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Tire sizes

275/65R20 — the rung the flotation ladder skips

Flotation notation on a 20-inch wheel goes 33, 35, 37. This is the size in the gap.

Metric notation · Light truck (LT-metric)

Overall diameter
34.07 in
865 mm
Section width
10.83 in
275 mm
Sidewall height
7.04 in
179 mm
Aspect ratio
65%
sidewall as a share of width
Wheel diameter
20 in
the hole in the middle
Circumference
107.0 in
2719 mm
Revolutions per mile
591.9
geometric, not measured
Revolutions per km
367.8
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

  • 35x12.50R2035.00 in tall+0.93 in
  • 33x12.50R2033.00 in tall-1.07 in
  • 37x12.50R2037.00 in tall+2.93 in

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

Platforms recorded with this size

The fourth-generation Chevrolet Silverado 2500HD is recorded here with 275/65R20 as factory equipment. That matters for reading the rest of this page: it is a heavy-duty original fitment rather than an aftermarket step, which is unusual for a size this close to a 34.

Between the two rungs everybody names

Size Diameter Against 275/65R20 Section width
33x12.50R20 33.00 in −1.07 in (3.15%) 12.50 in
275/65R20 34.07 in — 10.83 in
35x12.50R20 35.00 in +0.93 in (2.72%) 12.50 in

Flotation sizes on this wheel step in whole inches, so the 34-inch position simply does not exist in that notation. This code occupies it, and it does so on a casing 1.67 in narrower than either neighbour.

The distances are close to symmetric — 3.15% down to the 33, 2.72% up to the 35 — so a truck moving in either direction sees an indicated 70 mph land between 67.8 and 71.9 mph.

Its metric neighbours are much closer than its flotation ones

Where the flotation ladder is coarse, the metric one around this size is fine:

  • 285/60R20 — 33.46 in, 0.61 in shorter, 0.39 in wider
  • 285/65R20 — 34.59 in, 0.51 in taller, 0.39 in wider
  • 295/65R20 — 35.10 in, 1.02 in taller, 0.79 in wider
  • 275/60R20 — 32.99 in, 1.08 in shorter, identical width

Four codes inside two and a bit inches, each reachable by moving one of the three numbers. That is the practical argument for metric notation on a working truck: the increments are small enough to choose between.

A 34 on a 17-inch wheel, for comparison

34x10.50R17 stands 34.00 in — seven hundredths of an inch under this size — on 8.50 in of sidewall against this size's 7.04 in, and 0.33 in less section width.

The two are as close in rolling diameter as any cross-notation pair in the catalogue, and they are built for entirely different vehicles: one for a three-quarter-ton pickup on a factory 20-inch wheel, the other for an off-road platform on the smallest wheel that will clear its brakes. How the two notations are constructed, and where the correspondence stops, is set out in the metric versus imperial reference.

Related

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