What Do Numbers on Tyres Mean?

Have you ever seen those numbers on the side of the tyre and not known what they mean? Believe it or not, many people have no idea what these codes mean. It’s time you learn exactly what they mean.

Each tyre has a specific code on the side. An example would be 205/55R16 91W.

The way of understanding this series of numbers is slightly complicated because different units are used including an imperial measurement.

The first set of numbers, e.g. 205, is the width of the tyre measured in millimetres. This is measured across the tread from one sidewall to the other sidewall.

The second set of numbers after the forward slash, e.g. 55, is a percentage. This is the aspect ratio which indicates the percentage of the width. To simplify, this number would read as 55% of 205mm.

The letter R means radial construction. Not all tyres are made as radial construction models but a good majority is. Cross-ply tyres would be the opposite of radial construction. Cross-ply has fabric crossing over each other at the same angles.

The third set of numbers, e.g. 16 which is measured in inches, tells us the diameter of the inside of the tyre. Sound familiar? This is the diameter that your rims need to be in inches.

The fourth set of numbers, e.g. 91, is the load rating. The maximum weight each tyre will be able to handle using this digit is 615kg. The calculation is slightly complicated and luckily there are charts available to determine the weight your tyre can handle.

The last letter, e.g. W, indicates the speed rating. It tells you what speed the tyre will be able to handle. In this case, it can handle 168mi/h or 270km/h. Other numbers include letters A all the way to Z. Can you imagine how low A must be? An A would indicate that it can handle 5km/h.

So now you have important knowledge regarding tyre numbers. Do you understand how they work and why we have these numbers? Everything in this world has to have a serial number with the exact specifications so that people can fit the correct parts to their vehicles. It avoids any confusion. It is also important for mechanics to know this information when fitting wheels and tyres on your car. If you are not present then they can easily look at the side wall of the tyre. If you are unsure about certain numbers on your car parts it would be wise to confirm the details with a tyre supplier.