285/30R20 vs 255/35R20
255/35R20 is a safe swap for 285/30R20 by the usual ±3% rule: the diameter differs by +1.10%.
Speedometer and odometer
With 255/35R20 on a car calibrated for 285/30R20, the speedometer reads 59.3 mph when you're really doing 60, and the odometer under-counts by 1.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.3 mph |
| 45 mph | 45.5 mph |
| 60 mph | 60.7 mph |
| 70 mph | 70.8 mph |
| 80 mph | 80.9 mph |
Other sizes close to 285/30R20
- 285/30R20 vs 245/40R19-0.06%
- 285/30R20 vs 245/40R20+3.68%
- 285/30R20 vs 275/35R19-0.57%
- 285/30R20 vs 245/35R20+0.07%
- 285/30R20 vs 275/35R20+3.17%
- 285/30R20 vs 255/40R20+4.86%
- 285/30R20 vs 225/45R19+0.90%
- 285/30R20 vs 285/35R19+0.46%
- 285/30R20 vs 285/35R20+4.20%
- 285/30R20 vs 275/30R20-0.88%
- 285/30R20 vs 265/35R20+2.14%
- 285/30R20 vs 235/35R20-0.96%
Questions
Can I replace 285/30R20 with 255/35R20?
255/35R20 is a safe swap for 285/30R20 by the usual ±3% rule: the diameter differs by +1.10%.
What's the difference between 285/30R20 and 255/35R20?
255/35R20 is 0.30" taller and 30 mm narrower; the sidewall is +0.15". At an indicated 60 mph you'd actually be doing 60.7 mph.
Will 255/35R20 fit on 285/30R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.