Wheels and Tires Terminologyy

Glossary of Wheels and Tires Terminology

Tire related term MeaningA

Anti-Lock Brake System (ABS)

Under emergency braking using conventional braking systemsthe wheels can lock up, making the car un-steerable. ABSsystems provide continuous monitoring and control of thebraking force and in some circumstances can reduce thebraking distance while maintaining full car steer ability.

Anti-ozidant

Specialized chemicals designed to retard ozone contaminationof rubber preventing premature aging, brittleness andretention of suppleness and pliability.

Anti-slip-control (ASR)

ASR is fitted to vehicles to prevent wheels slipping, spinningon slippery or uneven surfaces.

Aging Rubber degrades when exposed to heat, oxygen, ozone, andother elements.

Air Pressure The amount of air inside the tire pressing outward on eachsquare inch of tire, which is expressed in pounds per squareinch (psi) or kiloPascals (kPa), the metric designation for airpressure.

Airtight Synthetic Rubber Formulated with virtually impermeable butyl rubber, thismaterial replaces the inner tube in modern, tubeless tires.Check you air pressure monthly, as some air loss occurs overtime.

Alignment

When all wheels on the vehicle are adjusted so that they arepointed in the optimum direction relative to the road and eachother.

All-season tires Tires that provide a good balance of traction in rain or snowwith good tread life and a comfortable, quiet ride.

Alphanumeric

A term for describing the size of a tire (H78-15, for example)where both letters and numbers are used.

Aquaplaning An extremely dangerous situation where water builds up infront of the tires resulting in the tires losing contact with theroad surface. At this point, the vehicle is skimming on thewater surface and is completely out of control. Also calledhydroplaning.

AspectRatio

The relationship of a tire’s sidewall height to its section width.

BBalance/Imbalance

The state in which a tire and wheel spin with all their weightdistributed equally. To correct an imbalance, a trainedmechanic will add weights on the interior or exterior of the

http://www.thecartech.com/KnowYourCar/Wheels_tires/Wheels_and_tire...

1 of 16 10/26/2013 1:22 AM

wheel.Bearing An anti-friction device that commonly uses balls or rollers

held between inner and outer races. Designed to reducefriction between moving parts while providing support for theshaft. Common types of bearings are roller bearings and ballbearings.

Belt

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

Belt Wedge A tire component used by most manufacturers to preventtread separations. A belt wedge is a piece of rubber insertedinside the tire at the belt edges.

Bead The part of the tire that is made of steel wires. Wrapped orreinforced by ply cords and that is shaped to fit the rim.

Bias ply tire A pneumatic tire in which the ply cords that extend to thebeads are laid at alternate angles substantially less than 90degrees to the centerline of the tread.

Bleeding a tire Releasing air to reduce pressure in tire.Blowout

A bursting of a tire and inner tube., usually associated with aloud popping noise.

Braking distance

The distance required for braking depends on the speed of thevehicle, the condition of the road surface and the condition ofthe tires, in particular the tread. Check the tires tread depthregularly and change your tires when worn down to the "treadwear indicators" located at the bottom of the tread grooves.

CCamber

A wheel’s inward or outward tilt from vertical, measured indegrees. The camber angle is adjusted to keep the outsidetires 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 tiregenerates.

Carbon Black

This is a reinforcing filler which, when incorporated into thetire rubber compound, gives it a high resistance to wear.


2 of 16 10/26/2013 1:22 AM

Carcass (Casing) The tire structure, except tread and sidewall rubber which,when inflated, bears the load.

Carrying Capacity

At a given air pressure, how much weight each tire isdesigned to carry. For each tire size, there is a load inflationtable to ensure the inflation pressure used is sufficient for thevehicle axle load.

Caster The angle between a line drawn vertically through a wheel’scenterline 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. Alignmenttracking is measured from this line.

Centrifugal Force

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

Chains

Even modern winter tires can sometimes not help when thereare huge amounts of snow and steep gradients. In thesesituations traction, lateral control and reliable braking requiretire chains

Chunking The breaking away of pieces of the tread or sidewall.Comfort

Indicates the tires ability to minimize road noise, harshness,and vibration as perceived by the vehicle occupants.

