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Tire sizes

285/60R18 — a dead heat with a light-truck 17

Two codes, one inch of wheel between them, and no measurable difference in how far either rolls.

Metric notation · Light truck (LT-metric)

Overall diameter
31.46 in
799 mm
Section width
11.22 in
285 mm
Sidewall height
6.73 in
171 mm
Aspect ratio
60%
sidewall as a share of width
Wheel diameter
18 in
the hole in the middle
Circumference
98.8 in
2511 mm
Revolutions per mile
641.0
geometric, not measured
Revolutions per km
398.3
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

  • 33x12.50R1833.00 in tall+1.54 in
  • 35x12.50R1835.00 in tall+3.54 in
  • 37x12.50R1837.00 in tall+5.54 in

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

Platforms recorded with this size

The 200-Series Toyota Land Cruiser is the vehicle recorded here with 285/60R18 as factory equipment — a wide, comparatively short light-truck size on a wheel that most of its competitors were using for something narrower.

The tie

245/75R17 measures 31.47 in. This size measures 31.46 in. Carried to two decimal places the gap is 0.00 in — 0.01% — which is the closest agreement between any two codes in this catalogue that do not share a wheel diameter.

Everything else about them is different. This tire is 11.22 in wide with 6.73 in of casing above the rim; the 17-inch code is 9.65 in wide with 7.23 in. One is specified for a heavy full-size SUV on an 18-inch alloy, the other for pickups and utility vehicles that were still being delivered on 17s.

A vehicle moving between the two would see no change on the speedometer, no change on the odometer, no change in engine speed at a given road speed and no change in ride height. It would gain or lose 1.57 in of section width, which is the only thing actually happening.

Its own wheel, by height

Size Diameter Against 285/60R18 Section width
255/60R18 30.05 in −1.42 in 10.04 in
265/60R18 30.52 in −0.94 in 10.43 in
285/60R18 31.46 in 11.22 in
265/65R18 31.56 in +0.10 in 10.43 in
255/70R18 32.06 in +0.59 in 10.04 in
275/65R18 32.07 in +0.61 in 10.83 in

The fourth row is the useful one. 265/65R18 is a tenth of an inch taller on a casing 0.79 in narrower — near enough the same tire in every respect the arithmetic can reach, and visibly different on the vehicle.

Reaching upward from here

The next rung in the same width is 285/65R18 at 32.59 in: +1.12 in and 3.57%, an indicated 70 mph becoming an actual 72.5 mph. Above that, 33x12.50R18 stands 33.00 in, +1.54 in and 4.88%, and adds 1.28 in of section width along with the height.

The step to 285/65R18 is set out in detail in the comparison of the two.

Related

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