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Section height
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The height of a tire, measured from its rim to its outer tread. Back to top
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Section width
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The distance between the outside of a tire?s sidewalls, not including any lettering or designs. Back to top
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Self-aligning torque
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When the tire is cornering, torque created at the road contact patch acts at a point somewhat to the rear of the actual wheel center due to pneumatic trail. This has the same effect as positive caster and tends to force the wheel back to the straight-ahead position. Back to top
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Series
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Tires with the same aspect ratio, or relationship of section height to section width. Back to top
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Service description
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Numbers and letters molded into the sidewall indicating the load-carrying capacity, load index, and the speed at which the tire can carry a load under specified conditions, or the speed rating. Also known as load index and speed symbol. Back to top
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Shimmy
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Wobbling of wheels from side-to-side on a vehicle. Shimmying can be caused by a variety of factors, including improperly balanced tires, poor alignment, and bent wheels. Back to top
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Shoulder
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The area of a tire where the tread and sidewall meet. Back to top
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Sidewall
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That portion of a tire between the tread and the bead. Protects the tire against impacts with curbs, etc. This is also where the sidewall markings can be found which tell you important information regarding the tire. Back to top
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Silica
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In 1992, Michelin discovered how to incorporate this new reinforcing filler into the rubber compound of tires. The discovery paved the way for compounds that provided resistance to wear, low rolling resistance, and good road-holding. Back to top
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Silica Tread Compound
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A compounding of silica with a specially formulated synthetic elastomer for exceptional grip on cold and wet surfaces, as well as reliable durability. Back to top
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Singles
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One tire mounted on each side of an axle (two tires per axle). Back to top
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Sipes
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Special slits within a tread block that open as the tire rolls into the contact patch then close, breaking the water tension on the road surface and putting rubber in contact with the road to maintain adhesion, increasing wet and snow traction. Back to top
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Size
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The combination of tire width, construction type, aspect ratio, and rim size used in differentiating tires. Back to top
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Slip
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The difference between the linear speed of the vehicle and the rotational speed of the tire. For example, if a tire is locked and sliding (e.g., not rotating) while the vehicle is still moving, then it is operating at -100% slip. Back to top
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Slip angle
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The difference between the direction the wheel is traveling and the direction the vehicle is traveling. Back to top
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Snow tire
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Also called winter tire; a special type of tire with a tread pattern and compound that gives better traction in snowy and icy conditions; identified by the M+S, M&S, or M/S on the sidewalls. Back to top
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Speed rating
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An alphabetical code (A-Z) assigned to a tire indicating the range of speeds at which the tire can carry a load under specified service conditions. Back to top
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Sprung weight
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The parts of a car that are supported by its springs, including the frame, engine and body. Back to top
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Squirm
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Flexing of the tread blocks between the belt package and the road surface. Less squirm means better steering response; more squirm means worse steering response. Back to top
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Stability
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Situation in which the driver maintains control of the vehicle. Back to top
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Standard load
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The amount of weight a given size tire can carry at a recommended air pressure. Back to top
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Star pattern
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A pattern for tightening the lug nuts when mounting the tire and wheel assembly to the vehicle. This pattern assures uniform pressure, prevents misalignment, and helps keep the wheel centered. Back to top
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Static balance
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Exists when the weight mass is evenly distributed around the axis of rotation. Static imbalance can be detected from vibrations through the seat, floor and steering column. Back to top
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Static loaded radius
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Distance from the wheel axis of rotation to supporting surface at a given load and stated inflation pressure. Back to top
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Steel belt
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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. Back to top
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Steering response
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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. Back to top
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Steering system
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The entire mechanism that allows the driver to guide and direct the vehicle; includes the steering wheel, steering column, steering gear, linkages, and wheel supports. Back to top
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Step groove
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A design feature at the base of the groove that generates an additional gripping mechanism in deeper snow. Back to top
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Stress Equilibrium Casing™
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A radial casing design that more evenly distributes the forces of acceleration, cornering, and braking throughout the contact patch, allowing for design enhancements in the shoulder and the use of softer, better gripping compounds. Back to top
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Structure
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The way in which a tire carcass is constructed. Radial structure tires can be identified by the word radial or by the letter R and today account for the majority of vehicle tires. Back to top
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Supporting Knobs Technology
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Small bumps in the shoulder grooves help to provide lateral block rigidity. Back to top
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Suspension
