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345/30R21 in inches

A 345/30R21 tire is 29.1″ tall and 13.6″ wide, and fits a 21″ wheel. In inches it is written 29.1×13.6R21.

Diameter29.15″
Width13.58″
Sidewall4.07″
345/30R21 drawn to scale: 29.15 inch diameter, 4.07 inch sidewall, 21 inch wheel, 13.58 inch tread width21″ wheel4.07″29.15″ overall13.58″ wideSide view
Drawn to scale. Nominal dimensions calculated from the size code.
Manufacturer data

How tall 345/30R21 tires really are

Heights published by Michelin for all 2 tires in this size. Their published revolutions per mile work out to 28.3″ under load (below).

Real 345/30R21 tires measure 29.20″, against 29.15″ from the size code. Every one runs taller than the size code.

Height under load28.3″

Published revs per mile (713) mean the tire rolls like a 28.3″ tire on the vehicle. Use this for speedometer calibration.

Weight spread32.8–33.1 lb

The lightest (Michelin Pilot Sport Cup 2 R, XL) is 0.3 lb lighter per corner than the heaviest (Michelin Pilot Sport Cup 2 Connect, XL).

2 tires in 345/30R21

Sort by the spec you care about.

LoadRevs/miSource
Michelin Pilot Sport Cup 2 RPerformanceXL · 111(Y)29.2032.85.52,403713Spec page
Michelin Pilot Sport Cup 2 ConnectPerformanceXL · 111(Y)29.2033.17.22,403713Spec page

Is 345/30R21 a 29-inch tire?

≈29″

Yes. The size code works out to 29.15″, and the 2 tires here publish 29.20″, 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 345/30R21Difference
325/30R2128.68-0.47″-1.6%
245/40R2128.72-0.43″-1.5%
285/35R2128.85-0.30″-1.0%
335/30R2128.91-0.24″-0.8%
225/45R2128.97-0.18″-0.6%
255/40R2129.03-0.12″-0.4%
295/35R2129.13-0.02″-0.1%
235/45R2129.33+0.18″+0.6%
265/40R2129.35+0.20″+0.7%
305/35R2129.41+0.26″+0.9%

How to read 345/30R21

How to read any tire size

345/30R21 111Y as printed on the tire sidewall, with each part numbered345/30R21 111Y123456
How 345/30R21 111Y is printed on the sidewall. It's the most common code among the 2 tires here; tires in this size come in other load and speed ratings too.
1345Section width

345 mm across the widest point, or 13.58 inches. Every 345 size

230Aspect ratio

A percentage, not a measurement: the sidewall is 30% as tall as the tire is wide, which is 103.5 mm or 4.07 inches.

3RConstruction

Radial construction.

421Wheel diameter

Mounts on a 21-inch wheel. Approved wheel widths run 11.5″ to 12.5″.

5111Load index

Each tire carries up to 2,403 lb (1,090 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

XLExtra load

Printed after the size.

SpecificationInchesMetric
Overall diameter29.15740 mm
Section width13.58345 mm
Sidewall height4.07103.5 mm
Circumference91.62,326 mm
Revolutions per mile (calculated, unloaded)691.9430 per km
Revolutions per mile (published by manufacturers)713443 per km
Approved wheel width11.5–12.5292–318 mm

Speedometer error after switching to 345/30R21

Your actual speed– mph

Questions about 345/30R21

What is 345/30R21 in inches?

29.15 inches tall, 13.58 inches wide, on a 21-inch wheel. Written in inches, that is roughly 29.1×13.6R21.

How much does a 345/30R21 tire weigh?

Between 32.8 lb and 33.1 lb for the 2 tires listed here. The lightest is the Michelin Pilot Sport Cup 2 R (XL); the heaviest is the Michelin Pilot Sport Cup 2 Connect (XL).

What wheel width do I need for 345/30R21?

Manufacturers approve 11.5–12.5″ wide wheels for this size.

How many revolutions per mile does a 345/30R21 make?

Published figures run 713 revolutions per mile. The calculated figure is 691.9, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 345/30R21 than 295/35R21?

0.02 inches taller on paper (29.15″ vs 29.13″), which raises the axle about 0.01″. Your speedometer will read about 0.1% slow.