235/45 R18 Tyres Explained

235/45 R18 is a popular tyre size for sportier family and mid sized cars that run 18 inch wheels. The numbers tell you the dimensions. 235 is the tyre width in millimetres. 45 is the aspect ratio, so the sidewall height is 45% of 235mm (about 105.8mm). R18 means the tyre fits an 18 inch rim. You'll find this size from premium manufacturers such as Michelin, Continental, Pirelli, Bridgestone and Goodyear. For example, Michelin's CrossClimate 2 and Continental's PremiumContact 6 are available in 235/45 R18. mid range options come from brands like Hankook and Kumho. Value choices on the page include Wanli and Tomket. 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 to check load and speed ratings.

The numbers 235/45 R18 are 3 very important pieces of information in regards to a tyre's size. They tell you the width, profile and diameter of a tyre. For a tyre that is 235/45 R18 this information can be broken down into the following: 235 - the width in millimetres of the tyre. In this case 235mm wide. 45 - the height of the sidewall as a percentage of the width. For this tyre that is 45% R18 - the diameter, in inches, of the tyre's inner rim. Letting you know what size of wheel this tyre should be fitted to. For this size, that is a 18 inch wheel

There is no standard recommended tyre pressure for 235/45 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 235/45 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 235/45 R18 can be worked out by using the tyre's profile size. For the tyre size, the profile is 45. What this tells us is that the sidewall height is 45% 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 235mm, the height of the sidewall is 45% of 235 – which is 105.75mm.