A Tyre Marking Guide - Understand Your Rubber Better

Updated: Thursday, June 29, 2023, 18:33 [IST]

What are tyre markings? If we look at tyres closely, letters and numbers are visible - similar to a Mathematics formula, but surprise surprise, it's not really that! So, what do these sets of letters and numbers mean? Go no further, we have the answer right here.

On a tyre, if you've seen something similar to 'P150/60-R17 66W' or at least numbers and letters in the same format, that is what a tyre marking, or rather, the size marking is. But, what do these mean individually? In simple terms, it's the tyre usage, width, aspect ratio, tyre construct, height, load index, and speed rating.

Let's start off with the 'P' tyre marking. The letter 'P' is there not just for show, but because the tyre is used for a passenger vehicle. The 'P' simply stands for Passenger vehicle, whereas if 'LT' is seen, it would mean Light Truck.

After 'P', we have '150'. Here, '150' is the width from one sidewall to the other sidewall. The width is measured in millimetres, so in this case, the width of the tyre is 150mm. Next, we have '60'. This tyre marking is basically the aspect ratio of the tyre. It calculates the percentage of the height of the sidewall in relation to the width of the tyre. The higher the sidewall the more comfortable the ride is, but handling decreases (handling reduces with higher sidewalls).

'R' tells us that the tyre is a Radial Tyre. The letter in this place stands for tyre construction. Instead of 'R' we could also find 'B' which stands for Bias. Radial tyres are more often than not used in modern cars whereas Bias tyres are used in older models and those vehicles that are used rough, on tough terrains.

The tyre marking that follows the tyre construction code is the wheel diameter. In this case, the wheel diameter is 17 inches. It signifies the rim size that this tyre will fit on.

The final number seen on the tyre represents the load index of the tyre. The load index varies from company to company, with no constant load index being followed. Here, the load index is '66', and to find out how much weight it can hold, we'll have to contact the tyre manufacturer.

The 'W' tyre marking is the speed rating for the tyre. Not all tyres can be used when travelling at high speeds due to many variables, some being the quality of rubber, how hot the tyre gets, and the thickness of the tyre. Here, the 'W' rated tyres can travel up to 270km/h (168mph).

Now, moving to those codes that aren't involved with the tyre size: First, we have the temperature codes. These codes will either be an 'A', 'B', or 'C'. 'A' rated tyres can easily travel to speeds above 185km/h; 'B' rated tyres can travel from 160km/h to 185km/h; and, 'C' rated tyres can travel from 136km/h to 160km/h.

Finally, we may find arrow markings on the tyre. No, this isn't pointing to anything, instead, it shows which direction the tyre has to move. We only find arrow markings on unidirectional tyres as the grooves and treads are designed to work best when moving the correct way.

Thoughts On Tyre Markings

Tyre markings, although may be hard to wrap your head around, aren't there to confuse us or just for the sake of it. These markings actually give us a whole lot of information and shouldn't be looked past. Take some time off your day, go check your tyre out and try and see if you can figure it out yourself!