Tyre Codes. What do they mean?

Everyone has noticed the markings, or tyre codes, on the side of their tyres, but I suspect very few of us know what they mean.

We normally have the tyres checked as part of the process for registration and greenslip renewal, so it is good to understand the codes

When your tyres are being replaced you should check the code on the side of the tyre.  The numbers on the side of a tyre are part of a code system.

A common specification for an Australian car tyre is as follows:

205 / 65R15 95H

The code for that tyre can be interpreted as follows:

  • 205 – Width of the tyre in millimeters.
  • 65 – Height of the tyre as a percentage of the width.  Height is measured at the side of the tyre, from the rim to the top of the tread.  Low profile tyres have a low height and will therefore have a lower percentage.
  • R – Radial ply construction.
  • 15 – Diameter of the rim in inches.
  • 95 – Load ratings index.
  • H – Speed symbol.

The load ratings index and speed symbol need to be read in conjunction.  The numbers indicate the maximum load and speed at which the tyre can operate safely if it is correctly fitted, correctly inflated and in sound condition.

The load ratings are indicated by the following symbols:

Load Index
 Maximum Load per Tyre (kg)
 81  462
 82  475
 85  515
 86  530
 87  545
 90  600
 92  630
 95  690
 96  710

The speed symbols are as follows:

Speed Symbol
Maximum Speed (km/h)
 N 140
 P 150
 Q 160
 R 170
 S 180
 T 190
 U 200
 H 210
 V 240
 Z 240
 W 270
 Y 300

You should not rely on the load ratings and speed categories above.  You should specifically check the categories used by the tyre manufacturer.

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