Tyre Tips

Top 10 Tyre Tips

  1. All tyres slowly deflate over a period of time, therefore tyre pressures should be checked every 2-3 weeks.
  2. Tyre pressures should only be checked when they are cold. Your vehicle’s recommended tyre pressures are located on a placard usually on the inside edge of the driver’s door.
  3. Although the minimum amount of tread required for a car to be roadworthy is 1.6 mm, it’s wise to replace tyres at 2 mm, as wet-weather grip is diminished when there is only a small amount of tread.
  4. To check tread depth, put a match head into the tread grooves, and if any part of the head shows above the grooves it’s time to replace the tyre. Tyre tread depth checks are also available from any Autowiel branch for free
  5. Regularly check tyres for wear such as tears or bruises on sidewalls as well as embedded objects like nails or stones as they may lead to a puncture.
  6. To keep water and dirt out of tyre valves replace missing tyre valve caps.
  7. And most importantly with all these checks…don’t forget the spare!
  8. Regular wheel balances ensure your tyres run smoothly on the road which helps to improve your vehicle’s control, especially on wet roads.
  9. Wheel alignments and rotations maximise the life of your tyres by ensuring your tyres wear evenly.
  10. Match the same tyre treads on the same axle. Different brands grip differently which can cause handling problems if mismatched.

More Tyre Tips


Check all parts, including wheels and studs and mounting faces of hub and wheels, for dirt, rust or damage. Use a wire brush to remove dirt and rust, replace any damaged parts. Careless installation of wheels on a vehicle is a major cause of tire and wheel problems. Proper installation, including nut torque, is essential to safe, economical, trouble free service. Use only the specified sizes and types of studs and nuts.

Tighten the nuts a quarter turn at a time following the criss-cross sequence shown above. This is very important. Failure to tighten the nuts in this criss-cross sequence will cause a misalignment of the wheel. Continue until all nuts are tightened to the manufacturers specified torque.

Improper torque can cause distortion, fatigue cracks or alignment problems. After running the vehicle for a short distance, check the nuts for tightness. Parts will usually seat naturally and torque on nuts will drop. Retighten all nuts to the specified torque.

* The information above is for the tire professional and should not be attempted by individuals not properly trained & equipped.

This information can be found on our 2004 Lug Nut Torque Chart.

Uniform Tire Quality Grading

The Federal Government Uniform Tire Quality Grading Standards (49 CFR 575.104) apply to passenger car tires only (but excludes deep tread, winter-type snow tires, temporary use spare tires, and tires with nominal rim diameters of twelve inches or less). Tires subject to the Standards are required to be graded on the performance factors of treadwear, traction and temperature. The grades are molded on the tire sidewall, and in addition for replacement tires, a label affixed to the tread lists and explains these grades. Tire characteristics defined in the Standards are as follows:

The treadwear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test course. For example, a tire graded 150 would wear one and a half (1 1/2) times as well on the government course as a tire graded 100. The relative performance of tires depends upon the actual conditions of their use, however and may depart significantly from the norm due to variations in driving habits, service practices, and differences in road characteristics and climate.

The traction grades, from highest to lowest, are AA, A, B and C. These grades represent the tire’s ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. A tire marked C may have poor traction performance. WARNING: The traction grade assigned to each tire is based on straight-ahead braking traction tests, and does not include acceleration, cornering, hydroplaning or peak trac- tion characteristics.

The temperature grades are A (highest), B and C, representing the tire’s resistance to the gener- ation of heat and it’s ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tire to de- generate and reduce tire life, and excess temperature can lead to sudden tire failure. The grade C corrosponds to a level of performance which all passenger car tires must meet under the Federal Motor Vehicle Safety Standard # 109. Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law. WARNING: The temperature grade for each tire is established for a tire that is properly inflated and not overloaded. Excessive speed, under inflation or excessive loading, either separately or in combination, can cause heat buildup and possible tire failure.

