Old Town Autos

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Some Frequently Asked Questions

Q:  What do tyre size measurements mean?

The tyre size is made up of 3 measurements, the width, the profile and the diameter.

In the example image here the width is 275, the profile is 45 and the diameter is 21.

The width is the nominal width of the tyre in millimetres. The profile is the side wall height calculated as a percentage of the width of the tyre (e.g. 45% x 275mm).  The diameter must match the diameter of the wheel, and all cars have recommended tyre sizes when upgrading from your original wheels to new aftermarket alloy wheels.  

Visit our Tyre Information page HERE or you can visit a handy wheel/tyre size calculator HERE 

Q:  How do I know what speed rating I require?

This is the maximum speed that the vehicle with the tyres fitted to can be safely driven at. It is a code that relates to a set speed in mph/kph. Please see the table below for reference which shows the speed rating code that corresponds to the speed in mph/kph:

Q:  What is the Load Rating?

This is defines the maximum load that the tyre can carry, which needs to meet or exceed half the maximum axle load of the vehicle. If the vehicle has maxmium axle loads of Front 1200 kgs / Rear 1250kgs then this means the front tyres need a tyre load index of 90 or higher (1200kgs / 2 = 600kgs = 90 Index), whereas the rear tyres need 92 or higher (1250kgs / 2 = 625kgs = 92 Index). If you are fitting the same tyres front and rear then the load index needs to be the higher of the two to cover both axles, which would be 92 in this example.

Here is a table to show which load index numbers (from the tyre side wall markings) correspond to the maximum load in kilograms (kgs):

Neil Bennett
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