235/45R21 in inches

A 235/45R21 tire is 29.3″ tall and 9.3″ wide, and fits a 21″ wheel. In inches it is written 29.3×9.3R21.

Diameter29.33″

Width9.25″

Sidewall4.16″

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

Manufacturer data

How tall 235/45R21 tires really are

Heights published by Michelin for all 5 tires in this size. Their published revolutions per mile work out to 28.4″ under load (below).

Real 235/45R21 tires measure 29.30–29.33″, against 29.33″ from the size code. They run both taller and shorter than the size code.

Height under load28.4″

Published revs per mile (709) mean the tire rolls like a 28.4″ tire on the vehicle. Use this for speedometer calibration.

Weight spread28.7–30.1 lb

The lightest (Michelin e.Primacy All Season, XL) is 1.4 lb lighter per corner than the heaviest (Michelin Pilot Sport 4 SUV, XL).

5 tires in 235/45R21

Sort by the spec you care about.

	Load					Revs/mi	Source
Michelin e.Primacy All SeasonTouring	XL · 101W	29.30	28.7	8.5	1,819	709	Spec page
Michelin X-Ice SnowWinter	XL · 101H	29.33	28.8	10.5	1,819	709	Spec page
Michelin Pilot Sport 4 SUVPerformance	XL · 101Y	29.30	29.3	9.5	1,819	709	Spec page
Michelin X-Ice Snow+Winter	XL · 101H	29.33	29.6	10.5	1,819	709	Spec page
Michelin Pilot Sport 4 SUVPerformance	XL · 101Y	29.30	30.1	9.5	1,819	709	Spec page

Is 235/45R21 a 29-inch tire?

≈29″

Yes. The size code works out to 29.33″, and the 5 tires here publish 29.30–29.33″, 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 235/45R21	Difference
335/30R21	28.91	-0.41″	-1.4%
225/45R21	28.97	-0.35″	-1.2%
255/40R21	29.03	-0.30″	-1.0%
295/35R21	29.13	-0.20″	-0.7%
345/30R21	29.15	-0.18″	-0.6%
265/40R21	29.35	+0.02″	+0.1%
305/35R21	29.41	+0.08″	+0.3%
275/40R21	29.66	+0.33″	+1.1%
245/45R21	29.68	+0.35″	+1.2%
315/35R21	29.68	+0.35″	+1.2%

How to read 235/45R21

How to read any tire size

How 235/45R21 101Y is printed on the sidewall. It's the most common code among the 5 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

245Aspect ratio

A percentage, not a measurement: the sidewall is 45% as tall as the tire is wide, which is 105.8 mm or 4.16 inches.

3RConstruction

Radial construction.

421Wheel diameter

Mounts on a 21-inch wheel. Approved wheel widths run 7.5″ to 9.0″.

5101Load index

Each tire carries up to 1,819 lb (825 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	29.33	745 mm
Section width	9.25	235 mm
Sidewall height	4.16	105.8 mm
Circumference	92.1	2,340 mm
Revolutions per mile (calculated, unloaded)	687.7	427 per km
Revolutions per mile (published by manufacturers)	709	441 per km
Approved wheel width	7.5–9.0	191–229 mm

Speedometer error after switching to 235/45R21

Your actual speed– mph

Questions about 235/45R21

What is 235/45R21 in inches?

29.33 inches tall, 9.25 inches wide, on a 21-inch wheel. Written in inches, that is roughly 29.3×9.3R21.

How much does a 235/45R21 tire weigh?

Between 28.7 lb and 30.1 lb for the 5 tires listed here. The lightest is the Michelin e.Primacy All Season (XL); the heaviest is the Michelin Pilot Sport 4 SUV (XL).

What wheel width do I need for 235/45R21?

Manufacturers approve 7.5–9.0″ wide wheels for this size.

How many revolutions per mile does a 235/45R21 make?

Published figures run 709 revolutions per mile. The calculated figure is 687.7, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 235/45R21 than 345/30R21?

0.18 inches taller on paper (29.33″ vs 29.15″), which raises the axle about 0.09″. Your speedometer will read about 0.6% slow.