How to Read a Tire Sidewall: Size, Load Index and Speed Rating

Every specification we quote comes off the sidewall of the tire. If you can read that line of code, you can check a quotation before the container leaves.

Take 315/80R22.5 156/150 L as an example.

315 is the nominal section width in millimetres, measured across the widest part of the inflated tire. 80 is the aspect ratio: the sidewall height is 80% of the section width, so this tire stands about 252 mm tall from bead to tread. R means radial construction. 22.5 is the rim diameter in inches.

The next pair of numbers is the load index, and on a truck tire there are two of them because the tire can run single or in dual fitment. 156 applies to single fitment and 150 to dual. Converted to kilograms, that is 4,000 kg per tire single and 3,350 kg per tire dual. A drive axle running four tires in dual fitment therefore carries 13,400 kg on that axle, not 16,000 kg — a difference worth checking before you load a trailer to the plate.

The letter at the end is the speed rating. L is 120 km/h, which suits long-haul highway work. K is 110 km/h and is common on heavy-load patterns. On passenger tires you will see H (210 km/h), V (240 km/h) and W (270 km/h).

Two more markings matter for import. The DOT code, required for the United States, ends in four digits: the week and the year of production, so 3825 means the 38th week of 2025. The ECE marking, used in Europe, carries an approval number issued to the factory. Neither marking can be added after the tire is built, which is why buyers ask for them in writing before ordering.

Each pattern on this site carries a specification table with the same columns we read off the sidewall. Compare those columns against your inquiry list before you send it, and most of the back-and-forth disappears.