245/30R20 vs 255/35R20
255/35R20 is outside the ±3% rule as a replacement for 245/30R20: the diameter differs by +4.81%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 255/35R20 on a car calibrated for 245/30R20, the speedometer reads 57.2 mph when you're really doing 60, and the odometer under-counts by 4.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.4 mph |
| 45 mph | 47.2 mph |
| 60 mph | 62.9 mph |
| 70 mph | 73.4 mph |
| 80 mph | 83.8 mph |
Other sizes close to 245/30R20
- 245/30R20 vs 255/35R19+0.93%
- 245/30R20 vs 245/35R20+3.74%
- 245/30R20 vs 245/35R19-0.14%
- 245/30R20 vs 285/30R20+3.66%
- 245/30R20 vs 275/30R20+2.75%
- 245/30R20 vs 285/30R19-0.21%
- 245/30R20 vs 235/35R20+2.67%
- 245/30R20 vs 295/30R20+4.58%
- 245/30R20 vs 295/30R19+0.70%
- 245/30R20 vs 265/30R20+1.83%
- 245/30R20 vs 255/30R20+0.92%
- 245/30R20 vs 225/35R20+1.60%
Questions
Can I replace 245/30R20 with 255/35R20?
255/35R20 is outside the ±3% rule as a replacement for 245/30R20: the diameter differs by +4.81%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 245/30R20 and 255/35R20?
255/35R20 is 1.24" taller and 10 mm wider; the sidewall is +0.62". At an indicated 60 mph you'd actually be doing 62.9 mph.
Will 255/35R20 fit on 245/30R20 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.