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255/35R21 in inches

A 255/35R21 tire is 28.0″ tall and 10.0″ wide, and fits a 21″ wheel. In inches it is written 28.0×10.0R21.

Diameter28.03″
Width10.04″
Sidewall3.51″
255/35R21 drawn to scale: 28.03 inch diameter, 3.51 inch sidewall, 21 inch wheel, 10.04 inch tread width21″ wheel3.51″28.03″ overall10.04″ wideSide view
Drawn to scale. Nominal dimensions calculated from the size code.
Manufacturer data

How tall 255/35R21 tires really are

Heights published by Michelin for all 4 tires in this size. Their published revolutions per mile work out to 27.1″ under load (below).

Real 255/35R21 tires measure 27.99–28.00″, against 28.03″ from the size code. Every one runs shorter than the size code.

Height under load27.1″

Published revs per mile (743) mean the tire rolls like a 27.1″ tire on the vehicle. Use this for speedometer calibration.

Weight spread26.9–28.6 lb

The lightest (Michelin Pilot Alpin PA4, XL) is 1.7 lb lighter per corner than the heaviest (Michelin X-Ice Snow+, XL).

4 tires in 255/35R21

Sort by the spec you care about.

LoadRevs/miSource
Michelin Pilot Alpin PA4WinterXL · 98W27.9926.910.51,653743Spec page
Michelin Pilot Sport 4 SPerformanceXL · 98(Y)28.0027.79.51,653743Spec page
Michelin Pilot Sport All-Season 4PerformanceXL · 98W28.0028.09.01,653743Spec page
Michelin X-Ice Snow+WinterXL · 98H27.9928.610.51,653743Spec page

Is 255/35R21 a 28-inch tire?

≈28″

Yes. The size code works out to 28.03″, and the 4 tires here publish 27.99–28.00″, so people call it a 28.

All 28-inch tire sizes, on every wheel size.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

SizeDiameter ″vs 255/35R21Difference
275/30R2127.50-0.53″-1.9%
285/30R2127.73-0.30″-1.1%
245/35R2127.75-0.28″-1.0%
345/25R2127.79-0.24″-0.8%
295/30R2127.97-0.06″-0.2%
355/25R2127.99-0.04″-0.1%
305/30R2128.20+0.18″+0.6%
265/35R2128.30+0.28″+1.0%
315/30R2128.44+0.41″+1.5%
275/35R2128.58+0.55″+2.0%

How to read 255/35R21

How to read any tire size

255/35R21 98W as printed on the tire sidewall, with each part numbered255/35R21 98W123456
How 255/35R21 98W is printed on the sidewall. It's the most common code among the 4 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

235Aspect ratio

A percentage, not a measurement: the sidewall is 35% as tall as the tire is wide, which is 89.3 mm or 3.51 inches.

3RConstruction

Radial construction.

421Wheel diameter

Mounts on a 21-inch wheel. Approved wheel widths run 8.5″ to 10.0″.

598Load index

Each tire carries up to 1,653 lb (750 kg) at its maximum pressure.

6WSpeed rating

Rated for up to 168 mph sustained.

XLExtra load

Printed after the size.

SpecificationInchesMetric
Overall diameter28.03712 mm
Section width10.04255 mm
Sidewall height3.5189.3 mm
Circumference88.12,236 mm
Revolutions per mile (calculated, unloaded)719.6447 per km
Revolutions per mile (published by manufacturers)743462 per km
Approved wheel width8.5–10.0216–254 mm

Speedometer error after switching to 255/35R21

Your actual speed– mph

Questions about 255/35R21

What is 255/35R21 in inches?

28.03 inches tall, 10.04 inches wide, on a 21-inch wheel. Written in inches, that is roughly 28.0×10.0R21.

How much does a 255/35R21 tire weigh?

Between 26.9 lb and 28.6 lb for the 4 tires listed here. The lightest is the Michelin Pilot Alpin PA4 (XL); the heaviest is the Michelin X-Ice Snow+ (XL).

What wheel width do I need for 255/35R21?

Manufacturers approve 8.5–10.0″ wide wheels for this size.

How many revolutions per mile does a 255/35R21 make?

Published figures run 743 revolutions per mile. The calculated figure is 719.6, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 255/35R21 than 355/25R21?

0.04 inches taller on paper (28.03″ vs 27.99″), which raises the axle about 0.02″. Your speedometer will read about 0.1% slow.