How to read a truck tyre sidewall

A truck tyre sidewall tells you four things in this order: what size it is, how much load and speed it is approved for, which standards it was built and approved to, and the week it was made. These markings provide a useful starting point for checking the specification.

Below is every marking on a modern 22.5in truck tyre, in the order the moulding puts them.

On a modern truck tyre the size reads 315/80R22.5. Four pieces of specification information, and only one of them is in inches.

315 is the nominal section width in millimetres, across the widest part of the sidewalls on the designated measuring rim. It is not the tread width, and not what you will measure on a rim narrower or wider than that.

80 is the aspect ratio: section height as a percentage of section width. Eighty per cent of 315 mm is about 252 mm of sidewall. Lower the ratio and you lower the vehicle and stiffen the sidewall, which is why 385/55R22.5 exists.

R is radial. A hyphen instead, as in 12.00-20, means crossply; B means bias-belted, now rare in truck sizes.

22.5 is the nominal rim diameter in inches. Half-inch sizes — 17.5, 19.5, 22.5 — use a 15 degree drop-centre tubeless rim; whole-inch sizes such as 20 are usually the older tube-type family.

Export and older sizes such as 11R22.5 and 12.00R20 declare no aspect ratio and give a nominal width in inches instead.

Those four elements also give you overall diameter without a tape measure: rim diameter in millimetres plus two section heights. For 315/80R22.5 that is 571.5 + 504, about 1,075 mm — the starting point for every rolling circumference question.

Immediately after the size comes the service description — 156/150L. Two load indices and a speed symbol.

The first index applies in single fitment, the second in dual. The dual figure is always lower, because two tyres side by side never share load perfectly. On a twin fitment, the second number is the one that counts.

The letter is the speed symbol: the maximum speed at which the tyre may carry its rated load. L is 120 km/h, K is 110, J is 100. Truck tyres often carry a second service description in brackets, such as 156/150L (154/150M) — a lower load at a higher speed. Both are valid. Full detail in load index and speed symbol explained.

TUBELESS or TL means the tyre has a butyl inner liner and a bead designed to seal against the rim flange and seat. TUBE TYPE or TT means it needs an inner tube and, in most sizes, a flap.

Practically all 17.5, 19.5 and 22.5in fitments are tubeless. Tube-type survives in 20in truck sizes, in agricultural and earthmover fitments, and in export markets with older wheel stock. Never fit a tubeless tyre to a rim designed for a tube and no flap.

M+S is essentially a manufacturer’s declaration that the tread geometry is intended for mud and snow. No compulsory performance test sits behind it, so condition and suitability for the operating conditions must also be checked.

The three-peak mountain snowflake, 3PMSF, is different: it is only permitted where the tyre has passed a defined snow traction test against a reference tyre, providing a tested performance marking. Winter obligations vary between European countries and change from year to year — check the requirement for the countries a vehicle actually runs in rather than relying on a marking alone.

A capital E in a circle, followed by a number and a longer approval number, is a UNECE type approval. The number in the circle identifies the country whose authority granted it, not where the tyre was made: E1 Germany, E2 France, E3 Italy, E4 Netherlands, E11 United Kingdom. A lower-case e in a rectangle is the parallel European Union approval.

Commercial tyres are approved under the UNECE regulation for tyres for commercial vehicles and their trailers, and separately for rolling noise, rolling resistance and wet grip — hence two E-marks on many sidewalls. An unmarked or wrongly marked tyre is not saleable for UK road use, whatever the casing is like.

The DOT code is a United States requirement, but it appears on nearly every tyre built for a global market: DOT, then a plant code, a size code, an optional manufacturer’s code, then four digits.

Those four digits are all most people need: the first two are the week, the last two the year, so 2224 is the twenty-second week of 2024. Three-digit codes are pre-2000 and should not be in service. The full code is normally on one sidewall only, so a tyre fitted the other way round on a twin can hide its own date.

Age limits now apply to tyres on the steered axles of heavy goods vehicles, buses and coaches, and to minibuses, and the DOT code is the only evidence of age a tyre carries. Confirm the current wording with DVSA before writing it into a workshop procedure; the principle is that the date code is an inspection item on every front-axle commercial tyre.

A retreaded commercial tyre must be identifiable as a retread. Expect the retreader’s name or mark, the size and service description as retreaded, an approval mark for the retreading process, and a date for when it was retreaded.

The trap is the original casing’s DOT code. On a pre-cure retread the original sidewall survives, so the original date may still be legible beside the retread date. Casing age governs whether the tyre should be in service at all; the retread date governs how much of its second life is left. More in retread or replace.

REGROOVABLE moulded into the sidewall means the tyre was designed with a defined depth of rubber beneath the groove base, so the pattern can be recut once the original tread is worn down.

Regrooving is lawful only on tyres marked for it, only to the manufacturer’s own template and depth, and only with a proper regrooving iron. Cutting into the belt package damages the casing. Never regroove an unmarked tyre.

Low on the sidewall you will find something like TREAD 4 PLIES: 2 STEEL + 2 NYLON — SIDEWALL 1 PLY STEEL. A construction declaration, and a useful one: it tells you whether this is an all-steel casing or a steel-belted casing with textile body plies. All-steel casings are the ones worth managing as assets, because they are the ones a retreader will take.

Where you see a ply rating such as 16PR or a load range letter instead of a load index — normal in agricultural, industrial and earthmover sizes — read ply rating and load range, for an explanation of the strength rating.

One thing you will not find on the sidewall is the tyre label. Its parameters are rolling resistance (fuel efficiency), wet grip, and external rolling noise in decibels with a class, plus snow and ice pictograms where the tyre qualifies. They are declared per pattern and size and carried on documentation and in the product database, not moulded into the rubber.

Truck tyres, class C3, are inside the scheme, so the label data has to travel with the tyre to the end customer. Great Britain and Northern Ireland arrangements have diverged since 2021 — if you import, confirm which applies to your stock.

Finally, the maximum load and the pressure it applies at: MAX LOAD SINGLE 4000 kg AT 900 kPa COLD, usually repeated for dual fitment and in pounds and psi. Nine hundred kilopascals is 9 bar, about 130 psi.

Read it as a pair, never as two facts. The load is only available at that pressure. Run the same tyre at 7 bar and its capacity is lower — the load and pressure table tells you by how much, the sidewall does not. Set pressure from the actual axle load and check it cold.