Alpha Numeric Conversion Chart


IMPORTANT: Do not exceed maximum tire pressure imprinted on tire sidewall.
               AR78-13 P165/80Rl3, P175/75Rl3, P185/70RI3, P195/60Rl3, P215/50Rl3, 185/70Rl3


P175/80Rl3, P185/75Rl3, P195/70Rl3, P195/65Rl3, P205/60Rl3


P185/80Rl3, P195/70Rl3, P215/60Rl3, P235/50Rl3


P175/75Rl4, P185/70Rl4, 185/70Rl4


P185/75Rl4, P195/70Rl4, P205/65Rl4, P215/60Rl4, 195/70Rl4


P185/80Rl4, P195/75Rl4, P205/70Rl4, P205/65Rl4, P215/60Rl4, P245/50Rl4


P195/75Rl4, P205/70Rl4, P225/60Rl4, P245/50Rl4


P225/75Rl4, P235/70Rl4
BR78-15 P165/80Rl5, P175/75Rl5, P185/70Rl5
ER78-15 P195/75Rl5, P215/65Rl5, P245/50Rl5
FR78-15 P205/75Rl5, P215/70Rl5, P215/65Rl5, P235/60Rl5, P245/50Rl5
GR78-15 P215/75Rl5, P215/70RI5, P235/60Rl5, P255/55Rl5, P265/50Rl5
HR78-15 P225/75Rl5, P235/70Rl5, P255/60Rl5, P275/50R15
JR78-15 P225/75Rl5, P235/70Rl5, P255/60Rl5


P235/75Rl5, P245/70Rl5, P255/65Rl5, P265/60Rl5, P295/50Rl5

The information above is for the tire professional and
should not be attempted by individuals not properly trained & equipped


How to Calculate Adjustment Prices

  1. Find the original tread depth in the price sheet/data book.

  2. Using a stick-type 32nds gauge, measure the 32nds of
    tread remaining at three pints in the center two grooves
    and average the three measurements.

  3. Where the averaged tread depth remaining line meets the
    appropriate original tread depth column, the percent of tread
    worn off the tire will be found.

  4. Using this percentage to calculate the customer’s replacement price.

With A Tyre-Marking Crayon, Mark On The Adjustment Tyre:

  1. Location of the service condition (circled)
  2. Adjustment claim number
  3. Retailer name
  4. Rub across the serial number so that it can be seen and easily read

Make sure that the customer
the Customer Section of
the adjustment claim!