Contact Patch The area in which the tire is in contact with the road surface.Also called footprint.

Cord The strands forming the plies in the tire.Cord separation The parting of cords from adjacent rubber compounds.Cornering Force

The force on a turning vehicle’s tires - the tire’s ability to gripand resist side force - that keeps the vehicle on the desiredarc.

Cracking Any parting within the tread, sidewall, or innerliner of the tireextending to cord material.

Crown Section between shoulders of the tires.Curb Weight

Weight of a production vehicle with fluid reservoirs (includingfuel tank) full and all normal equipment in place, but withoutdriver or passengers.

Cure To vulcanize; also time and temperature conditions used tovulcanize a tire.

DDate of Manufacture The date of manufacture of a tire is indicated on the tire's


3 of 16 10/26/2013 1:22 AM

sidewall at the end of the DOT serial number.

Deflection

The tread and sidewall flexing where the tread comes intocontact with the road.

Direction ofRotation

On standard tires with symmetrical tread patterns, it does notmatter which way the tire is fitted on the rim and in whichposition it is fitted on the car.Some tire manufacturers have, however, started producingtires with specific directions of rotation in order to improvewet grip and optimize noise generation.The direction of rotation is marked on the side of the tire withan arrow. This side of the tire must be on the outside, and thetire must roll forwards in the direction of the arrow foroptimum tire performance.

Directional Stability

The ability of a vehicle to be driven safely and withconfidence in a straight line and at high speed without beingaffected by pavement irregularities, crosswinds, aerodynamiclifting forces, or other external influences.

Directional tread

Tread design in which performance is dependent upondirection of rotation.

Dog Tracking

Track is the width between the outside tread edges of tires onthe 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 frontwheels when the vehicle is traveling in a straight line. Alsocalled tracking.

DOT Markings A code molded into the sidewall of a tire signifying that thetire complies with U.S. Department of Transportation motorvehicle safety standards.

Drift

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

Duals Tires placed side by side on an axle to increase both carryingcapacity and traction capability; four tires across an axle.

Dynamic Balance

Exists when the weight is equally distributed both around itscircumference and on either side of its centerline. A tire andwheels assembly that is out of dynamic balance will produce awobble effect or a shaking from side to side.

FFlat spot Irregular wear in an isolated spot or spots around the tire

tread. Flat spotting can also result from abrasion of the tireresulting from brake lock.


4 of 16 10/26/2013 1:22 AM

Footprint

The portion of the tire that makes contact with the surface ofthe road.

Fore-and-Aft Weight Transfer

Transfer of weight from the front axle to the rear axle (or viceversa) caused by acceleration or braking. Acceleration causesweight transfer from the front axle to the rear axle. Brakingcauses weight transfer from the rear axle to the front axle.

Free Radius

The radius of the tire/wheel assembly that is not deflectedunder load.

Friction

The resistance of one material (the tire tread) as it movesagainst another (the road); this is the force that causes the tireto grip to the road.

GGreen Tire A tire which has not been vulcanized or cured.Groove The space between two adjacent tread ribs.

Gross Axle Weight Rating (GAWR) The maximum weight that can be distributed among the tireson 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 canbe identified on the vehicle door placard.

HHydroplaning

Is what happens when tires lose traction as a result of worn orpoorly treaded tires that can no longer effectively evacuatewater away from the tread. Water accumulates under the tirefootprint and creates a thin layer of water between the tireand road surface. The resulting pressure pushes upward, thuslifting the tire away from the road surface and causing it tolose traction. Vehicle speed, tread pattern and water depth allaffect hydroplaning.

Hysteresis

When rubber stretches and compresses, it does not render allthe energy applied to it because energy is lost due to internalfriction. The mechanical energy is transformed into thermalenergy and the heat produced leads to both damage andenergy loss.

