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Tire sizes

225/75R15 tire size — and the modern size that replaced it

The same 225 mm of tread, two inches more wheel, and almost exactly the same tire height thirty years apart.

Metric notation · Light truck (LT-metric)

Overall diameter
28.29 in
718 mm
Section width
8.86 in
225 mm
Sidewall height
6.64 in
169 mm
Aspect ratio
75%
sidewall as a share of width
Wheel diameter
15 in
the hole in the middle
Circumference
88.9 in
2257 mm
Revolutions per mile
713.0
geometric, not measured
Revolutions per km
443.0
geometric, not measured
Typical load index
108–129
2205–4079 lb per tire

LT-metric tires use a stiffer casing at a much higher reference inflation — Load Range C, D or E, meaning 50, 65 or 80 psi. The index band reflects the pressure the casing is rated to hold, not a larger tire.

The load-index range shown is the band this CLASS of size is typically produced in — not a list of what is in stock for this exact size today. Load index and speed symbol are printed on the sidewall of the specific tire you are holding, and the required minimum is on the placard of the specific vehicle you are fitting. Read both.

Nearest real sizes in imperial notation, same wheel

  • 30x9.50R1530.00 in tall+1.71 in
  • 31x10.50R1531.00 in tall+2.71 in
  • 32x11.50R1532.00 in tall+3.71 in

Compare any two sizes, including ones this site has no page for, in the comparison tool.

Platforms recorded with this size

28.29 in overall. 8.86 in of section width. 6.64 in of sidewall. 88.9 in of circumference and 713.0 revolutions per mile.

Compact pickups, small SUVs and full-size vans of the 1980s and 1990s used this size, and it remains in production largely for them and for the trailer market.

Thirty years, two inches of wheel, no change in height

225/65R17 measures 28.52 in. This size measures 28.29 in. The gap is 0.23 in, or 0.81%, and the section width is identical at 8.86 in.

What changed is the split between metal and rubber. The 15-inch version carries 6.64 in of sidewall; the 17-inch version carries 5.76 in. The vehicles that used one and the vehicles that use the other are separated by roughly two product generations, and the tire is the same height in both.

That is not a coincidence either. Rolling diameter is constrained by gearing, arch clearance and drivetrain calibration, none of which changed much. Wheel diameter was free to grow, so it did.

Stepping up on the same wheel

Fitted instead Diameter Difference Ride height change
215/75R15 27.70 in 0.59 in 0.30 in
235/75R15 28.88 in +0.59 in 0.30 in
30x9.50R15 30.00 in +1.71 in 0.86 in
31x10.50R15 31.00 in +2.71 in 1.36 in

Ride height moves by half of any diameter change, because the axle sits at the centre of the wheel and only the bottom half of the added rubber is between it and the ground. The metric ladder gives even 0.59 in steps; the flotation ladder above it jumps a full inch at a time.

Trailer service

ST225/75R15 is a widely stocked trailer size. The prefix marks a casing built to a trailer standard with a different construction and load rating at a higher reference inflation — same geometry, different product. The tire construction codes reference sets out the prefixes.

On the road-vehicle side, 15-inch light-truck wheels are no longer specified on new vehicles, so the demand for this size now comes almost entirely from replacement and from trailers. That keeps it in production but narrows the choice of tread patterns considerably.

Related

Class: Light truck (LT-metric). Every figure above is computed from the size code, not stored — see how these numbers are calculated.