255/40 R20 Tyres Explained

255/40 R20 is a popular tyre size for cars that need 20 inch wheels with low profile handling. The numbers explain the tyre dimensions. 255 is the tread width in millimetres. 40 is the aspect ratio, so the sidewall height is 40% of 255mm (about 102mm). R20 means a radial tyre that fits a 20 inch rim. This size is chosen where sharper steering and high speed stability are important. You'll find both high performance summer tyres and all season or SUV options in this size. Premium brands on the page include Michelin, Continental, Pirelli, Bridgestone and Goodyear. mid range manufacturers listed include Hankook, Kumho, Yokohama and Falken. Value options include Accelera, Pace, Nankang and Westlake. For example, you can buy 255/40 R20 from Michelin (Pilot Sport 5) or Continental (SportContact 5P). To confirm fit, check your current tyre sidewall, the driver's door sticker or the vehicle handbook, or enter your registration for exact matches.

The first 3 sets of numbers that you will see when reading a tyre size tell you the width, profile and diameter of your tyre. In this case, for the tyre size 255/40 R20 this is broken down as follows: 255 - the width of the tyre in millimetres. In this case 255mm wide. 40 - the height of the sidewall as a percentage of the width. In this case 40% R20 - the diameter of the tyre's inner rim in inches. Essentially what size of wheel this is intended to be fitted onto. For this size, that is a 20 inch wheel

There is no standard recommended tyre pressure for 255/40 R20 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 255/40 R20 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 255/40 R20 can be worked out by using the tyre's profile size. For the tyre size, the profile is 40. What this tells us is that the sidewall height is 40% 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 40% of 255 – which is 102mm.