Car tyre sizes explained

What are tyre sizes? Let’s take the tyre above as an example. The first number is the width of the tyre in millimetres. Therefore, this radial tyre has a width of 205mm.

The ‘65’ confirms the height shown as a percentage of the full tyre width.

The letter ‘R’ depicts the variety of tyre. This refers to the tyre being a radial type- this is like the majority of the tyres used today. The next number shown is the tyre’s height, but this is expressed as a ratio rather than a measurement.

When it comes to how to read tyre size, the first five digits of the code are the ones to concentrate on. In the example above, the tyre is 195mm wide. The two digits following the first slash are what is known as the aspect ratio.

Although the numbers are on the sidewall, very few people know how to decipher them.

When buying new tyres you should only go for ones that have these same numbers to ensure a good fit. The following two numbers (“55”) represent the aspect ratio – or measurement of the sidewall height (in mm). Essentially, this is the ratio of the tyre’s cross-section to its width.

So, in the above example, a tyre that has an aspect ratio of would have a height equal to per cent of its width. Regular road cars generally have wheels that are between and 19inches in diameter, with newer, more sporty , and luxury cars generally having the larger sizes. Where you see the wheel size written down such as 7x17in the larger of the two measurements will virtually always be diameter, with the smaller number relating to the width. Deciphering The Code. The main piece of information is the size of the tyre.

There are many different variations, but in the UK, the most common dimensions. The R in the tyre marking indicates that this is a radial tyre. Tyre Width And Aspect Ratio. Use our tyre size calculator to calculate the diameter, width, sidewall, circumference, and revolutions per mile of any tyre. Just type in a metric or standard size tyre and click calculate.

Inch measurement tyres are fairly easy to understand however metric tyres use a more difficult system to read. Primary Navigation Mobile – Cars. This is always referred to in inches, and as the name suggests is the diameter of the wheel – not the tyre and.

Again this is measured in inches. The width of the wheel dictates what tyres you can fit to the car – The wider. Aftermarket Wheels.

If a tire size has no letters at the beginning, this indicates a Euro metric tire. P-Metric and Euro-Metric tires may have different load capacities. Vehicle manufacturers equip some light trucks with LT type tires. When changing a tyre size , you should ensure that the tyre and wheel assembly diameter of the same value so that the speedometer and gearing remain unchanged.

For each 10mm boost to tyre width, a reduction of in the height of the sidewall is necessary, if the wheel size is unchanged. The size of a tyre is printed onto the side of the tyre – on the area known as the sidewall. A massive tire size chart with both metric and inch tire sizes listed to easily compare every tire size in one spot. Here are two tire size charts that list every tire by wheel size or by diameter to make your search as simple as possible.

Each metric tire measurement shows both the metric tire size and the inch equivalent. If you are curious, the most common tire size is the R15. An Rtire is fitted with a 15-inch rim. The P tire variant is the most common Rtire. The sidewall of a tyre is stamped with codes and markings that will tell you all you need to know about it in order to assess its suitability for your car.

Your tyre size can be found on the sidewall of your current tyre and is a sequence of numbers and letters.