315/30R19 vs 245/45R18
245/45R18 is a safe swap for 315/30R19 by the usual ±3% rule: the diameter differs by +0.91%.
Speedometer and odometer
With 245/45R18 on a car calibrated for 315/30R19, the speedometer reads 59.5 mph when you're really doing 60, and the odometer under-counts by 0.9%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.3 mph |
| 45 mph | 45.4 mph |
| 60 mph | 60.5 mph |
| 70 mph | 70.6 mph |
| 80 mph | 80.7 mph |
Other sizes close to 315/30R19
- 315/30R19 vs 235/45R18-0.43%
- 315/30R19 vs 245/45R19+4.69%
- 315/30R19 vs 245/40R19+1.04%
- 315/30R19 vs 235/40R19-0.15%
- 315/30R19 vs 255/40R19+2.23%
- 315/30R19 vs 255/35R19-1.56%
- 315/30R19 vs 275/35R19+0.52%
- 315/30R19 vs 275/40R19+4.62%
- 315/30R19 vs 245/35R19-2.61%
- 315/30R19 vs 225/40R19-1.34%
- 315/30R19 vs 235/35R19-3.65%
- 315/30R19 vs 225/45R19+2.01%
Questions
Can I replace 315/30R19 with 245/45R18?
245/45R18 is a safe swap for 315/30R19 by the usual ±3% rule: the diameter differs by +0.91%.
What's the difference between 315/30R19 and 245/45R18?
245/45R18 is 0.24" taller and 70 mm narrower; the sidewall is +0.62". At an indicated 60 mph you'd actually be doing 60.5 mph.
Will 245/45R18 fit on 315/30R19 wheels?
No — 315/30R19 needs a 19" wheel and 245/45R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.