Tyre size checker

By David Sholicar

Tyres come in many different sizes to suit different vehicle models, so when the time comes to purchase new tyres, it is important to understand that one size does not fit all. Whether you want to learn how to determine which size tyres you need or if you're looking for more information regarding what tyre size numbers mean, you're in the right place.

Tyre Size

How to check tyre size?

Your vehicle's tyre size will be displayed in the handbook, or on a sticker located within the fuel cap door or driver's door jam. Additionally, all tyres have sizing information printed on their sidewall, which makes it easy to double check which size tyres are suited to your vehicle even if you don't have any paperwork to hand or the stickers have become unreadable for any reason. 

When looking at the sidewall of your tyre, you will see a printed set of numbers which, when read from left to right, denote your tyre size. The formation of these numbers will look something like 205 / 50 R16 91 V. But what exactly do these numbers mean? 

Understanding your tyre size

When speaking with a qualified technician, providing this set of numbers will instantly tell them all they need to know to provide you with accurate advice with regard to the best tyre options for your vehicle, budget, and driving style. 

However, it is always beneficial to have a good understanding of your own vehicle, so let's explore our tyre size guide, which sets out precisely what each of the numbers refers to. 

- Width 

The first three digit number relates to the width of your tyres in millimetres. The higher the number, the wider the tyre. Wider tyres are known for offering enhanced grip, however, this can result in additional road noise. 

- Profile 

Also known as the aspect ratio, the second number in the sequence refers to the height of the sidewall divided by the tyre's width, multiplied by 100. So, if the number on your tyre is 50, the profile of your tyre is half or 50% of its total width. 

- Rim 

When a tyre is removed from a wheel, the part that is left is called the rim. As the rim width and the tyre width on your vehicle can be different, both measurements are clearly stated to avoid confusion or a poor fit. If the third number on your tyre is R16, your tyre's rim width is 16 inches. 

- Load index 

This number relates directly to the maximum weight that can be safely carried by the tyre at the tyre's speed rating. If your tyre has a load index of 91 and a speed rating of 148 mph, it can carry a total weight of up to 615kg. 

- Speed rating 

The last part of a tyre size number is actually a letter, which relates to the top speed at which the tyre is able to safely support the maximum load. So, if your tyre displays the letter V, you will know that this tyre can safely carry the maximum load at a top speed of 148 mph. 

- Extra numbers or symbols 

Some tyres will also display additional information. For example, some vehicles need tyres that have the ability to safely support a heavy load, which requires a higher than average inflation pressure. If your vehicle needs this type of tyre, you should look out for the initials RF (reinforced) or XL (extra load). 

Certain tyre brands, such as Bridgestone, utilise Runflat technology, which essentially provides additional support for the sidewalls. In practice, this technology enables drivers to continue to drive at 50 mph for up to 50 miles on a flat tyre. You may already be familiar with this technology if you drive a Mini or a BMW, as this type of tyre is most commonly used on these car models. 


It is vitally important to ensure that your vehicle is fitted with the correct tyres to ensure both optimal levels of safety and performance. If you are at all unsure about the size of tyres that your vehicle requires, it will be beneficial to contact a tyre expert for help and guidance. 

Your tyre size can be found in your vehicle's handbook and printed on a sticker positioned within the fuel cap door or driver's door jam. Additionally, all tyres have sizing information printed on the sidewall. 

Yes, simply enter your car reg on the link below and find out various options for your car

Find tyres using your Car reg.

Your car tyres have been selected due to their ability to fit correctly on your vehicle's rims. The combination of your rims and your tyres have also been balanced to aid optimal suspension and steering, thereby offering a safe and comfortable driving experience. 

If you were to change the size of your vehicle's rims, it would theoretically be possible to change your tyre size, however, the wheel's overall diameter would need to remain the same. If you did decide to change the diameter, there are other considerations that you would also need to make, including recalibrating your speedometer and adjusting your tyre pressure. 

It is important to never drive on mismatched tyres. Different tyres are designed with different tread patterns, which channel debris and water away from the surface of the tyre. This process allows the tyre to maintain a grip on the road surface, which is essential to safety, handling and performance. If you drive on mismatched tyres that channel debris and water in different directions, the handling of your vehicle on loose road surfaces or in wet conditions will be negatively impacted. Additionally, your vehicle's suspension will be put under unnecessary stress, which can cause premature and/or uneven wear. 

If you are ready to invest in new tyres for your vehicle, our tyre professionals are on hand to help and advise. Whether you're looking for support with selecting the correct size or you want to explore your options with regard to special design or performance features, we can help. Simply contact your nearest Protyre garage or use our online booking form to arrange an appointment with a qualified and knowledgeable tyre professional who can help you optimise your driving experience. 


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About the author

Article Author Photo
By David Sholicar
David is the National Retail Operations Manager for Protyre. One of David’s areas of responsibility and expertise is dealing with the DVSA and MOT’s for Protyre. As the Authorised Examiner Designate Manager ( AEDM ) David deals with applications for changes to the many Vehicle Testing Stations ( VTS’s) including managing the growth of the Number of MOT testing stations that Protyre operate, allocating MOT tester roles, and monitoring the MOT Test logs to ensure that Protyre MOT standards are maintained as the best in the industry.
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