IImbalance

The condition that exists when a tire's mass is not evenlydistributed around the rolling axis and centerline, causingbounce (static imbalance) or shake (dynamic imbalance).

Inflation The act of putting air into tires.Cold tire inflation pressure Tire pressure when the vehicle has been parked for three

hours or more, or has not been driven more than 1 mile or 1.5km under that condition.

Maximum inflation pressure The maximum cold inflated pressure to which a tire may beinflated, shown on the sidewall of the tire.


5 of 16 10/26/2013 1:22 AM

Recommended inflation pressure Cold tire inflation pressure recommended by the carmanufacturer.

Innerliner The layer(s) forming the inside surface of a tubeless tire thatcontains the inflating medium within the tire.

Innerliner separation The parting of the innerliner from cord material in the carcass.K

Kilopascal (kPa) The metric unit for air pressure. One psi is equal to 6.9 kPa.L

Lateral weight transfer

When a vehicle travels through a curve, weight is transferredfrom the wheels on the inside of the curve to the wheels onthe outside of the curve. This is a result of the centrifugalforce, or lateral force acting on the vehicle.

Light truck

Automotive industry term for smaller trucks, pickups,passenger vans, or SUVs.

Loaded radius

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

Load rating The maximum load that a tire is rated to carry for a giveninflation pressure.

Low profile tire A tire in which the cross-section has a squat appearance. Lowprofile refers to the fact that the tire's cross-section height isless than 80% -85% of the section width.

Maximum load ratingLoad-carrying capacity

The load rating for a tire at the maximum permissible inflationpressure requirements.

Loaded section height

The height of the section of the tire that is making contactwith the road.

Load index

An assigned number ranging from 0 to 279 that correspondsto the load-carrying capacity of a tire.

Lug nut A lug nut is a fastener, specifically a nut, used to secure awheel on a vehicle.

Lug wrench A lug wrench is the name for a type of socket wrench used toloosen and tighten lug nuts on automobile wheels. In theUnited Kingdom, this tool is commonly known as a wheelbrace or wheel wrench.

MM+S, M/S orM & S

All-season rating designation for tires that can perform atcertain levels in mud and snow conditions. Meets the RubberManufacturers Association (RMA) definition of a mud andsnow tire.

Mounting

This is the act of putting a tire on a wheel and ensuring thatthe assembly is balanced. When you purchase new tires, theyneed to be professionally mounted.

NNegative camber

Alignment setting where the tops of the tires are leaningtoward the centerline of the vehicle; racers use a negativecamber angle for maximum cornering potential.

OOE and OEM

OE means "Original Equipment" and refers to the tiresincluded with a new vehicle at the time of purchase. Thevehicle's manufacturer selects these tires to provide the


6 of 16 10/26/2013 1:22 AM

optimal performance based on the performancecharacteristics of the vehicle. "OEM" stands for "OriginalEquipment Manufacturer."

Offset

The distance between the plane of the hub-mounting surfaceof a wheel to the centerline of the wheel and tire assembly.Almost always measured in millimeters, a wheel offset can bepositive, zero or negative.

Open splice Any parting at any junction of tread, sidewall, or innerlinerthat extends to cord material.

Out-of Round A wheel or tire defect in which the wheel or tire is not“perfectly” round. This usually results from a mistake orengineering problem in the tire manufacturing process.

Outer diameterOverall diameter

The overall diameter of an inflated new tire, without any load.

Overall width The linear distance between the exteriors of the sidewalls ofan inflated tire, including elevations due to labeling,decorations, or protective bands or ribs.

Oversteer

The tendency for a vehicle, when negotiating a corner, to turnmore sharply than the driver intends. The rear end of thevehicle wants to swing toward the outside of a turn. Ahandling condition in which the slip angles of the rear tires aregreater than the slip angles of the front tires. An oversteeringcar is sometimes said to be “loose,” because its tail tends toswing wide.

PPassenger car tire A tire intended for use on passenger cars, multipurpose

passenger vehicles, and trucks, that have a gross vehicleweight rating (GVWR) of 10,000 lb. or less.

