235/40R20 in inches

A 235/40R20 tire is 27.4″ tall and 9.3″ wide, and fits a 20″ wheel. In inches it is written 27.4×9.3R20.

Diameter27.40″

Width9.25″

Sidewall3.70″

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

Manufacturer data

How tall 235/40R20 tires really are

Heights published by Michelin for all 3 tires in this size. Their published revolutions per mile work out to 26.6″ under load (below).

Real 235/40R20 tires measure 27.40–27.70″, against 27.40″ from the size code. They run both taller and shorter than the size code.

Michelin Pilot Sport All-Season 427.70″ +0.30″
Michelin Pilot Sport 4 S27.40″ −0.00″
Michelin Pilot Sport EV27.40″ −0.00″

Each bar runs from the size code's 27.40″ (the orange line) to the model's published height. The track spans 1.0″. Where a model comes in several load ranges, the darker part shows its range of heights; the number after the name is how many versions it comes in.

Height under load26.6″

Published revs per mile (759) mean the tire rolls like a 26.6″ tire on the vehicle. Use this for speedometer calibration.

Weight spread25.0–26.9 lb

The lightest (Michelin Pilot Sport EV, XL) is 1.9 lb lighter per corner than the heaviest (Michelin Pilot Sport All-Season 4, XL).

3 tires in 235/40R20

Sort by the spec you care about.

	Load					Revs/mi	Source
Michelin Pilot Sport EVPerformance	XL · 96(Y)	27.40	25.0	8.5	1,565	759	Spec page
Michelin Pilot Sport 4 SPerformance	XL · 96(Y)	27.40	25.4	9.5	1,565	759	Spec page
Michelin Pilot Sport All-Season 4Performance	XL · 96Y	27.70	26.9	10.0	1,565	759	Spec page

Is 235/40R20 a 28-inch tire?

≈28″

Close. The size code works out to 27.40″, and the 3 tires here publish 27.40–27.70″, 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.

Size	Diameter ″	vs 235/40R20	Difference
295/30R20	26.97	-0.43″	-1.6%
255/35R20	27.03	-0.37″	-1.4%
225/40R20	27.09	-0.31″	-1.1%
305/30R20	27.20	-0.20″	-0.7%
265/35R20	27.30	-0.10″	-0.4%
315/30R20	27.44	+0.04″	+0.1%
275/35R20	27.58	+0.18″	+0.6%
215/45R20	27.62	+0.22″	+0.8%
325/30R20	27.68	+0.28″	+1.0%
245/40R20	27.72	+0.31″	+1.1%

How to read 235/40R20

How to read any tire size

How 235/40R20 96Y 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.

1235Section width

235 mm across the widest point, or 9.25 inches. Every 235 size

240Aspect ratio

A percentage, not a measurement: the sidewall is 40% as tall as the tire is wide, which is 94.0 mm or 3.70 inches.

3RConstruction

Radial construction.

420Wheel diameter

Mounts on a 20-inch wheel. Approved wheel widths run 8.0″ to 9.5″.

596Load index

Each tire carries up to 1,565 lb (710 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

XLExtra load

Printed after the size.

Specification	Inches	Metric
Overall diameter	27.40	696 mm
Section width	9.25	235 mm
Sidewall height	3.70	94.0 mm
Circumference	86.1	2,187 mm
Revolutions per mile (calculated, unloaded)	736.0	457 per km
Revolutions per mile (published by manufacturers)	759	472 per km
Approved wheel width	8.0–9.5	203–241 mm

Speedometer error after switching to 235/40R20

Your actual speed– mph

Questions about 235/40R20

What is 235/40R20 in inches?

27.40 inches tall, 9.25 inches wide, on a 20-inch wheel. Written in inches, that is roughly 27.4×9.3R20.

How much does a 235/40R20 tire weigh?

Between 25.0 lb and 26.9 lb for the 3 tires listed here. The lightest is the Michelin Pilot Sport EV (XL); the heaviest is the Michelin Pilot Sport All-Season 4 (XL).

What wheel width do I need for 235/40R20?

Manufacturers approve 8.0–9.5″ wide wheels for this size.

How many revolutions per mile does a 235/40R20 make?

Published figures run 759 revolutions per mile. The calculated figure is 736.0, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 235/40R20 than 265/35R20?

0.10 inches taller on paper (27.40″ vs 27.30″), which raises the axle about 0.05″. Your speedometer will read about 0.4% slow.