275/40R21 tire size
A 275/40R21 tire is 29.7 inches tall and 10.8 inches wide. Here are its full dimensions, what the numbers mean, and the sizes you can swap it for.
- Overall diameter
- 29.66″ (753 mm)
- Section width
- 10.83″ (275 mm)
- Sidewall height
- 4.33″ (110 mm)
- Wheel diameter
- 21″
- Circumference
- 93.2″
- Revolutions per mile
- 680
What 275/40R21 means
- 275: the tire is 275 mm (10.8 in) wide from sidewall to sidewall.
- 40: the sidewall is 40% of the width, 110.0 mm (4.33 in) tall.
- R: radial construction, used by almost every modern tire.
- 21: it fits a 21-inch wheel.
Overall diameter = 21 + 2 × 4.33 = 29.66 inches.
Sizes equivalent to 275/40R21
These sizes are within 3% of the overall diameter, the usual limit for swapping without speedometer problems.
| Size | Diameter | Difference | Speedometer at 60 mph |
|---|---|---|---|
| 285/30R23 | 29.7″ | +0.2% | 60.1 mph actual |
| 275/35R22 | 29.6″ | -0.3% | 59.8 mph actual |
| 275/30R23 | 29.5″ | -0.6% | 59.7 mph actual |
| 285/35R22 | 29.9″ | +0.7% | 60.4 mph actual |
| 295/30R23 | 30.0″ | +1.0% | 60.6 mph actual |
| 265/40R21 | 29.3″ | -1.1% | 59.4 mph actual |
| 285/40R21 | 30.0″ | +1.1% | 60.6 mph actual |
| 265/35R22 | 29.3″ | -1.2% | 59.3 mph actual |
| 255/35R23 | 30.0″ | +1.2% | 60.7 mph actual |
| 255/40R22 | 30.0″ | +1.2% | 60.7 mph actual |
See every common size side by side in the tire size chart.
Questions
What is 275/40R21 in inches?
A 275/40R21 tire is about 29.7 inches tall (753 mm) and 10.8 inches wide, on a 21-inch wheel. In flotation sizing that's roughly 29.7x10.8R21.
How tall is a 275/40R21 tire?
The overall diameter is 29.66 inches: the 21-inch wheel plus two 4.33-inch sidewalls. Actual tires vary by a few tenths of an inch between brands and models.
How many revolutions per mile does a 275/40R21 make?
About 680 revolutions per mile, from a circumference of 93.2 inches.