Plus-sizing

An option allowing drivers to customize their vehicles bymounting low-profile tires on wider rims (one or two inchesgreater in diameter), usually enhancing vehicle appearance,handling, and performance.

Ply A layer of rubber-coating parallel cords.Ply Rating This letter indicates the load carrying capacity of the tire in

terms of its construction. A "C" indicates the tire has a 6-plyload carrying capacity. The tire is not actually built with 6plies, but contains one or two plies of equivalent strength. A"D" is an 8-ply rating, and an "E" is a 10-ply rating. If there isno letter, the tire has a standard 4-ply rating.

Ply separation A parting of rubber compound between adjacent plies.P-metric

Uniform designation of tire sizes, in metric measurementsoriginally introduced by American tire manufacturers in 1977;commonly called P-metric series. A typical P-metric tire isP205/70R14 93S.

Pneumatic tire A tire designed to be filled with air.


7 of 16 10/26/2013 1:22 AM

Positive camber

Alignment angle that makes the top of the tires farther apartthan at the bottom; tires are tilted out from the centerline ofthe vehicle.

Positive caster

Alignment setting when the steering axis is inclined rearwardat the top.

Pressure build up Increase of air pressure in tire caused by temperature rise oftire.

PSI

The most common measurement unit for tire pressure thatstands for pounds per square inch. PSI is intended to measurethe force exerted by the air inside a tire.

Pull .

A condition in which a vehicle swerves to one side withoutbeing steered in that direction, as a result of irregular tirewear, improper front and/or rear wheel alignment, or worn orimproperly adjusted brakes

Puncture Any penetration of a tires air chamber by a foreign object,nail, glass, etc. resulting in the loss of air. Such loss can berapid with the collapse of the inner tube.

RRadial Ply tire A pneumatic tire in which the ply cords that extend to the

beads are laid at substantially 90 degrees to the centerline ofthe tread.

Recap Another term for a retreaded tire.Replacement tire Any tire other than those sold as original equipment.Retreading

Refers to the practice of applying new tread to a used tirecasing. Most commonly used on medium and heavycommercial trucks.

Revolutions Per Mile (RPM)

Also called rpm. Measured number of revolutions for a tiretraveling one mile. This can vary with speed, load, andinflation pressure.

Ribs

A pattern of tread features aligned around the circumferenceof a tire. There are usually multiple ribs across the tread areaof a tire.

Ride height The distance from the ground to a fixed reference point(differs by automaker) on the vehicle’s body. This dimensioncan used to measure the amount of suspension travel or theheight of the body from the ground.

Rim A metal support for a tire or a tire and tube assembly uponwhich the tire beads are seated.

Rim diameter(wheel diameter)

Nominal diameter of the bead seat.

Rim Drop

Also called drop center, a change (drop) in the rim profilebetween the rim flanges in which the bead area of a tire isplaced during the mounting process. This allows the tire to bemounted on the rim.

Rim flange

Surface of the rim of the wheel that contacts the side of thetire bead.

Rim size designation Rime diameter and width


8 of 16 10/26/2013 1:22 AM

Rim type designation The industry manufacturer’s designation for a rim by style orcode.

Rim width Nominal distance between rim flanges.

Rolling circumference

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

Rolling resistance

The force required to keep a tire moving at a uniform speed.The lower the rolling resistance, the less energy needed tokeep a tire moving.

Rotation The changing of tires from front to rear or from side to side ona vehicle according to a set pattern; provides even treadwear.Rotating your tires on a regular basis (every 6,000-8,000miles) is a simple way to add miles to their life. See your tirewarranty for more information on recommended rotation.

Run Flat Technology .

Tires that are designed to resist the effects of deflation whenpunctured, and to enable the vehicle to continue to be drivenat reduced speeds and for limited distances

Runout

The amount a wheel moves in and out, away from its truecenter as it is rotated. If runout is excessive, the wheel can beseen to wobble as it rotates.

SSection height The height of a tire, measured from its rim to its outer tread.

