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How to find your tyre size?

Before changing your tyres, the first thing you’ll need to know is what tyre size your car uses. Do note that continental vehicles like Mercedes or BMW sometimes have staggered fitted wheels, which means different tyre sizes for the front and rear wheels so you'll also need to check both front and rear wheels just to be sure that you’re finding the right tyre sizes.

Where to find your tyre size?

The easiest way to find your tyre size is to look at the sidewall of the tyres that is currently fitted on your car. The tyre size shown above reads 245/45 R18

Other ways to find your tyre size:

Look behind the fuel flap cover or the sticker label at the driver’s door jam panel. You can also refer to your vehicle handbook for tyre size references.

How to read your tyre size?

The tyre size is broken down into its width, profile, diameter, speed rating and load index.

This tyre size reads 245/45 R 18 Y XL

Tyre Width - '245'

The first 3 digits of the tyre size indicates the width of the tyre. This means a ‘245’ tyre width will measure 245mm from one end of the sidewall to the other.

Tyre Profile - '45'

The tyre profile gives you the height of your tyre. The 2 numbers after the slash(/) is the aspect ratio measurement in percentage of the tyre width. The aspect ratio of ‘45’ translates to a height of 45% of the 245mm tyre width. In other words, the lower the tyre profile, the narrower your sidewall will be, vice versa.

Rim Diameter - '18'

The last 2 numbers after the R tells you the size of your rims. For this tyre marked with ‘18’, it means that the rim or wheel size is 18 inch in diameter. Therefore, sizes with diameter ‘16’, ‘17’, ‘19’, ‘20’ will not be able to fit onto the same rims.

Speed Rating and Load Index - 100Y XL

The speed rating and load index are the last two measurements that you can look at. The speed rating and load index are shown after the tyre diameter, at the end of the tyre size.

In this case, for 245/45 R18 Y XL, the ‘Y’ refers to the speed rating. The higher the letter alphabetically, the higher the speed rating. Tyres are usually replaced with similar or higher speed rating to maintain the vehicle’s speed capability.

The load rating, usually in numbers, is shown in smaller font just below the tyre size reading. For this case, it is shown here as ‘100Y’, whereby ‘100’ is a code for the maximum weight the tyres can support and the ‘XL’ at the end refers to Extra Load for heavier vehicles like SUVs to cope with the weight and also the higher tyre pressure these vehicles need to run at.

In addition, for most continental cars, they usually do not come with spare tyres. Thus, these cars are normally fitted with runflat tyres labelled with RFT/Runflat on the sidewall. These tyres have reinforced sidewalls so in the event of a tyre puncture or flat tyre, you can still travel at a maximum speed of 80km/h to your nearest tyre workshop to have your tyre patched or replaced.

Lastly, it is important that when you replace your tyres or upsize/downsize your wheels, the tyres are fitted with the same size or converted up/down according to your vehicle’s specifications. This is because a different size(in terms of overall diameter) that deviates too far from your original size(overall diameter), would give your speedometer an inaccurate reading. In other words, if your tyre size is not replaced to the same size or converted up/down correctly, you might actually be speeding!

When in doubt, you can always just snap a photo of the whole tyre as shown above and send it to any tyre workshop to identify the size. Feel free to drop us a call or pm us with your car make/model and we would be able to find out the recommended tyre sizes for your vehicle. An easy way to enquire for size availability would be to read the numbers from left to right. For example, “Hi, do you have 225, 45, R18 tyres?”

If you are planning to replace your tyres or change your rims to a smaller or larger size, enjoy peace of mind when you change them with us as we will follow your previous or recommended measurement and fitment accordingly.


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Hock Seng Wah Tyres Trading

Tyres | Rims | Batteries

No 46 Yio Chu Kang Road S545558

6456 5858 | 9636 8289

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