Correct tire sizes & tire size conversion chart explained!


Posted by: Oluwaseun Solomon

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Does it confuse you when mechanics and auto experts talk about tire sizes and tire size conversion stuff? Read this short article now and you'll get it all!

When it comes to general car maintenance, regular tire maintenance is very important and when tires are worn out, it is best to replace them. Yes, even that vintage lovely car from your collection may really require a tire replacement to be on the safer side. In any case, a reliable tire size conversion chart will really help you in comparing tire sizes as well as in finding the right measurement of tires.

However, realizes that automobile newbies will get confused trying to read a tire size conversion chart. This is why we will provide a brief guide on how to understand and easily read a tire size comparison chart below:

1. Tire size conversion chart – What is it?

It’s actually simpler than you might think. Whether you are looking for the right replacement tires for your vintage car’s old ones or you are just looking to buy a new tire generally. The tire size conversion chart simply helps you to figure out the correct and right measurement. You should not always expect the tire size conversion chart to just give you perfect measurements, it will just help in narrowing down the variables. A couple of other factors like the diameter and wheel size are the major determinant of correct tire sizes.

When comparing two tires, it might be best if you just compare the tread footprint and outside diameters to see how much they match. We also recommend you seek the advice of your local tire dealer when shopping for new tires.

You can refer to tire size conversion chart here.

2. How do you understand tire sizes?

Check your car’s manual first to confirm the size of your vehicle’s tire. After that, you can check a front tire’s sidewall to find a sort of number sequences like 225/50R-16 or 185/60R-14 and any similar sequence. Now let’s assume your car tire has a number sequence like; 225/50R-16, the first number “225” is describing the width of your tires in millimeters measurement, i.e. 225mm will be 8.9 inches approximately. So, the width of your tire is 8.9 inches roughly.

Image-showing-a- labeled -tire-sidewall

Tire size conversion chart is not so difficult to understand and it’s very important as well

The other part that reads “50R” is actually carrying information of 2 types. First is the numeric part that reads “50”, this means the sidewall height (aspect ratio) of such tire is 50% of that same tire’s width. What this means is 50% of 8.9 inches which equals 4.45 inches approximately. So, the height of your tire is 4.45 inches. Now, the second part of the “50R” which is the letter “R” is an indicator of such tire’s speed rating and in this case, the “R” means less than 150mph tire speed rating. Note that; tires which carry the letters “ZR” at this part are designed to run at speeds which are greater than 150mph.

The last part of that number sequence which reads “16” is simply indicating the compatible size of wheels that the tire can fit. This means that wheels that are 16-inch in diameter are the ones that are most compatible with such a tire.

Note: If your vehicle’s rear tires are somewhat different from the front ones, you can apply this same reading approach to determine the correct rear tires information.

>>> Detailed instructions to interpret tire markings: Tyre size guide: how to find tire markings & interpret them

How to Read Tire Sizes and Specifications?

3. Correct tire measurements – Are they important?

Well, correct tire measurements are very important because when you are replacing old tires, the new ones must just match the old ones you are removing. To ensure your safety and better driving performance of your vehicle, every single specification and dimension should be similar in both the old and new tires. These dimensions include; wheel diameter, tire height, speed rating, and tire width.

For instance, the speedometer accuracy will be much affected by a mismatched tire diameter in any vehicle. You will experience frequent bumps caused by your car’s chassis or body on the surface of the road. This will occur when you are driving with new tires that have height and width that is larger than the old ones or just larger than the specification in the car’s manual. Also, you can start having troubles with the vehicle’s ABS system caused by the wheel sensors being affected by incorrect tire sizes.

4. Conclusion

Naijauto advises that you take some time to figure out the correct tire sizes that match your old tires whenever you are shopping for tire replacement. Don’t just scan through the tire size conversion chart in a hurry and go place an order just like that. Take time to understand all we have explained above. Try to get the correct sizes of your old car tires applying the techniques we have discussed above, then proceed to place your order when you are sure of your readings.

>>> Check for more Naijauto posts on car maintenance and safe driving tips!

Oluwaseun Solomon

Oluwaseun Solomon

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Oluwaseun Solomon is a prolific and diligent automobile writer at He's also an experienced digital marketer and a creative multimedia developer that specializes in video editing. He currently contributes informative and easy to read articles on topics covering transportation, traffic updates, auto industry updates, and different car reviews.
When Solomon is not writing, you will either find him composing music, editing videos or simply enjoying YouTube "TEDx Talk" videos with a chilled drink :)

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