255/70R22.5 Tire Specs Explained | Load Range And Diameter

Reading 22.5 as tire height causes bad clearance math and cramped dual spacing — that digit is the wheel diameter. Each value in the 255/70R22.5 specs answers a separate question: tread width, sidewall height, casing build, and legal load.

What Does The 255/70R22.5 Marking Actually Mean?

Each block describes geometry, not capacity: 255 sets nominal width, 70 sets sidewall height as a percentage of width, R means radial, and 22.5 is the wheel diameter.

• 255 — 255 mm nominal section width, about 10 inches. Measured width runs from roughly 9.65 inches (Sailun S637) to 10.8 inches (Continental HSR2 SA), depending on model and approved rim.
• 70 — sidewall height near 70% of 255 mm, or 178.5 mm (about 7.03 inches per sidewall).
• R — radial casing, body cords at 90 degrees to the centerline.
• 22.5 — wheel diameter in inches, never overall tire height. Add two sidewalls to the wheel and you land near 36.5 inches.

Nominal is the operative word. Published overall diameters span 36.0 to 37.2 inches, so the stamp alone won’t tell you whether a tire clears a tight wheel well. The size shows up on steer, drive, trailer, urban delivery, long-haul, and RV service. A 70-series sidewall on a 22.5-inch wheel gives less cushion than a 75- or 80-series — the trade for a shorter tire and tighter wheel-well fit.

Load Range H, Load Index, And Speed Symbol

Most current 255/70R22.5 listings carry Load Range H, a 16-ply rating, but the load index sets actual capacity: 140 single, 137 dual on the common 140/137 version.

Load Range H is a capacity class, not a claim that the casing physically holds 16 plies. Fitting a dual assembly with the single-tire figure overloads both tires — how sidewall failures start.

The trailing letter is the speed symbol, capping highway speed: L at 75 mph, M at 81 mph, K at 68 mph. A 140L and 140M share load but not speed, and the complete marking — say 140/137M — governs both. Axle ratings, vehicle limits, and regulations can sit lower than the tire’s own figure.

Two H-rated tires can still differ on the lot: a retreaded or used casing carries the same size stamp as a new tire, and a 140K version won’t match a 140M’s highway speed. SimpleTire’s commercial 255/70R22.5 listings show how much the second half of the marking varies by model, even within a single brand.

255/70R22.5 Tire Diameter And Width: Why The Numbers Move

Two tires stamped 255/70R22.5 can stand more than an inch apart in height, because tread design, casing construction, and approved rim width shift the finished dimension.

That 1.2-inch spread is a 3.3% circumference difference — enough to pull a speedometer and odometer off by roughly the same margin. Approved rims cluster between 7.50 and 8.50 inches, and the published 120 psi figure is a maximum cold pressure, not a daily setting.

On a dual assembly, paired tires need the vehicle maker’s specified spacing so sidewalls never touch under load; fitting a 10.8-inch section where a 10.0-inch belonged can close that gap.

Our tested 255/70R22.5 tire roundup sorts models by actual service duty.

Before mounting, confirm rim width, axle rating, dual spacing, clearance, cold inflation from the placard, and tread position. A size match only proves the stamp agrees; a qualified commercial tire professional should verify the rest and mount it.