Cars just aren’t designed to accommodate such great changes, which is why rules such as the 1.5% or -2% are regularly used. Similarly, you couldn’t go up from a 185/80 R13 to a 225/40 R18 tyre due to a look of space in the wheel arch. You can’t replace a standard 225/40 R18 tyre, for instance, with a 185/80 R13 tyre, as the smaller model would require 13 inch wheels that can’t fit the braking discs from the larger 18 inch wheels. Likewise, you need to be careful when changing the diameter of the tyre. As such, always keep the physical needs and parameters of your vehicle in mind. Our tyre calculator does not, for instance, take into account your specific car or model. Our tyre diameter calculator is a great tool for finding a new tyre size, but you should keep in mind some physical limitations. An alternative sizes can offer various improvements, such as a shorter braking distance, as well as drawbacks, so it is important to understand what it is you want from your car tyres.įind the correct tyre sizes for your vehicle. For most drivers, this is done to achieve or improve certain driving parameters on their vehicle. When it comes to these results, it is recommended that you only use options within 1.5% and -2%. Our tool gives this in percentages: a positive number is larger/wider, while a minus number represents a negative change. When using a tyre size comparison tool, it’s important to know the difference in the outer diameter.
They are typically larger - upgrading in this way is referred to as plus sizing. Alternatives, on the other hand, have a different size.
When it comes to choosing a new size, many drivers choose to stay within the same size and diameter - these tyres are known as equivalents. We think it is better to know for sure that you are buying the correct size tyre.The tyre size calculator does not include information about car make and model. Please keep in mind your car's capabilities. Many such searches will still ask you to identify your tyre size from a number of options anyway.
While it is possible to use your car registration to find your tyre size, this is unreliable and could result in you spending a lot of money on the wrong size tyre. We think everyone should be able to find and understand their tyre size. WhatTyre wants to promote tyre knowledge in the wider car tyre market. Why can’t I just put my car reg number in? The load index of 91 means it can carry a load of 615kg. Therefore, our example tyre has a maximum speed of 150mph as it has the speed rating V. Most car tyres for road use have a maximum speed between 118mph (T) and 187mph (Y). This is the fourth and final part of your WhatTyre tyre search. This tells you the maximum speed the tyre is suitable for. The number is the “load index”, or how much weight the tyre can carry. These figures show the limits of how you can use the tyre. What do the numbers and letter after the tyre size mean?Ĭongratulations! You are officially interested in tyres. The letter R means “radial” which is the way the tyre is constructed. WhatTyre’s Search By Tyre Size function currently allows you to search for tyres with rim sizes from 13 to 24. It is expressed in inches and increases in increments of 1. This number also increases in increments of 5.ġ6 is the rim size, or the diameter of the inside of the tyre. So, the profile of our example tyre is 55% of 205mm, or 112.75mm. It is commonly known as the “aspect ratio”. The number is the percentage of the width of the tyre. WhatTyre’s Search By Tyre Size function allows you to select widths between 165 and 305.ĥ5 refers to the profile of the tyre, or the distance between the wheel and the edge of the tyre, looking at it from the side. Using our example size, 205/55 R16, this is what each number means:Ģ05 is the width of the tyre tread in millimetres. Another few characters follow the size, like 91V on our example tyre. It consists of three key numbers for example, 205/55 R16. Tyre sidewalls contain a lot of information, but the size is usually quite prominent, in some of the biggest writing. You will find your tyre size on the side of your current tyres.