235/45R19 vs 315/30R20
315/30R20 is a safe swap for 235/45R19 by the usual ±3% rule: the diameter differs by +0.42%.
Speedometer and odometer
With 315/30R20 on a car calibrated for 235/45R19, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.2 mph |
| 60 mph | 60.3 mph |
| 70 mph | 70.3 mph |
| 80 mph | 80.3 mph |
Other sizes close to 235/45R19
- 235/45R19 vs 235/50R18-0.27%
- 235/45R19 vs 245/45R19+1.30%
- 235/45R19 vs 245/40R19-2.23%
- 235/45R19 vs 235/40R19-3.39%
- 235/45R19 vs 255/40R19-1.08%
- 235/45R19 vs 255/35R19-4.75%
- 235/45R19 vs 255/45R19+2.59%
- 235/45R19 vs 275/35R19-2.74%
- 235/45R19 vs 275/40R19+1.22%
- 235/45R19 vs 225/40R19-4.54%
- 235/45R19 vs 275/35R20+0.92%
- 235/45R19 vs 225/45R19-1.30%
Questions
Can I replace 235/45R19 with 315/30R20?
315/30R20 is a safe swap for 235/45R19 by the usual ±3% rule: the diameter differs by +0.42%.
What's the difference between 235/45R19 and 315/30R20?
315/30R20 is 0.11" taller and 80 mm wider; the sidewall is -0.44". At an indicated 60 mph you'd actually be doing 60.3 mph.
Will 315/30R20 fit on 235/45R19 wheels?
No — 235/45R19 needs a 19" wheel and 315/30R20 a 20" wheel. This is a plus/minus-size swap that changes wheels too.