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{ Useful Info.
Tire Terminology:
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S-Rated
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A speed rating category for vehicles with a top speed up to 112 mph. |
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Safety Bead
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The raised area circling the rim of the wheel and located slightly inward from the bead sear; required on all specialty wheels driven in street use to keep the tire from slipping into the rim bell, if accidentally deflated. |
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Section Height
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The distance from the bottom of the bead to the top of the tread. |
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Section Width
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The distance from sidewall to sidewall, exclusive of any raised lettering. |
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Self-Aligning Torque
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The force which causes a tire/wheel assembly to return to its straight ahead position after a turn. |
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Semi-trailing Arm
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A rear suspension system that sues a large A-arm for each wheel; its pivot axis is set between the 0 angle of a swing axle and the 90 of a trailing arm to a line running straight across the car. |
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Series
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This is the part of the size designation in tires which gives the ratio of the height of a tire (from the rim to the top of the tread) to the width of the tire (from sidewall to sidewall). It is also referred to as the aspect ratio of a tire. |
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Service Description (Load
Index/Speed Symbol)
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A speed rating system which describes the load capacity and high speed of a tire; includes numerical load indexes and alphabetical speed symbols. |
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Shimmy
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A rapid oscillation or wobble of a wheel and tire assembly about the steering axis. |
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Shock Absorber
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A "damper" between the body or frame of the car and the suspension; used to cushion road bumps and bounces and keep the tire in contact with the road. |
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Shoulder
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Outer edges of tire tread. |
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Shoulder Gauge
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The total thickness of a tire in the shoulder area. This is invariably the thickest part of the tire and this gauge directly affects the running temperature of a tire. |
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Sidewall
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The side of a tire between the tread shoulder and the rim bead. |
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Singles
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A tire and wheel assembly, mounted, alone, on one side of an axle. |
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Sipes
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Small, narrow slots molded into the ribs of the tread design which increase the traction edges of the tire and increase the traction ability of the tire on wet pavement. |
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Skid Resistance
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Maintenance of grip on the road and resistance to slide or slip, either longitudinally or laterally. |
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Slip
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The change in distance traveled per tire revolution due to driving or braking conditions; expressed as a percentage of the distance traveled under a free rolling condition. |
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Slip Angle
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The difference between the direction a tire is traveling and the direction it is pointing. |
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Slots
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Grooves generally positioned in the ribs and shoulder areas of some tires which aid in wet pavement traction. |
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Speed Rating System (Speed
Category Markings)
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An alphabetical system describing a tire's capability to travel at established and predetermined speeds. |
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Spindle (or Knuckle)
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A device connected to a vehicle's control arm by a ball joint; it is moved by the steering arm to change the direction of the wheels and to transmit braking torque. |
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Sprung Weight
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The total weight of a vehicle that is supported by the suspension system. |
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Squirm
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The footprint distortion of a rolling tire; usually hourglass in shape on a straight road and crescent-shaped on curves. |
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Stability
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The ability of tires to maintain direction of a vehicle on curves without causing excessive body sway. |
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Stacked Belt
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A belt design in which both layers are of equal width. |
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Standard Load
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A P-Metric tire with a maximum inflation pressure of 35 psi. |
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Star Pattern
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The proper method for sequential torquing of lug nuts in a 5-lug bolt circle. |
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Static
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Having no motion. |
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Static Balance
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Balance at rest. A condition in which a tire and wheel assembly has equal weight around the wheel's axis of rotation. |
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Static Loaded Radius
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The measurement from the middle of the axle to the road surface; measured with the tire inflated to required pressure and carrying the rated load. |
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Steel Belt
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A belt material used in tires. Its high stiffness provides good handling and low tread wear. |
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Steering Axis
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An imaginary line drawn through the center of the steering pivots. The axis about which the wheel pivots when turned. |
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Steering Response
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Reaction time between driver input at the steering wheel and the directional change of the vehicle. |
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Steering System
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A major control mechanism that multiplies driver input on the steering wheel into the motion of turning a vehicle's front wheels. |
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Sulfur
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A chemical element used in the vulcanization process. |
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Suspension
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A system of devices supporting the upper part (body and chassis) of a vehicle on its axles. |
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Suspension Package
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A specialized kit of suspension components designed specifically for individual makes and models of vehicles; usually sold to improve performance. |
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Swing Axle
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A rear suspension system comprised on half shafts with universal joints only at their inward ends on either side of the differential. |
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Swing Out
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The tendency of the rear tires of a vehicle to break away during sudden steering maneuvers. |
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Synthetic Rubber
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Rubber made from chemicals as a substitute for natural rubber; properties can be tailored for specific needs. |
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