tireheight.com245/40R21 in inches
A 245/40R21 tire is 28.7″ tall and 9.6″ wide, and fits a 21″ wheel. In inches it is written 28.7×9.6R21.
How tall 245/40R21 tires really are
Heights published by Michelin for all 6 tires in this size. Their published revolutions per mile work out to 26.9–27.8″ under load (below).
Real 245/40R21 tires measure 28.70″, against 28.72″ from the size code. They run both taller and shorter than the size code.
Published revs per mile (725–750) mean the tire rolls like a 26.9–27.8″ tire on the vehicle. Use this for speedometer calibration.
The lightest (Michelin Pilot Sport S 5, SL) is 3.5 lb lighter per corner than the heaviest (Michelin Pilot Super Sport, SL).
6 tires in 245/40R21
Sort by the spec you care about.
| Load | Revs/mi | Source | |||||
|---|---|---|---|---|---|---|---|
| Michelin Pilot Sport S 5Performance | SL · 96Y | 28.70 | 27.1 | 8.5 | 1,565 | 725 | Spec page |
| Michelin Primacy Tour A/STouring | XL · 100V | 28.70 | 27.9 | 8.5 | 1,764 | 725 | Spec page |
| Michelin Pilot Sport 4 SPerformance | XL · 100(Y) | 28.70 | 28.9 | 9.5 | 1,764 | 750 | Spec page |
| Michelin Pilot Sport All-Season 4Performance | XL · 100Y | 28.70 | 29.2 | 10.0 | 1,764 | 725 | Spec page |
| Michelin Pilot Sport EVPerformance | XL · 100Y | 28.70 | 29.5 | 8.5 | 1,764 | 725 | Spec page |
| Michelin Pilot Super SportPerformance | SL · 96Y | 28.70 | 30.6 | 9.5 | 1,565 | 725 | Spec page |
Is 245/40R21 a 29-inch tire?
Yes. The size code works out to 28.72″, and the 6 tires here publish 28.70″, 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.
How to read 245/40R21
A percentage, not a measurement: the sidewall is 40% as tall as the tire is wide, which is 98.0 mm or 3.86 inches.
Radial construction.
Mounts on a 21-inch wheel. Approved wheel widths run 8.0″ to 9.5″.
Each tire carries up to 1,764 lb (800 kg) at its maximum pressure.
Rated for up to 186 mph sustained.
Printed after the size. In this size the XL tires carry up to 1,764 lb each and the standard-load tires up to 1,565 lb, as published.
| Specification | Inches | Metric |
|---|---|---|
| Overall diameter | 28.72 | 729 mm |
| Section width | 9.65 | 245 mm |
| Sidewall height | 3.86 | 98.0 mm |
| Circumference | 90.2 | 2,291 mm |
| Revolutions per mile (calculated, unloaded) | 702.3 | 436 per km |
| Revolutions per mile (published by manufacturers) | 725–750 | 450–466 per km |
| Approved wheel width | 8.0–9.5 | 203–241 mm |
Speedometer error after switching to 245/40R21
Questions about 245/40R21
What is 245/40R21 in inches?
28.72 inches tall, 9.65 inches wide, on a 21-inch wheel. Written in inches, that is roughly 28.7×9.6R21.
How much does a 245/40R21 tire weigh?
Between 27.1 lb and 30.6 lb for the 6 tires listed here. The lightest is the Michelin Pilot Sport S 5 (SL); the heaviest is the Michelin Pilot Super Sport (SL).
What wheel width do I need for 245/40R21?
Manufacturers approve 8.0–9.5″ wide wheels for this size.
How many revolutions per mile does a 245/40R21 make?
Published figures run 725–750 revolutions per mile. The calculated figure is 702.3, but manufacturers measure the tire under load, where it rolls on a smaller radius.
How much taller is 245/40R21 than 325/30R21?
0.04 inches taller on paper (28.72″ vs 28.68″), which raises the axle about 0.02″. Your speedometer will read about 0.1% slow.