

LOADED RADIUS
The measurement in inches from the wheel axle centerline to the ground when the tire is properly inflated for the load.

LOADED SECTION HEIGHT
The height of the section of the tire that is making contact with the road.

LOAD RANGE
Defines a range of maximum loads that tires can carry at a defined pressure.

LUG-CENTRIC
Wheels are manufactured to fit either the hub or the lugs. Lug-centric is matching the lug holes of a custom wheel perfectly to the lug pattern of the vehicle.

LUXURY PERFORMANCE TOURING TIRES
Generally designed for luxury sedans, this breed of tires blends performance handling with a comfortable, smooth ride.

OXIDATION
Rust process that takes place in the steel belts when moisture, via damage, is allowed to get inside the tire. This can result in the tire becoming unserviceable before normal replacement time.

ROLLING CIRCUMFERENCE
The linear distance traveled by a tire in one revolution (its circumference). This can vary with load and inflation. Rolling circumference can be calculated as follows: 63,360 divided by revolutions per mile = rolling circumference in inches.

RUBBER COMPOUND
A combination of raw materials blended according to carefully developed procedures. The rubber compound is specially adapted to the performance required of each type of tire.

STEEL BELT
The combination of steel cords covered with rubber that forms a strip or belt placed under the tread rubber and on top of the casing (carcass); ensures uniformity when the tire is rotating and helps prevent flats.

STEERING RESPONSE
A vehicle's reaction to a driver's steering inputs. Also the feedback that drivers get through the steering wheel as they make steering inputs.

SYNTHETIC RUBBER
Man-made, as opposed to natural, rubber. Most of today's passenger car and light truck tires have a relatively small amount of natural rubber in their content.

TOE
The difference in distance between the front and rear of a pair of tires mounted on the same axle.

TOE-IN
The fronts of two tires on the same axle are closer than the rears of the tires.

TOE-OUT
The fronts of two tires on the same axle are further apart than the rears of the tires.

TOE-OUT TURNS
Also known as Ackerman Angle. A vehicle's wheels on the inside of a turn follow a smaller radius than the tires on the outside of the turn, because the two front wheels steer at different angles when turning.

TORQUE
Turning or twisting effort, usually measured in lb-ft or Newton meters.

TORSION BAR
A long, straight bar fastened to the frame at one end and to a suspension part at the other; acts like an uncoiled spring that absorbs energy by twisting.

UNDERTREAD
Material between the bottom of the tread rubber and the top layer of steel belts; acts as a cushion that enhances comfort.

VARIABLE CONTACT PATCH
A system that maximizes the contact patch area during cornering through a combination of asymmetrical tread patterns and underlying belts.

WHEELBASE
The longitudinal distance from the center of the front wheel to the center of the rear wheel on the same side of the vehicle.

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