285/40R20 in inches

A 285/40R20 tire is 29.0″ tall and 11.2″ wide, and fits a 20″ wheel. In inches it is written 29.0×11.2R20.

Diameter28.98″

Width11.22″

Sidewall4.49″

Drawn to scale. Nominal dimensions calculated from the size code.

Manufacturer data

How tall 285/40R20 tires really are

Heights published by Michelin for all 7 tires in this size. Their published revolutions per mile work out to 28.1″ under load (below).

Real 285/40R20 tires measure 28.98–29.00″, against 28.98″ from the size code. They run both taller and shorter than the size code.

Height under load28.1″

Published revs per mile (718) mean the tire rolls like a 28.1″ tire on the vehicle. Use this for speedometer calibration.

Weight spread31.2–34.2 lb

The lightest (Michelin Pilot Alpin 5, XL) is 3.0 lb lighter per corner than the heaviest (Michelin Primacy Tour A/S, XL).

7 tires in 285/40R20

Sort by the spec you care about.

	Load					Revs/mi	Source
Michelin Pilot Alpin 5Winter	XL · 108V	28.98	31.2	9.5	2,205	718	Spec page
Michelin CrossClimate2All-season	XL · 108V	29.00	32.5	10.0	2,205	718	Spec page
Michelin Pilot Alpin 5Winter	XL · 108V	28.98	32.6	9.5	2,205	718	Spec page
Michelin Pilot Alpin 5Winter	XL · 108V	28.98	32.6	9.5	2,205	718	Spec page
Michelin Pilot Sport 4Performance	XL · 108Y	29.00	33.0	9.5	2,205	718	Spec page
Michelin Latitude Sport 3Performance	XL · 108Y	29.00	33.7	8.5	2,205	718	Spec page
Michelin Primacy Tour A/STouring	XL · 108W	29.00	34.2	8.5	2,205	718	Spec page

Is 285/40R20 a 29-inch tire?

≈29″

Yes. The size code works out to 28.98″, and the 7 tires here publish 28.98–29.00″, 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.

Size	Diameter ″	vs 285/40R20	Difference
265/40R20	28.35	-0.63″	-2.2%
305/35R20	28.41	-0.57″	-2.0%
275/40R20	28.66	-0.31″	-1.1%
245/45R20	28.68	-0.30″	-1.0%
315/35R20	28.68	-0.30″	-1.0%
255/45R20	29.04	+0.06″	+0.2%
235/50R20	29.25	+0.28″	+1.0%
295/40R20	29.29	+0.31″	+1.1%
265/45R20	29.39	+0.41″	+1.4%
305/40R20	29.61	+0.63″	+2.2%

How to read 285/40R20

How to read any tire size

How 285/40R20 108V is printed on the sidewall. It's the most common code among the 7 tires here (4 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

240Aspect ratio

A percentage, not a measurement: the sidewall is 40% as tall as the tire is wide, which is 114.0 mm or 4.49 inches.

3RConstruction

Radial construction.

420Wheel diameter

Mounts on a 20-inch wheel. Approved wheel widths run 9.5″ to 11.0″.

5108Load index

Each tire carries up to 2,205 lb (1,000 kg) at its maximum pressure.

6VSpeed rating

Rated for up to 149 mph sustained.

XLExtra load

Printed after the size.

Specification	Inches	Metric
Overall diameter	28.98	736 mm
Section width	11.22	285 mm
Sidewall height	4.49	114.0 mm
Circumference	91.0	2,312 mm
Revolutions per mile (calculated, unloaded)	696.0	432 per km
Revolutions per mile (published by manufacturers)	718	446 per km
Approved wheel width	9.5–11.0	241–279 mm

Speedometer error after switching to 285/40R20

Your actual speed– mph

Questions about 285/40R20

What is 285/40R20 in inches?

28.98 inches tall, 11.22 inches wide, on a 20-inch wheel. Written in inches, that is roughly 29.0×11.2R20.

How much does a 285/40R20 tire weigh?

Between 31.2 lb and 34.2 lb for the 7 tires listed here. The lightest is the Michelin Pilot Alpin 5 (XL); the heaviest is the Michelin Primacy Tour A/S (XL).

What wheel width do I need for 285/40R20?

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

How many revolutions per mile does a 285/40R20 make?

Published figures run 718 revolutions per mile. The calculated figure is 696.0, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 285/40R20 than 315/35R20?

0.30 inches taller on paper (28.98″ vs 28.68″), which raises the axle about 0.15″. Your speedometer will read about 1.0% slow.