How to read a truck tire size
315/80R22.5 156/150L, 12R22.5, 385/65R22.5 160K… what the markings on a truck tire sidewall mean.
Metric size: 315/80R22.5
- 315 – section width in mm.
- 80 – aspect ratio: sidewall height as % of width. 80% of 315 ≈ 252 mm sidewall.
- R – radial construction (almost all truck tires are radial).
- 22.5 – rim diameter in inches. 22.5, 19.5 and 17.5 are the common truck rims.
Load and speed index: 156/150L
The first number (156) is the load a tire can carry fitted single; the second (150) is the load per tire fitted as a dual. 156 = 4,000 kg, 150 = 3,350 kg. The letter is the speed symbol: K = 110 km/h, L = 120 km/h, M = 130 km/h, J = 100 km/h.
Old inch sizes: 12R22.5, 13R22.5, 12.00R20
Here the first number is the width in inches and the aspect ratio is not written. 12R22.5 has about the same outside diameter as 295/80R22.5, and 11R22.5 as 275/80R22.5. Sizes such as 12.00R20 are older tube-type sizes used on split rims. See the inch ↔ metric equivalents table.
Wide singles (super single): 385/65R22.5, 385/55R22.5
Wide single tires used on trailers and on the steer axle of some tractor units. 385/65R22.5 is common on trailers and tippers, 385/55R22.5 on lower (mega) trailers.
Other sidewall markings
- M+S / 3PMSF (mountain snowflake) – mud and snow capability.
- REGROOVABLE – the tread can be regrooved.
- DOT 2324 – production date: week 23 of 2024.
- Steer / Drive / Trailer – which axle the tire is designed for.
If unsure, take a photo of the sidewall of your current tire.