The meaning of tyre markings
Radial, aspect ratio, load index, run flat, TWI… …so many codes on the sidewalls of tyres, but what do they all mean?
For most of us who get a professional to change our tyres, we may never need to know. But just in case you ever want to source your own tyres, or even if you’re just curious, here’s a quick guide to the meaning of tyre markings.
The tyre size is indicated by a combination of numbers and letters that should look something like this: 195/60 R15 88 H. Each of the numbers and letters in this example refer to the following, but vary from tyre to tyre.
195 = the section width in mm. So this would be 195mm across the tread from sidewall to sidewall.
60 = the aspect ratio, or the profile height of the sidewall as a percentage of the tyre width. In this example, the tyre profile height is 60% of the tyre width.
R = Radial tyre, which counts for most tyres manufactured these days.
15 = the size of the wheel rim in inches.
The letter refers to the maximum speed at which the tyre can travel. In this case, H means that the tyre can travel at 210kph (130mph). See the table below for the full scale.
91 = the tyre’s load capacity. This number is not the weight itself, but represents a point on a scale (615kg in this case). See the table below for the Load Index scale.
DOT serial number
This is a combination of numbers and letters (e.g. DOT P2XL BCSC 2915) that, first of all, refers to the fact that the tyre meets or exceeds the Department of Transport safety standards (DOT). The following serial number that helps the manufacturer identify the tyre and production facility, and the final four numbers refer to the date on which the tyre was made. This is particularly important when buying second-hand tyres. In this example the tyre would have been produced in the 29th week of 2015.
Some tyres have a higher load index and are often marked with a corresponding symbol, as follows:
Run Flat Tyres
Run-flat tyres are designed to withstand the pressure of a flat tyre so you can travel a short distance to have the tyre repaired. The code will depend on the manufacturer (ROF, SSR, ZP etc.). Find out more about Membat’s Passion RFT.
Tread Wear Indicator (TWI)
Treat Wear Indicators are raised bumps within the largest treads, distributed evenly around the circumference of the tyre. You can use these indicators to gauge how much wear your tyres have left.
If you’re unsure about any of the markings on your tyres, or about how to select and replace your tyres, always refer to the vehicle manufacturer’s handbook and contact a professional tyre-fitting service.
Speed rating table
|Speed Rating||Speed (mph)||Speed (km/h)|
Load Index Table
|Load Index||Weight (kg)||Load Index||Weight (kg)||Load Index||Weight (kg)||Load Index||Weight (kg)|