Your tyre size can be found on the sidewall of your current tyre and is a sequence of numbers and letters. The most common tyre size in the UK is 205/55R16 but there are many variations so its important to check your existing tyre first before searching for tyres.
Tyre Width
The first three digits. This displays the width of the tyre in millimetres. A tyre marked 225 will measure 225mm across the tread from sidewall to sidewall.
Aspect Ratio
The fourth and fifth digits of the tyre code that immediately follow the tyre width. The aspect ratio or profile height of the tyre sidewall is expressed as a percentage of the tyre width. So an aspect ratio of 55 for example means that the profile height of the tyre is 55% of its width.
Rim Diameter
The next two digits represent the size of the wheel rim that the tyre can be fitted to. It is also the diameter of the tyre from bead to bead. So a tyre marked 16 will fit on a 16-inch wheel rim.
Speed Rating
The speed rating of a tyre is represented by a letter of the alphabet at the end of the tyre size code and indicates the maximum speed capability of the tyre. Tyres receive a speed rating based on a series of tests which measure the tyres capability to handle a set speed for a prolonged period of time.
Select your tyre speed rating to find out the maximum speed your tyres can maintain.
If you are unsure what speed rating you need, be sure to check your vehicle handbook. Choosing a lower speed rating than that recommended by your vehicle manufacturer could potentially invalidate your insurance.
Load Rating
The load index provides information on the maximum weight capability for the tyre. The load index is a numerical code that can be located just after the tyre size marking and before the speed rating.
Select your load index to find out the maximum load capability for your tyres.
Although not illegal, it is not advisable to have tyres with a lower speed rating or load index than the manufacturer recommended tyre specification for your vehicle, or to have a combination of different tyre construction types. Consult your vehicle handbook to confirm your vehicles tyre speed rating and load index as well as any additional requirements.
