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Tyre size calculator

If you are thinking of changing the size of your car tyres, or are planning on buying a new wheel/tyre combination then it is important that you use the tool below to ensure ride height and speedometer ratings don't change drastically. We would also recommend checking the guidelines set out by your car manufacturer and your car tyre manufacturer.

What is my tyre size?

Your tyre size can be found on the sidewall of our existing tyres and is a series of numbers and letters that looks like the diagram below. When looking for your tyre size it is important to note down the size of both the front and rear tyres as many cars have been designed with two different sizes.

Tyre widthWidth of the tyre in millimetres
Tyre profileHeight of the tyre sidewall as a percentage of the width. In this case 65% of 215mm. Also know as the aspect ratio.
Wheel sizeThe diameter of the tyre's inner rim in inches
Load ratingIndicates what weight each tyre is able to carry. In this case 95 on the Load Index is 615kg.
Speed ratingIndicates the maximum speed for the tyre when at full load. In this case H on the Speed Index means 168 mph.

Changing tyre sizes

When considering changing wheel and tyre sizes, it is important to maintain a diameter that is as close as possible to the original so that the gearing of the drive train is not adversely impacted. Doing so will also ensure that the ride height will not change significantly.

Entering your current and desired new tyre size into the calculator below will enable you to see if this is a viable and safe option. If the percentage difference in diameter is more or less than two point five percent we would not recommend this change.

To buy your new tyres online simple enter the correct tyre size into the search tool above and select the best tyre for your needs. Alternatively, if you would like to discuss changing tyre sizes or choosing the most appropriate tyre for your needs you can call our national sales team on 0800 028 9000 seven days-a-week.

Current tyre size
Tyre width:
Tyre profile:
Wheel size:
Overall diameter:
New tyre size
Tyre width:
Tyre profile:
Wheel size:
Overall diameter:
Difference in diameter: 0%Actual diameter change: 0mm
We recommend a MAXIMUM of +/- 2.5% difference
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