Skip to content
TreadMathSupport Us
Size comparisons

265/60R20 vs 35x12.50R20 — the biggest thing on a factory 20

A third-generation Tundra's factory tire against the largest flotation size commonly stocked for the same wheel.

265/60R2032.52 in tall10.43 in wide35x12.50R2035.00 in tall12.50 in wide+2.48 in · +7.63%
Drawn to scale from the size codes. Solid outline is 265/60R20; dashed outline is 35x12.50R20. The bars below each tire are section width at the same scale.

35x12.50R20 is 2.48 in taller than 265/60R20 (7.63%) and 2.07 in wider. A speedometer calibrated for 265/60R20 would under-read by 7.63%.

Measured against each other

  • Overall diameter

    32.52 in35.00 in+2.48 in (+7.63%)

  • Section width

    10.43 in / 265 mm12.50 in / 318 mm+2.07 in (+19.81%)

  • Sidewall height

    6.26 in7.50 in+1.24 in

  • Circumference

    102.2 in110.0 in+7.8 in

  • Revolutions per mile

    620.2576.2-43.9

  • Ride height at the axle

    ——+1.24 in

  • Speedometer reading

    ——+7.63% under-read

Calibrated for 265/60R20, running 35x12.50R20

Dial reads 30
32.3 mph
Dial reads 50
53.8 mph
Dial reads 70
75.3 mph
Odometer counts 100
107.6 mi covered

Change either size in the comparison tool, or see the full speed table in the speedometer error calculator.

35x12.50R20 is effectively the ceiling of the 20-inch flotation range in general circulation. Everything above it exists but is rare, expensive and mostly aimed at heavy-duty trucks.

The step to the ceiling

2.48 in of diameter, 7.63%. Section width up 2.07 in, or 19.81%. Sidewall from 6.26 in to 7.50 in.

That last line is the one worth pausing on. Both of these are short-sidewall tires by any absolute standard — a 35 on a 20-inch wheel has less rubber between rim and road than a 31-inch tire on a 15-inch wheel would. The wheel diameter, not the tire's nominal size, sets that.

Why nobody re-gears this one

Starting at 3.73:1, the conversion returns 4.01:1; the closest set sold is 4.10:1, which overshoots. Owners of this platform carry the error instead, and a transmission with a large number of closely stacked ratios hides more of it than an older, wider-stepped one would.

What is carried is 7.63%: a dial reading of 80 against a road speed of 86.1.

The derived aspect ratios coincide

An unusual detail: both sizes work out to a 60-series. 265/60R20 states it; 35x12.50R20 arrives there by having 7.50 in of sidewall on a 12.50 in casing. So these two tires are the same shape at different scales, which is why the flotation size looks like a natural enlargement of the factory one rather than a different sort of tire.

Where the width goes

Two inches of extra casing on a full-size truck's factory 20-inch wheel is the constraint most likely to bind, and the factory wheel's width and offset were not chosen with a 12.50 section in mind. That is measured on the vehicle with the wheels turned.

Load rating is the separate question

A 35x12.50R20 sold for a full-size truck is normally an LT construction: a heavier casing, a much higher reference inflation pressure, and a load index calculated on the light-truck scale. 265/60R20 as an original fitment is frequently not. Two tires of similar rated capacity can arrive there by different routes, and the placard inside the driver's door states what the vehicle requires regardless of which route the tire took.

The metric alternative on the same wheel

If the flotation size is more than the truck can take, 285/65R20 reaches 34.59 in — within half an inch of a 35 — on a casing 1.28 in narrower.

Related