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Tyre inflation pressure

To get the most life and performance out of your tyres, keep your tyres inflated at the right pressure. Incorrect pressure changes the contact your tyre has with the road. This results in impaired handling and braking.

What’s the difference between under and over inflated tyres?

Under-inflation can cause:

  • Excessive tyre flexing and heat which can lead to failure or ‘blow out’
  • Accelerated tyre wear
  • Uneven wear patterns
  • Heaving steering
  • Increased fuel consumption

Over-inflation can cause:

  • Uneven wear patterns
  • Increased risk of tyre impact damage
  • Harsh ride

To keep your pressure more stable, nitrogen gas may be recommended to inflate your car tyres.

What’s the right tyre pressure for my car?

All cars built since 1973 have a tyre placard located either in the glove box, driver’s door, inside the fuel cap or under the bonnet of your car. The placard lists information on the original tyres and their correct inflation pressure. You can find this in your owner handbook too.

What’s on the tyre placard?

  • Minimum allowable cold pressures
  • Pressure shown in Kilopascals (kPa) and often in pounds per square inch (PSI). 

Conversion = 7kPA = 1PSI

Tyre placard shows correct pressures

Tips to remember when checking your tyre pressure

  • You can inflate your tyres to the max numbers shown on the placard
  • Check tyre pressure when your tyres are cold
  • Don’t bleed air from hot tyres
  • Replace the valve dust caps after checking tyre pressure
  • Increase tyre pressure if you’re carrying an increased load or you’re driving at high-speed
  • Complete fortnightly pressure checks with your own tyre gauge
  • If you notice a pressure drop, especially in one tyre, it’s worth getting it checked for a puncture or defective valve

The importance of wheel alignments

Wheel alignments help your tyres last longer, reducing your number of tyre replacements. When you’re checking tyre pressure it’s a good idea to look for uneven tread as this can indicate misaligned wheels. If you notice an uneven tread pattern, have a chat to your mechanic or tyre dealer. Regular tyre rotation is recommended to extend the life of your tyres and increase tyre safety.

Understanding tyre markings

The markings on tyres provide lots of information on the type, loadings and dimensions of your tyres.
Tyre marking on sidewall

A – The brand, make and model of the tyre

B – Section width

These three numerals show the tyre width in millimetres. This is the total inflated width at its widest point (excluding sidewall ribs and lettering). The ‘P’ indicates this is a tyre for a passenger car

Cross section of tyre

C – Aspect ratio

This number shows the height of the tyre by expressing it as a percentage of the section width. A P205/60 tyre shows the section width is 205mm and the height is 60% of that. The lower this number, the lower the tyre profile. The typical ratio is between 50 and 75, although high performance tyres can go as low as 30.

D – Construction

This single letter shows the type of construction. R stands for radial, B for Bias.

E – Rim

This number represents the rim diameter which fits the tyre. This measurement is always in inches.

F – Load

This number is checked against a chart to identify the maximum load the tyre can carry at the speed indicated.

G – Speed

This symbol is determined by the maximum safety speed. Passenger tyre speed ratings start at N (140km/hr) and go through to Y (300km/h).

If you'd like peace of mind that your tyres will last the distance, an RACQ Vehicle Inspection can help you out.Call us on 13 1905.