Aspect Ratio Section height/section width x 100 – ratio between tire height and width
Asymmetric When opposite sides of a tire’s tread pattern are not identical.
Backside Setting The distance from the mounting surface of the wheel, which contacts the hub, to the back rim flange. It is sometimes referred to as the backspacing or backside measurement.
Balance The even distribution of weight on a mounted wheel and tire.
Bias-Belted Tire A passenger type tire which has two rubberized plies of cords which are crossed over one another at an angle (on a bias) plus two reinforced belts which encircle the tires under the tread.
Block Tread Design A tire tread pattern made of raised rubber compound segments.
Bolt Circle Sometimes referred to as bolt pattern: The number of lug holes on the diameter of the imaginary circle that each lug hole is centered on.
Carcass The portion of a tire that is the foundation for the tread, belts, bead and sidewall.
Casing The structure of tire cords locked around wire beads.
Compound  The general term referring to the chemical formula for the tread material.
Criss-Cross Torquing The recommended sequential tightening of the lug nuts in a pattern across from one another to help ensure even tightening.
Grooves Circumferential channels between and the tread ribs of a tire.
Hub Centric A situation where the center bore of the wheel is made to match up with the diameter of the automobile hubs; the wheel is then balanced by the center hold rather that the lug holes.
Hydroplaning Loss of traction at high speeds caused by a wedge of water that lifts a tire off the road surface.
Load Rating The maximum weight that the tire is designed to carry; dictated by the tire’s construction. Metric passenger type tires are offered with a Standard Load Rating (up to 35 psi), or Extra Load Rating (up to 41 psi). LT Metric (truck type) tires are offered with ply ratings of C (8 ply), D (8 ply), and (10 ply) and at various inflation pressures up to 80 psi.
Low Profile  A term describing a tire with a low relative aspect ratio or series classification (short sidewall, wide tread).
Negative Offset A condition where the wheel’s mounting surface is closer to the inside of the wheel; when the mounting surface is inboard the wheel’s centerline.
Nominal Rim Diameter Diameter of rim seat supporting the tire bead. Examples: 13′, 15″ and 16.5″.
Offset The positive or negative distance from the wheel’s centerline to the mounting surface of the wheel.
Overall Diameter  The diameter of the inflated tire without any load.
Overall Width  Maximum width in cross-section of the unloaded tire including protruding sides ribs and decorations.
Ply  A layer of rubber-coated fabric or wire making up the tire casing.
Positive Offset  A condition where the wheel’s mounting surface is closer to the street side of the wheel; when the mounting surface is outboard the wheel’s centerline.
Radial Ply Tire A type of tire that has one or more rubberized plies of cords running from bead to bead (at right angles to the tread and parallel to each other), plus two or more plies of reinforced belts which encircle the tire under the tread.
Ribs  Part of a tire tread pattern created by grooves that run circumferentially around the tire.
Rim Diameter  The distance between bead seat to bead seat at beat seat radius.
Rim Flange  The edge of the wheel’s rim that the clip-on weights attach to. 
Rim Width  The distance between the inside surfaces of the rim flanges.
Section Height The distance from rim seat to outer tread surface of an unloaded tire.
Section Width The linear distance between the outside sidewalls of an inflated tire without any load (exclusive of protruding side ribs and decorations).
Series A numerical representation of a tire’s aspect ratio; for example, 50 series.
Shoulder Blocks  Raised rubber compound segments on the part of the tire tread nearest the sidewall.
Sipes Slits in the tire tread. Small cuts in the surface of the tread to improve traction.
Steel Belt A belt material used in radial tires. Its high stiffness provides good handling and low treadwear.
Tire Profile A term representing the portion of a tire measured as its aspect ratio or series.
Tread Blocks Raised rubber compound segments on the outside visible part of a tire.
Tread Width  The portion of the tread design that comes in contact with the road.
Unsprung Weight  The total weight of the automobile’s components not supported by the suspension system; wheels and tires are prime examples.
UTQG Uniform Tire Quality Grade – A government-mandated tire rating system based on a tire’s performance in treadwear durability, traction, and temperature resistance. UTQG ratings are branded on the tire’s sidewall.
Varied-Pitch Ratio Variations of angles and sizes of a tire’s tread elements that reduce ride noise levels.
Zero Offset A condition where the wheel’s mounting surface coincides with the centerline of the wheel.


ASPECT RATIO = Section Height  xl00
Section Width  

DEFLECTION = Free radius minus loaded radius.  

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

LOADED RADIUS = Distance from wheel axis of rotation to supporting surface at a given load and stated inflation pressure. 

LOADED SECTlON HEIGHT = The loaded radius minus half of the nominal rim diameter. Distance from rim seat to outer tread surface of a loaded tire. 

NOMINAL RIM DIAMETER = Diameter of rim seat supporting the tire bead. Examples: 13″, 15″ and 16.5″.  

OVERALL DIAMETER = The diameter of the inflated tire without any load.  

OVERALL WIDTH = Maximum width in cross section of unloaded tire including protruding side ribs and decorations. 

REVOLUTIONS PER MILE = Measured number of revolutions for a tire traveling one mile. This can vary with load and inflation. 

RIM WIDTH = Linear distance between rim flanges in contact with the tire. 

ROLLING CIRCUMFERENCE = The linear distance traveled by a tire in one revolution. 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.

SECTION HEIGHT = Distance from rim seat to outer tread surface of unloaded tire.  

SECTION WIDTH = Linear distance between the outside sidewalls of an inflated tire without any load (exclusive of protruding side ribs and decorations). 

TREAD WIDTH = The portion of the tread design which comes in contact with the road.


Forward or backward tilt of king pin or
spindle support arm at the top.

Measured in degrees positive or negative.

Influence on Vehicle Handling:

Too little causes high-speed instability and
poor directional stability such as wandering.

Too much causes hard steering, excessive road shock, and shimmy through the steering wheel.

Influence on Tire Wear:

Usually not a factor in tire wear.


Inward or outward tilt of wheel at the top.
Outward is positive, inward is negative.

Measured in degrees positive or negative.

Influence on Vehicle Handling:

Excessive camber (negative or positive) will cause vehicle to pull to the side with greatest variance.

Influence on Tire Wear:


Amount that front of wheels is closer together than rear of wheels.  For radial tires, toe should be as close to “0” as possible when vehicle is running.

Measured in inches.

