295/40R21 Tire Size
295/40R21 diameter, sidewall, revolutions per mile, and plus-sizing options.
The 295/40R21 tire size breaks down as: 295 mm section width, 40% aspect ratio, and a 21-inch rim. Below are its real, calculated dimensions.
295/40R21 Calculated Dimensions
| Metric | Value |
|---|---|
| Overall diameter | 30.3 in (769 mm) |
| Sidewall height | 4.6 in (118 mm) |
| Circumference | 95.2 in (2417 mm) |
| Revolutions per mile | 666 |
Typical Fitment
295/40R21 is most often found on full-size performance SUVs. Always confirm against the door-jamb placard or owner manual before fitting.
Plus-Sizing Alternatives
These sizes keep the overall diameter close to 295/40R21, so speedometer and gearing stay near stock:
| Size | Diameter | Diameter change |
|---|---|---|
| 305/40R21 | 30.61 in | +1.0% |
| 305/35R22 | 30.41 in | +0.4% |
| 315/30R23 | 30.44 in | +0.5% |
Speedometer Note
If you fit a 305/40R21 instead of 295/40R21, the diameter changes by +1.0%. A taller tire makes your speedometer read low — at a true 60 mph it would show roughly 59 mph. A shorter tire has the opposite effect, so the gauge reads high.
Use the tire calculator to compare 295/40R21 against any other size and see the exact diameter and speedometer difference.
Frequently Asked Questions
What does 295/40R21 mean?
295/40R21 means a 295 mm wide tire with a 40% sidewall aspect ratio mounted on a 21-inch rim. The aspect ratio is the sidewall height as a percentage of the width.
Can I plus-size from 295/40R21?
Yes, as long as the replacement keeps the overall diameter close to stock so the speedometer stays accurate. Common plus-size moves from 295/40R21 are 305/40R21, 305/35R22, 315/30R23.
Will 295/40R21 affect my speedometer?
Only if it differs in diameter from your original size. A taller tire reads low; a shorter tire reads high. Compare the two sizes with the calculator to find the percentage.