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255/30R20 in inches

A 255/30R20 tire is 26.0″ tall and 10.0″ wide, and fits a 20″ wheel. In inches it is written 26.0×10.0R20.

Diameter26.02″
Width10.04″
Sidewall3.01″
255/30R20 drawn to scale: 26.02 inch diameter, 3.01 inch sidewall, 20 inch wheel, 10.04 inch tread width20″ wheel3.01″26.02″ overall10.04″ wideSide view
Drawn to scale. Nominal dimensions calculated from the size code.
Manufacturer data

How tall 255/30R20 tires really are

Heights published by Michelin and Toyo for all 3 tires in this size. Their published revolutions per mile work out to 25.3″ under load (below).

Real 255/30R20 tires measure 26.10″, against 26.02″ from the size code. Every one runs taller than the size code.

Height under load25.3″

Published revs per mile (797–798) mean the tire rolls like a 25.3″ tire on the vehicle. Use this for speedometer calibration.

Weight spread23.3–25.1 lb

The lightest (Michelin Pilot Sport 4 S, XL) is 1.8 lb lighter per corner than the heaviest (Michelin Pilot Sport 4 S, XL).

3 tires in 255/30R20

Sort by the spec you care about.

LoadRevs/miSource
Michelin Pilot Sport 4 SPerformanceXL · 92(Y)26.1023.39.51,389798Spec page
Toyo Proxes Sport 2PerformanceXL · 92(Y)26.1024.59.11,389797Spec page
Michelin Pilot Sport 4 SPerformanceXL · 92Y26.1025.19.51,389798Spec page

Is 255/30R20 a 26-inch tire?

≈26″

Yes. The size code works out to 26.02″, and the 3 tires here publish 26.10″, so people call it a 26.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

SizeDiameter ″vs 255/30R20Difference
235/30R2025.55-0.47″-1.8%
285/25R2025.61-0.41″-1.6%
245/30R2025.79-0.24″-0.9%
295/25R2025.81-0.22″-0.8%
305/25R2026.00-0.02″-0.1%
225/35R2026.20+0.18″+0.7%
265/30R2026.26+0.24″+0.9%
325/25R2026.40+0.37″+1.4%
235/35R2026.48+0.45″+1.7%
275/30R2026.50+0.47″+1.8%

How to read 255/30R20

How to read any tire size

255/30R20 92Y as printed on the tire sidewall, with each part numbered255/30R20 92Y123456
How 255/30R20 92Y is printed on the sidewall. It's the most common code among the 3 tires here (2 of them); tires in this size come in other load and speed ratings too.
1255Section width

255 mm across the widest point, or 10.04 inches. Every 255 size

230Aspect ratio

A percentage, not a measurement: the sidewall is 30% as tall as the tire is wide, which is 76.5 mm or 3.01 inches.

3RConstruction

Radial construction.

420Wheel diameter

Mounts on a 20-inch wheel. Approved wheel widths run 8.5″ to 9.5″.

592Load index

Each tire carries up to 1,389 lb (630 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

XLExtra load

Printed after the size.

SpecificationInchesMetric
Overall diameter26.02661 mm
Section width10.04255 mm
Sidewall height3.0176.5 mm
Circumference81.82,077 mm
Revolutions per mile (calculated, unloaded)775.0482 per km
Revolutions per mile (published by manufacturers)797–798495–496 per km
Approved wheel width8.5–9.5216–241 mm

Speedometer error after switching to 255/30R20

Your actual speed– mph

Questions about 255/30R20

What is 255/30R20 in inches?

26.02 inches tall, 10.04 inches wide, on a 20-inch wheel. Written in inches, that is roughly 26.0×10.0R20.

How much does a 255/30R20 tire weigh?

Between 23.3 lb and 25.1 lb for the 3 tires listed here. The lightest is the Michelin Pilot Sport 4 S (XL); the heaviest is the Michelin Pilot Sport 4 S (XL).

What wheel width do I need for 255/30R20?

Manufacturers approve 8.5–9.5″ wide wheels for this size.

How many revolutions per mile does a 255/30R20 make?

Published figures run 797–798 revolutions per mile. The calculated figure is 775.0, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 255/30R20 than 305/25R20?

0.02 inches taller on paper (26.02″ vs 26.00″), which raises the axle about 0.01″. Your speedometer will read about 0.1% slow.