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The various springs, shock absorbers and linkages used to suspend a vehicle?s frame, body, engine, and drivetrain above its wheels. Back to top
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Symmetrical Tread Design
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Uniform tread pattern on both sides of the tread for better performance in specific conditions and on specific roads. Back to top
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Synthetic rubber
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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. Back to top
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Tensile Strength
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An object?s resistance to stretching or breaking when placed in tension. Steel belts in a tire are characterized and compared based on their tensile strength. Back to top
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Tire
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Also called pneumatic tire, a precisely engineered assembly of rubber, chemicals, fabric, and metal, designed to provide traction, cushion road shock and carry a load under varying conditions. Back to top
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Tire Designation
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An alphanumeric code molded into the sidewall of the tire that describes the tire?s size, including width, aspect ratio, rim diameter, load index, and speed rating. Most designations use the P-Metric system. Back to top
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Tire Mixing
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A situation in which tires of various brands, types, or sizes are mixed on a vehicle. This can lead to variations in the vehicle?s ride and handling characteristics. Back to top
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Tire Placard
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A metal or paper tag permanently affixed to a vehicle, which indicates the appropriate tire size and inflation pressures for the vehicle. The placard can ordinarily be found on either the driver?s doorpost, the glove box lid, or the fuel-filler door. Back to top
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Toe
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The difference in distance between the front and rear of a pair of tires mounted on the same axle. Back to top
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Toe-In
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The fronts of two tires on the same axle are closer than the rears of the tires. Back to top
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Toe-Out
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The fronts of two tires on the same axle are further apart than the rears of the tires. Back to top
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Toe-Out Turns
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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. Back to top
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Torque
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Turning or twisting effort, usually measured in lb-ft or Newton meters.
Torque-Locking Sipes. Back to top
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Torque-Locking Sipes
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Sipes with vertical undulation (into tread block) for added rigidity during cornering. Back to top
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Torsion Bar
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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. Back to top
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Touring Tires
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Generally offer increased tread life, comfort, and all-season traction. Back to top
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Track
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The distance between the outside tread edges of two tires on the same axle Back to top
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T & RA
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Tire and Rim Association. Back to top
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Traction
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The friction between the tires and the road surface; the amount of grip provided. Back to top
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Tramping
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A state in which a vehicle bounces up and down abnormally. Back to top
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Tread
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That portion of a tire that comes into contact with the road. It is distinguished by the design of its ribs and grooves. Provides traction in a variety of conditions, withstands high forces, and resists wear, abrasion, and heat. Back to top
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Tread Buffing
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Scraping rubber off the tread. Also known as shaving. Back to top
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Tread Depth
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The depth of usable tread rubber measured in 32nds of an inch. If a tire comes new with 10/32nds of rubber, you have 8/32nds of usable rubber. Tires must be replaced when the wear bars are visible at 2/32nds. Back to top
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Tread Life
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The life of a tire before it is pulled from service; mileage. Back to top
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Tread Rib
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The tread section that runs around the circumference of the tire separated by the tread grooves. Back to top
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Treadwear Indicator
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Narrow bands, sometimes called wear bars, that appear across the tread of the tire when only 2/32 inch of tread remains. Back to top
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Tread Width
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The width of a tire?s tread. Back to top
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Tri Side-by-Side Compounding
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A process that makes it possible to precisely place three different types of rubber compounds across the tread of a tire. Back to top
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Ultra-Low Profile Technology
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Specialized sidewall shape, bead area, and bead compound that enhance the durability and mountability of tires with very short sidewalls. Back to top
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Underinflation
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Operating a tire without sufficient air pressure to support the weight of the vehicle with occupants and additional load; could cause failure of the tire when heat is generated inside the tire to the point of degeneration of components. Back to top
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Understeer
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The handling characteristic in which the front tires break loose because they are running a larger slip angle than the rear tires. Also known as plowing. Back to top
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Undertread
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Material between the bottom of the tread rubber and the top layer of steel belts; acts as a cushion that enhances comfort. Back to top
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Unsprung Weight
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The weight of the parts of a vehicle not supported by its springs, including wheels and tires, outboard brake assemblies, the rear axle assembly, suspension members, springs, shock absorbers and anti-roll bars. Back to top
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UTQGS
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Also known as Uniform Tire Quality Grading Standards. A government-sponsored tire information system that provides consumers with ratings (from AA to C) for a tire?s traction and temperature. Treadwear is normally rated from 60 to 700. Back to top
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