235/30R20 vs 285/30R19
285/30R19 is a safe swap for 235/30R20 by the usual ±3% rule: the diameter differs by +0.71%.
Speedometer and odometer
With 285/30R19 on a car calibrated for 235/30R20, the speedometer reads 59.6 mph when you're really doing 60, and the odometer under-counts by 0.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.3 mph |
| 60 mph | 60.4 mph |
| 70 mph | 70.5 mph |
| 80 mph | 80.6 mph |
Other sizes close to 235/30R20
- 235/30R20 vs 245/35R20+4.70%
- 235/30R20 vs 245/35R19+0.79%
- 235/30R20 vs 235/35R19-0.29%
- 235/30R20 vs 285/30R20+4.62%
- 235/30R20 vs 275/30R20+3.70%
- 235/30R20 vs 235/35R20+3.62%
- 235/30R20 vs 275/30R19-0.22%
- 235/30R20 vs 245/30R20+0.92%
- 235/30R20 vs 265/30R20+2.77%
- 235/30R20 vs 255/30R20+1.85%
- 235/30R20 vs 225/35R20+2.54%
- 235/30R20 vs 335/25R20+4.08%
Questions
Can I replace 235/30R20 with 285/30R19?
285/30R19 is a safe swap for 235/30R20 by the usual ±3% rule: the diameter differs by +0.71%.
What's the difference between 235/30R20 and 285/30R19?
285/30R19 is 0.18" taller and 50 mm wider; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 60.4 mph.
Will 285/30R19 fit on 235/30R20 wheels?
No — 235/30R20 needs a 20" wheel and 285/30R19 a 19" wheel. This is a plus/minus-size swap that changes wheels too.