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345/25R21 in inches

A 345/25R21 tire is 27.8″ tall and 13.6″ wide, and fits a 21″ wheel. In inches it is written 27.8×13.6R21.

Diameter27.79″
Width13.58″
Sidewall3.40″
345/25R21 drawn to scale: 27.79 inch diameter, 3.40 inch sidewall, 21 inch wheel, 13.58 inch tread width21″ wheel3.40″27.79″ overall13.58″ wideSide view
Drawn to scale. Nominal dimensions calculated from the size code.
Manufacturer data

How tall 345/25R21 tires really are

Heights published by Michelin for all 3 tires in this size. Their published revolutions per mile work out to 26.9″ under load (below).

Real 345/25R21 tires measure 27.60–27.76″, against 27.79″ from the size code. Every one runs shorter than the size code.

  1. Michelin Pilot Alpin PA427.76″ −0.03″
  2. Michelin Pilot Sport Cup 2 R27.70″ −0.09″
  3. Michelin Pilot Sport 4 S27.60″ −0.19″
Each bar runs from the size code's 27.79″ (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 load26.9″

Published revs per mile (749) mean the tire rolls like a 26.9″ tire on the vehicle. Use this for speedometer calibration.

Weight spread34.0–37.5 lb

The lightest (Michelin Pilot Sport Cup 2 R, XL) is 3.5 lb lighter per corner than the heaviest (Michelin Pilot Sport 4 S, XL).

3 tires in 345/25R21

Sort by the spec you care about.

LoadRevs/miSource
Michelin Pilot Sport Cup 2 RPerformanceXL · 104(Y)27.7034.05.01,984749Spec page
Michelin Pilot Alpin PA4WinterSL · 101W27.7634.810.51,819749Spec page
Michelin Pilot Sport 4 SPerformanceXL · 104(Y)27.6037.57.51,984749Spec page

Is 345/25R21 a 28-inch tire?

≈28″

Yes. The size code works out to 27.79″, and the 3 tires here publish 27.60–27.76″, 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.

SizeDiameter ″vs 345/25R21Difference
265/30R2127.26-0.53″-1.9%
325/25R2127.40-0.39″-1.4%
275/30R2127.50-0.30″-1.1%
285/30R2127.73-0.06″-0.2%
245/35R2127.75-0.04″-0.1%
295/30R2127.97+0.18″+0.6%
355/25R2127.99+0.20″+0.7%
255/35R2128.03+0.24″+0.8%
305/30R2128.20+0.41″+1.5%
265/35R2128.30+0.51″+1.8%

How to read 345/25R21

How to read any tire size

345/25R21 104Y as printed on the tire sidewall, with each part numbered345/25R21 104Y123456
How 345/25R21 104Y 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.
1345Section width

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

225Aspect ratio

A percentage, not a measurement: the sidewall is 25% as tall as the tire is wide, which is 86.3 mm or 3.40 inches.

3RConstruction

Radial construction.

421Wheel diameter

Mounts on a 21-inch wheel. Approved wheel widths run 12.0″ to 13.0″.

5104Load index

Each tire carries up to 1,984 lb (900 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

XLExtra load

Printed after the size. In this size the XL tires carry up to 1,984 lb each and the standard-load tires up to 1,819 lb, as published.

SpecificationInchesMetric
Overall diameter27.79706 mm
Section width13.58345 mm
Sidewall height3.4086.3 mm
Circumference87.32,218 mm
Revolutions per mile (calculated, unloaded)725.7451 per km
Revolutions per mile (published by manufacturers)749465 per km
Approved wheel width12.0–13.0305–330 mm

Speedometer error after switching to 345/25R21

Your actual speed– mph

Questions about 345/25R21

What is 345/25R21 in inches?

27.79 inches tall, 13.58 inches wide, on a 21-inch wheel. Written in inches, that is roughly 27.8×13.6R21.

How much does a 345/25R21 tire weigh?

Between 34.0 lb and 37.5 lb for the 3 tires listed here. The lightest is the Michelin Pilot Sport Cup 2 R (XL); the heaviest is the Michelin Pilot Sport 4 S (XL).

What wheel width do I need for 345/25R21?

Manufacturers approve 12.0–13.0″ wide wheels for this size.

How many revolutions per mile does a 345/25R21 make?

Published figures run 749 revolutions per mile. The calculated figure is 725.7, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 345/25R21 than 245/35R21?

0.04 inches taller on paper (27.79″ vs 27.75″), which raises the axle about 0.02″. Your speedometer will read about 0.1% slow.