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285/35R21 in inches

A 285/35R21 tire is 28.9″ tall and 11.2″ wide, and fits a 21″ wheel. In inches it is written 28.9×11.2R21.

Diameter28.85″
Width11.22″
Sidewall3.93″
285/35R21 drawn to scale: 28.85 inch diameter, 3.93 inch sidewall, 21 inch wheel, 11.22 inch tread width21″ wheel3.93″28.85″ overall11.22″ wideSide view
Drawn to scale. Nominal dimensions calculated from the size code.
Manufacturer data

How tall 285/35R21 tires really are

Heights published by Michelin and Toyo for all 3 tires in this size. Their published revolutions per mile work out to 28.0″ under load (below).

Real 285/35R21 tires measure 28.86–28.90″, against 28.85″ from the size code. They run both taller and shorter than the size code.

Height under load28.0″

Published revs per mile (720–721) mean the tire rolls like a 28.0″ tire on the vehicle. Use this for speedometer calibration.

Weight spread29.8–35.7 lb

The lightest (Michelin Pilot Super Sport, XL) is 5.9 lb lighter per corner than the heaviest (Toyo Observe G3-Ice, XL).

3 tires in 285/35R21

Sort by the spec you care about.

LoadRevs/miSource
Michelin Pilot Super SportPerformanceXL · 105Y28.9029.810.02,039721Spec page
Toyo Proxes Sport 2PerformanceXL · 105Y28.9032.89.22,039720Spec page
Toyo Observe G3-IceWinterXL · 105T28.8635.712.02,039720Spec page

Is 285/35R21 a 29-inch tire?

≈29″

Yes. The size code works out to 28.85″, and the 3 tires here publish 28.86–28.90″, so people call it a 29.

All 29-inch tire sizes, on every wheel size.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

SizeDiameter ″vs 285/35R21Difference
315/30R2128.44-0.41″-1.4%
275/35R2128.58-0.28″-1.0%
325/30R2128.68-0.18″-0.6%
245/40R2128.72-0.14″-0.5%
335/30R2128.91+0.06″+0.2%
225/45R2128.97+0.12″+0.4%
255/40R2129.03+0.18″+0.6%
295/35R2129.13+0.28″+1.0%
345/30R2129.15+0.30″+1.0%
235/45R2129.33+0.47″+1.6%

How to read 285/35R21

How to read any tire size

285/35R21 105Y as printed on the tire sidewall, with each part numbered285/35R21 105Y123456
How 285/35R21 105Y 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.
1285Section width

285 mm across the widest point, or 11.22 inches. Every 285 size

235Aspect ratio

A percentage, not a measurement: the sidewall is 35% as tall as the tire is wide, which is 99.8 mm or 3.93 inches.

3RConstruction

Radial construction.

421Wheel diameter

Mounts on a 21-inch wheel. Approved wheel widths run 9.5″ to 11.0″.

5105Load index

Each tire carries up to 2,039 lb (925 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

XLExtra load

Printed after the size.

SpecificationInchesMetric
Overall diameter28.85733 mm
Section width11.22285 mm
Sidewall height3.9399.8 mm
Circumference90.62,302 mm
Revolutions per mile (calculated, unloaded)699.0434 per km
Revolutions per mile (published by manufacturers)720–721447–448 per km
Approved wheel width9.5–11.0241–279 mm

Speedometer error after switching to 285/35R21

Your actual speed– mph

Questions about 285/35R21

What is 285/35R21 in inches?

28.85 inches tall, 11.22 inches wide, on a 21-inch wheel. Written in inches, that is roughly 28.9×11.2R21.

How much does a 285/35R21 tire weigh?

Between 29.8 lb and 35.7 lb for the 3 tires listed here. The lightest is the Michelin Pilot Super Sport (XL); the heaviest is the Toyo Observe G3-Ice (XL).

What wheel width do I need for 285/35R21?

Manufacturers approve 9.5–11.0″ wide wheels for this size.

How many revolutions per mile does a 285/35R21 make?

Published figures run 720–721 revolutions per mile. The calculated figure is 699.0, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 285/35R21 than 245/40R21?

0.14 inches taller on paper (28.85″ vs 28.72″), which raises the axle about 0.07″. Your speedometer will read about 0.5% slow.