Influence on Vehicle Handling:

May cause vehicle to track improperly and
steering wheel to be off centered.

Influence on Tyre Wear:


Feather Edge
Pointed In


Feather Edge
Pointed Out

Incorrect toe will cause a feather-edge
wear pattern across the tire tread that
can be felt as you slice your hand
across the tread.


Inward tile of spindle support arm
or king pin at the top.

Directional control angle measured in degrees that spindle support center line
is tilted from true vertical.

Influence on Vehicle Handling:

Non-adjustable angle that, with camber, controls “scrub radius” to minimize
effects of road bumps on steering.

Influence on Tire Wear:

Rapid tire wear can result from mounting new wheels with different offset that may increase scrub radius by moving tire footprint outside projected pivot point.


Amount that front wheels tow out during turns.  Ideal angle reduces tire scrubbing.

Measured in degrees.

Influence on Vehicle Handling:

Does not influence vehicle handling qualities.

Influence on Tyre Wear:



  • Improper alignment (TOE)
  • Worn or damaged steering
    and/or suspension parts
  • Hard cornering
  • Check/correct alignment
  • Check/replace steering and/or suspension parts
  • Based on tread depth rotate/replace tire


  • Worn or damaged steering and/or suspension parts
  • Improper balancing
  • Check/replace steering and/or suspension parts
  • Check/correct balance
  • Check/replace wheels
  • Based on tread depth rotate/replace tire


  • Improper alignment (CAMBER)
  • Worn or damaged steering and/or suspension parts
  • Check/correct alignment
  • Check/replace steering and/or suspension parts


  • Center wear – over inflated
  • Both edges – under inflated
    slow leak
  • Adjust air pressure
  • Check fitment
  • Check/correct air leak


How Accomplished

Support Vehicle Load
  • By containing compressed air in a sealed chamber.
  • Higher air pressure supports higher loads.
  • Larger air chamber size support higher loads.
Absorb Shocks from Road Surface
  • Like a spring, with a shock absorbing quality and the ability to reduce unnecessary motion.
  • The more compressed vertically, the more protection provided for the vehicle.
Transmit Traction and Braking Forces to the Road Surface
  • Through the footprint’s ability to conforms to road surface irregularities and provided high friction.
Change and Maintain Direction
of Travel
  • Through the footprint to provide straight-line stability and tractive forces in response to steering input.


  1. Grooves
    Channels for water evacuation between tread and road surface.

  2. Ribs
    Circumferential bands of tread rubber between grooves for continuous road contact and traction, may be enhanced with sipes.

  3. Tread
    Contact area with road surface using various compound strategies like maximizing grip or mileage.

  4. Shoulder
    Transition element between tread and sidewall for traction during cornering and maneuvering.

  5. Belts
    Woven steel cord mesh for rigidity of tread rubber to reduce tread squirm and increase tread life.

  6. Undertread
    Compounded for high heat resistance to increase high-speed durability and sometimes fuel economy.

  7. Inner Liner
    Special rubber compound highly impervious to air migration for maintaining air pressure without leaking.

  8. Body Plies
    Either fabric cord (passenger and lgi8th truck tires) or steel cord (mainly truck tires) for structural strength of air chamber.

  9. Bead Cable
    Rigid cable serving as an anchor around which body plies are wrapped and which secures tire to rim flange area.

  10. Bead Apex/Filler
    Special hard rubber compound extending up into sidewall to increase flexing around bead cable and enhance stiffness of lower sidewall for improved handling.

  11. Bead Chafer
    Layer of fabric material protecting bead area from rim chafing and mounting damage.


Wheel Dimensions

  • Wheel Width: Distance between inside of flanges rounded to nearest 1/2″.  Ensure that wheel width is proper for tire size you intend to mount on it. All tire sizes have minimum and maximum wheel width limits.

  • Wheel Diameter: Distance from bead seat to bead seat across diameter of wheel.  Must be exactly the same as tire rim diameter.  Always check diameter stamped on the wheel and match the tire exactly.

  • Wheel Offset: Distance between wheel mounting surface where bolted to hub of drum and centerline of rim.  Determines vehicles “track” or distance between tires on each axle.  Keep the wheel offsets as close to original as possible to avoid steering difficulties or wheel bearing fatigue.