285/55R20 Tire Size
285/55R20 diameter, sidewall, revolutions per mile, and plus-sizing options.
The 285/55R20 tire size breaks down as: 285 mm section width, 55% aspect ratio, and a 20-inch rim. Below are its real, calculated dimensions.
285/55R20 Calculated Dimensions
| Metric | Value |
|---|---|
| Overall diameter | 32.3 in (822 mm) |
| Sidewall height | 6.2 in (157 mm) |
| Circumference | 101.6 in (2581 mm) |
| Revolutions per mile | 624 |
Typical Fitment
285/55R20 is most often found on full-size SUVs and pickups. Always confirm against the door-jamb placard or owner manual before fitting.
Plus-Sizing Alternatives
These sizes keep the overall diameter close to 285/55R20, so speedometer and gearing stay near stock:
| Size | Diameter | Diameter change |
|---|---|---|
| 295/55R20 | 32.78 in | +1.3% |
| 295/50R21 | 32.61 in | +0.8% |
| 305/45R22 | 32.81 in | +1.4% |
Speedometer Note
If you fit a 295/55R20 instead of 285/55R20, the diameter changes by +1.3%. 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 285/55R20 against any other size and see the exact diameter and speedometer difference.
Frequently Asked Questions
What does 285/55R20 mean?
285/55R20 means a 285 mm wide tire with a 55% sidewall aspect ratio mounted on a 20-inch rim. The aspect ratio is the sidewall height as a percentage of the width.
Can I plus-size from 285/55R20?
Yes, as long as the replacement keeps the overall diameter close to stock so the speedometer stays accurate. Common plus-size moves from 285/55R20 are 295/55R20, 295/50R21, 305/45R22.
Will 285/55R20 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.