285/65R20 Tire Size
285/65R20 diameter, sidewall, revolutions per mile, and plus-sizing options.
The 285/65R20 tire size breaks down as: 285 mm section width, 65% aspect ratio, and a 20-inch rim. Below are its real, calculated dimensions.
285/65R20 Calculated Dimensions
| Metric | Value |
|---|---|
| Overall diameter | 34.6 in (879 mm) |
| Sidewall height | 7.3 in (185 mm) |
| Circumference | 108.7 in (2760 mm) |
| Revolutions per mile | 583 |
Typical Fitment
285/65R20 is most often found on three-quarter-ton pickups. Always confirm against the door-jamb placard or owner manual before fitting.
Plus-Sizing Alternatives
These sizes keep the overall diameter close to 285/65R20, so speedometer and gearing stay near stock:
| Size | Diameter | Diameter change |
|---|---|---|
| 295/65R20 | 35.10 in | +1.5% |
| 295/60R21 | 34.94 in | +1.0% |
| 305/50R22 | 34.01 in | -1.7% |
Speedometer Note
If you fit a 295/65R20 instead of 285/65R20, the diameter changes by +1.5%. 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 285/65R20 against any other size and see the exact diameter and speedometer difference.
Frequently Asked Questions
What does 285/65R20 mean?
285/65R20 means a 285 mm wide tire with a 65% 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 285/65R20?
Yes, as long as the replacement keeps the overall diameter close to stock so the speedometer stays accurate. Common plus-size moves from 285/65R20 are 295/65R20, 295/60R21, 305/50R22.
Will 285/65R20 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.