Section width The linear distance between the exteriors of the sidewalls ofan inflated tire, excluding elevations due to labeling,decoration, or protective bands.

Self-aligning torque

When the tire is cornering, torque created at the road contactpatch acts at a point somewhat to the rear of the actual wheelcenter due to pneumatic trail. This has the same effect aspositive caster and tends to force the wheel back to thestraight-ahead position.

Semi-Pneumatic Tires Rubber tires that have a hollow center, but do not usepressurized air for structural support.

Series

Tires with the same aspect ratio, or relationship of sectionheight to section width.

Service description

Numbers and letters molded into the sidewall indicating theload-carrying capacity, load index, and the speed at which thetire can carry a load under specified conditions, or the speedrating. Also known as load index and speed symbol.


9 of 16 10/26/2013 1:22 AM

Shimmy

Wobbling of wheels from side-to-side on a vehicle.Shimmying can be caused by a variety of factors, includingimproperly balanced tires, poor alignment, and bent wheels.

Shock absorber A fluid type cylinder which stops the car from bouncing afterthe initial shock has been absorbed by the spring. Most carshave four shock absorbers.

Shoulder The area of a tire where the tread and sidewall meet.

Sidewall That portion of a tire between the tread and bead.

Sidewall separation The parting of the rubber compound from the cord material inthe side wall.

Singles One tire mounted on each side of an axle (two tires per axle).Sipes

Special slits within a tread block that open as the tire rolls intothe contact patch then close, breaking the water tension onthe road surface and putting rubber in contact with the road tomaintain adhesion, increasing wet and snow traction.

Size

The combination of tire width, construction type, aspect ratio,and rim size used in differentiating tires.

Skid To slip or slide on the road when tires lose their rolling grip.Slip

The difference between the linear speed of the vehicle andthe rotational speed of the tire. For example, if a tire is lockedand sliding (e.g., not rotating) while the vehicle is still moving,then it is operating at -100% slip.

Slip angle The difference between the direction the wheel is travelingand the direction the vehicle is traveling.

Solid Tires Rubber tires similar in construction to semi-pneumatic tires,but without a hollow center.

Speed rating

An alphabetical code (A-Z) assigned to a tire indicating therange of speeds at which the tire can carry a load underspecified service conditions.

Spider wrench Spider wrench, is made in the shape of a cross with differentsized sockets on each of the four ends. It used to loosen andtighten lug nuts on automobile wheels.


10 of 16 10/26/2013 1:22 AM

Sprung weight The parts of a car that are supported by its springs, includingthe frame, engine and body.

Stability Situation in which the driver maintains control of the vehicle.Staggering

A staggered fitment is putting larger wheels on the back ofyour vehicle than the front of your vehicle.

Standard load

The amount of weight a given size tire can carry at arecommended air pressure.

Star pattern A pattern for tightening the lug nuts when mounting the tireand wheel assembly to the vehicle. This pattern assuresuniform pressure, prevents misalignment, and helps keep thewheel centered.

Static balance

Exists when the weight mass is evenly distributed around theaxis of rotation. Static imbalance can be detected fromvibrations through the seat, floor and steering column.

Static loaded radius

Distance from the wheel axis of rotation to supporting surfaceat a given load and stated inflation pressure.

Steel belt

The combination of steel cords covered with rubber thatforms a strip or belt placed under the tread rubber and on topof the casing (carcass); ensures uniformity when the tire isrotating and helps prevent flats.

Steering response

A vehicle’s reaction to a driver’s steering inputs. Also thefeedback that drivers get through the steering wheel as theymake steering inputs.

Steering system

The entire mechanism that allows the driver to guide anddirect the vehicle; includes the steering wheel, steeringcolumn, steering gear, linkages, and wheel supports.

Suspension

The various springs, shock absorbers and linkages used tosuspend a vehicle’s frame, body, engine, and drivetrain aboveits wheels.

