255/55 R18 Tyres Explained

255/55 R18 is a common tyre size for SUVs, crossovers and larger family cars. The numbers are simple. 255 is the tyre width in millimetres. 55 is the aspect ratio, so the sidewall height is 55% of 255mm (about 140mm). R18 means the tyre fits an 18 inch wheel. You'll see this size on vehicles that need higher load ratings and good straight line stability. It's available from premium manufacturers such as Michelin, Continental, Pirelli, Bridgestone and Goodyear. mid range options include Hankook, Kumho and Toyo. Value choices on the page include Tomket, Leao and Nankang. Popular examples in 255/55 R18 include the Michelin CrossClimate 3 and the Goodyear Eagle F1 Asymmetric 6. To confirm this is the right size for your car, check the tyre sidewall, the driver's door sticker or your vehicle handbook. You can also enter your registration for exact matches, and make sure the load and speed ratings (or XL if required) match the manufacturer's recommendations.

The tyre size that you find on the sidewall of a tyre will tell you important information such as the width, profile and diameter of your tyre. In this case, for the tyre size 255/55 R18, this means the following: 255 - the width of the tyre in millimetres. I.e. 255mm wide. 55 - the height of the sidewall as a percentage of the width. In this case 55% R18 - the diameter of the tyre's inner rim in inches. Basically what size of wheel this is designed to fit onto. In this instance it is a 18 inch wheel.

There is no standard recommended tyre pressure for 255/55 R18 tyres, as each vehicle manufacturer will recommend their own optimal tyre pressure so you can enjoy the best performance from your vehicle. If you are unsure as to the correct tyre pressure for your 255/55 R18 tyres, there are a few different places you can look to find this information. Vehicle handbook - There is a section in most manufacturer handbooks which covers all the technical details for a tyre. This includes the tyre size, load rating, speed rating and tyre pressure. Tyre label - The tyre label is often found on the door jamb of the driver’s side. It is a small rectangular sticker which contains the information you need to know in regards to tyre pressure and tyre sizes. It should also tell you the tyre pressure recommendation

The height of your tyre's sidewall for the tyre size 255/55 R18 can be worked out by using the tyre's profile size. For the tyre size, the profile is 55. What this tells us is that the sidewall height is 55% of the cross-section width of the tyre. The sidewall height is determined by the distance between the rim line and the tread line. So, as this tyre has a cross-section width of 255mm, the height of the sidewall is 55% of 255 – which is 140.25mm.