A
Air Pressure: The amount of air within a tire, measured in pounds per square inch (PSI).
All-Season Tire: A tire designed for use in various weather conditions.
Aspect Ratio: The ratio of a tire’s sidewall height to its width. It is measured in percentage (%).
Alignment: Adjusting the angles of the wheels to ensure proper tire contact with the road.
Alignment Shim: A set of tools used to adjust wheel alignment.
All-Terrain Tire: A tire designed for off-road and on-road use.
All-Weather Tire: A type of all-season tire with better wet and snow traction than the standard all-season tire.
Aquaplaning: A loss of traction on wet roads due to a film of water between the tire and the road surface.
Anti-Lock Braking System (ABS): The Anti-Lock Braking System (ABS) is a safety feature in vehicles that prevents wheels from locking up during braking, thereby maintaining traction and steering control.
Average Tread Depth (ATD): The measurement of the average depth of a tire’s tread.
B
Balancing: The uniform distribution of weight in a wheel and tire assembly.
Bead: The part of the tire that sits on the rim of the wheel.
Bead Seating: The process of properly fitting the tire bead to the rim.
Bead Wire: A steel wire located within the tire’s bead to help secure it on the rim.
Bead filler: A rubber compound placed inside the bead of a tire to provide stiffness and shape. It enhances the tire’s fit and performance on the wheel.
Bias-Ply Tire: A tire with cord plies that crisscross at an angle to the centerline.
Belted Tire: A tire with steel belts beneath the tread for added strength.
Block Tread: A tire tread pattern consisting of large, square tread blocks.
C
Caster: The angle of the steering axis when viewed from the side.
Camber: Camber is the angle of the wheels relative to the vertical axis of the vehicle when viewed from the front.
Carcass: The tire carcass is the internal framework of a tire, consisting of layers of fabric and cords.
Center Bore: The hole in the center of the wheel for hub mounting.
Chamfer: A beveled edge on a tire tread block for improved performance.
Circumferential Grooves: Long, continuous grooves running around the tire to channel water away.
Cold Inflation Pressure: The tire’s air pressure when it’s cold.
Contact Patch: The portion of the tire that makes contact with the road.
Cord Plies: Layers of fabric or steel within the tire that provide strength.
Cornering: Cornering refers to a vehicle’s ability to navigate turns and curves with stability and control.
Curb Rash: Damage to the wheel or tire caused by contact with a curb.
D
DOT Number: The Department of Transportation code on a tire for identification.
Dry Rot: Cracking and deterioration of the tire’s rubber due to age and exposure.
Dry Traction: Dry traction refers to a tire’s ability to grip and maintain stability on dry roads.
F
Flat Spot: A portion of the tire tread that has become flat due to extended parking.
H
Handling: Handling refers to how well a vehicle responds to the driver’s steering, braking, and acceleration inputs.
I
Inflation Pressure: The amount of air pressure in the tire, measured in pounds per square inch (PSI).
Inner Liner: The innermost layer in tubeless tires that holds air and seals against leaks.
L
Load Index: A numerical code indicating a tire’s maximum weight-carrying capacity.
Load Range: The tire load range indicates the tire’s strength and its ability to contain air pressure, often represented by letters like B, C, D, etc.
Lug Nuts: Fasteners used to secure the wheel to the hub.
Lug Centric Wheel: Wheels that rely on the lug nuts to center them on the hub.
Lug Studs: The threaded studs on which the lug nuts are fastened.
M
Mud Terrain Tire: A tire with deep, aggressive tread, and robust sidewall designed to use for challenging off-road conditions.
N
Negative Camber: When the top of the tire leans inward toward the vehicle.
Nitrogen Inflation: Filling tires with nitrogen instead of air for improved pressure retention.
O
Overinflation: Overinflation refers to the condition where a tire is inflated beyond its recommended pressure limit. This can lead to decreased traction, uneven tire wear, and an increased risk of tire blowouts.
P
P-Metric Tires: A system of tire sizing based on millimeters, aspect ratio, and diameter.
Performance Tire: A tire designed for high-speed and handling capabilities.
Plus Sizing: Installing larger diameter wheels with lower profile tires.
Ply Rating: A rating that indicates the tire’s load-carrying capacity.
R
Radial Tire: A tire in which the cord plies are arranged radially from the center.
Radial Runout: The measurement of the wheel’s deviation from a true circle.
Rim Diameter: The measurement of the wheel’s diameter, usually in inches.
Rolling Resistance: The force required to roll a tire on a surface.
Run-Flat Tire: A tire designed to be driven on for a limited distance after a puncture.
S
Siping: Thin slits in the tread that improve traction on wet surfaces.
Spare Tire: A smaller, emergency tire carried in the vehicle for temporary use.
Speed Rating: A letter code indicating the maximum safe speed for the tire.
Staggered Fitment: Using larger rear tires than front tires for improved handling.
Steel Belt: Steel reinforcement within the tire’s construction for added strength.
Studded Tires: Studded tires are specialized winter tires that have metal studs embedded within the tread. These studs provide enhanced grip and control on icy and packed snow roads by piercing into the ice.
Summer Tire: A tire optimized for warm weather conditions.
T
Temperature Rating: The tire temperature rating, part of the Uniform Tire Quality Grading (UTQG) system, indicates a tire’s ability to withstand and dissipate heat under load. Ratings are classified as A, B, or C, with A being the highest.
Tread: The pattern on the tire’s outer surface that provides traction.
Tread Blocks: The individual sections of the tire’s tread pattern.
Tread Depth: The measurement of the thickness of the tire’s tread.
Tread Pattern: The specific design of the tire’s tread blocks and grooves such as symmetric, asymmetric, and directional tread patterns.
Treadwear Rating: A number that indicates a tire’s expected tread life.
Tubeless Tire: A tire designed to hold air without an inner tube.
Traction Rating: A measurement of a tire’s ability to grip the wet road surface.
U
Underinflation: When a tire has less air pressure than recommended.
Uniform Tire Quality Grading (UTQG): A rating system of treadwear, traction, and temperature resistance for tires.
V
Valve Stem: The component used to inflate and deflate the tire.
Vehicle Placard: A label on the vehicle specifying recommended tire pressure.
W
Wheel Offset: The distance between the wheel’s mounting surface and the wheel’s centerline.
Wheel Backspacing: Wheel backspacing is the distance from the innermost point of the wheel’s mounting surface to the wheel’s back edge. It determines how far the wheel sits inside the wheel well, affecting clearance and vehicle stance.
Wheel Spacers: Devices used to create more space between the wheel and the hub.
Wheel Studs: Wheel studs are threaded fasteners on a vehicle’s wheel hub that secure the wheels to the vehicle. They protrude outward, allowing the wheel to be mounted and secured with lug nuts.