TTemporary Spare Tires

Temporary spares are designed to carry the same load as thestandard size tire on your vehicle and can be applied to anyposition. Maintain the proper inflation pressure as shown onthe sidewall of the tire, it requires a higher inflation pressurethan a standard size tire.

Tensile Strength An object’s resistance to stretching or breaking when placedin tension. Steel belts in a tire are characterized and comparedbased on their tensile strength.

Tire

Also called pneumatic tire, a precisely engineered assembly ofrubber, chemicals, fabric, and metal, designed to providetraction, cushion road shock and carry a load under varyingconditions.

Tire Deflection

Situation where the tread and sidewalls flex at the pointwhere the tread comes in contact with the road.

Tire Designation

An alphanumeric code molded into the sidewall of the tirethat describes the tire’s size, including width, aspect ratio, rimdiameter, load index, and speed rating. Most designations use


11 of 16 10/26/2013 1:22 AM

the P-Metric system.Tire Mixing

A situation in which tires of various brands, types, or sizes aremixed on a vehicle. This can lead to variations in the vehicle’sride and handling characteristics.

Tire Placard

A metal or paper tag permanently affixed to a vehicle, whichindicates the appropriate tire size and inflation pressures forthe vehicle. The placard can ordinarily be found on either thedriver’s doorpost, the glove box lid, or the fuel-filler door.

Tire PressureGauge

Tool used to properly measure the air pressure in a tire.

Tire Pressure Monitoring System(TPMS)

TPMS is an automated system that monitors the air pressurein a vehicle's tires. When air pressure in one or more tiresdrops 25 percent or more below the correct pressure, awarning alerts the driver.

Tire Rotation

Process of moving wheels and tires from one position on avehicle to another in order to promote even tire wear andprolong tread life.

Tire Storage

Tires should be stored in a dry, cool place, away from sunlightand sources of ozone.

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

Toe-In

The fronts of two tires on the same axle are closer than therears of the tires.

Toe-Out

The fronts of two tires on the same axle are further apart thanthe rears of the tires.

Toe-Out Turns

Also known as Ackerman Angle. A vehicle’s wheels on theinside of a turn follow a smaller radius than the tires on theoutside of the turn, because the two front wheels steer atdifferent angles when turning.

Torque

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

Torsion Bar

A long, straight bar fastened to the frame at one end and to asuspension part at the other; acts like an uncoiled spring thatabsorbs energy by twisting.

Track

The distance between the outside tread edges of two tires onthe same axle.

Traction

The friction between the tires and the road surface; theamount of grip provided.

Tramping A state in which a vehicle bounces up and down abnormally.Tread That portion of a tire that comes into contact with the road.Tread Blocks

Raised rubber compound segments in a tire’s tread. Blocks ofvarying sizes, shapes, and designs are typically used for avariety of effects, such as better wet traction, or strongerrock-crawling ability.

Tread Buffing Scraping rubber off the tread. Also known as shaving.


12 of 16 10/26/2013 1:22 AM

Tread Depth

The depth of usable tread rubber measured in 32nds of aninch. If a tire comes new with 10/32nds of rubber, you have8/32nds of usable rubber. Tires must be replaced when thewear bars are visible at 2/32nds.

Tread Design

The pattern or layout of grooves, blocks, sipes and other treadelements.

Tread Life The life of a tire before it is pulled from service; mileage.Tread pattern

The arrangement of blocks, grooves, sipes, and channelsdesigned into the tread to enhance its grip. Also called thetread design.

Tread rib A tread section running circumferentially around a tire.Tread separation Pulling away of the tread from the tire carcass.Treadwear indicators(TWI)

The projections within the principle grooves designed to givea visual indication of the degrees of wear of the tread.

Tread Width The width of a tire’s tread.Tread void

Areas in the tread, such as grooves and channels, that permitwater to drain away from the footprint.

Tube An airtight container placed inside tire casing to hold thecompressed air.

Tubeless A tire without a tube.U

Ultra-Low Profile Technology

Specialized sidewall shape, bead area, and bead compoundthat enhance the durability and mountability of tires with veryshort sidewalls.

Underinflation

Operating a tire without sufficient air pressure to support theweight of the vehicle with occupants and additional load;could cause failure of the tire when heat is generated insidethe tire to the point of degeneration of components.

Understeer

The handling characteristic in which the front tires breakloose because they are running a larger slip angle than therear tires. Also known as plowing.

Uni-DirectionalTread

Also known as directional tread, this is a tire designed to onlyrotate in one direction.

Unsprung Weight

The weight of the parts of a vehicle not supported by itssprings, including wheels and tires, outboard brakeassemblies, the rear axle assembly, suspension members,springs, shock absorbers and anti-roll bars.

UTQGS

Also known as Uniform Tire Quality Grading Standards. Agovernment-sponsored tire information system that providesconsumers with ratings (from AA to C) for a tire’s tractionand temperature. Treadwear is normally rated from 60 to 700.

V


13 of 16 10/26/2013 1:22 AM

Valve

A device that lets air in or out of a tire. It is fitted with a valvecap to keep out dirt and moisture, plus a valve core to preventair from escaping.

Valve Cap

The valve cap, although small, has a very important job: itprotects the sensitive valve internals from dust, dirt andhumidity. Without a functional tire valve cap in place, thetires' air will seep out.

Vertical Bouncing

Vertical bouncing, or static imbalance, exists when the weightis not evenly distributed around the wheel’s axis of rotation.You can feel this through the floor, seat and steering column.

Viscous Planing

Can occur just after a rain shower wets down a dry roadsurface. Oil on the road surface migrates to the top of thelayer of moisture, and can be very slippery, even when thelayer of moisture is very thin. Continuing rain lessens thecondition by washing the oil away.

WWander

A vehicle’s tendency to stray or wander from its intendeddirection of travel as a result of steering abnormalities, worntires, suspension misalignment, crosswinds, or pavementirregularities.

Wet traction

Indicates how efficiently the tire disperses water to combataquaplaning, and how well it grips wet roads in low-speeddriving.

Wheel Alignment

Refers to the proper angle settings of suspension componentsas they relate to the angles of the wheels so they areperpendicular to the ground and parallel to each other so as tohelp prolong tire life and provide dead straight tracking onstraight and level roads. Related terms include camber, casterand toe.

Wheel Balancing

Refers to the balancing of a wheel on vertical axis by usinglead weights to compensate for uneven weight distribution ona wheel and tire. Out-of-balance wheels can cause a vehicleto vibrate at certain speeds and produce uneven tire wear.

Wheelbase The longitudinal distance from the center of the front wheelto the center of the rear wheel on the same side of thevehicle.

Wheel Diameter .

The physical diameter of a wheel expressed in inches. Wholeincrements (i.e. 16, 17 or 18) are the most common, however,a few manufacturers offer wheels with diameters of 17.5inches, though this is rare

Wheel weights

Small weights attached or secured to the wheel to balance thetire and wheel assembly.

Wheel Width

The physical width of a wheel measured inside the outer lip ofthe wheel, usually in 1/2 increments (i.e. 7.5 or 8.5).

ZZero Pressure™ Technology

Michelin® Zero Pressure™ tires feature a reinforced sidewallthat is designed to support the weight of your car even after aloss of air pressure — even with no air in the tire. Michelin®Zero Pressure Technology allows you to continue driving up


14 of 16 10/26/2013 1:22 AM

to 50 miles at 55 mph, so you don’t have to change a tire onthe side of a busy highway. Best of all, Zero PressureTechnology has been applied to some of the best-performingMichelin® tires.

Zero toe

When tires on the same axle are parallel; the fronts and rearsof the tires are equidistant.

Tire Construction & dimensions

Tire construc�on

Tire construc�on and dimensions


15 of 16 10/26/2013 1:22 AM

Tire dimensions

Rim dimensions

www.thecartech.com


16 of 16 10/26/2013 1:22 AM

Wheels and Tires Terminologyy

Documents

Transcript of Wheels and Tires Terminologyy