245/45R19 vs 245/40R20
245/40R20 is a safe swap for 245/45R19 by the usual ±3% rule: the diameter differs by +0.13%.
Speedometer and odometer
With 245/40R20 on a car calibrated for 245/45R19, the speedometer reads 59.9 mph when you're really doing 60, and the odometer under-counts by 0.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.0 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.1 mph |
| 70 mph | 70.1 mph |
| 80 mph | 80.1 mph |
Other sizes close to 245/45R19
- 245/45R19 vs 245/40R19-3.48%
- 245/45R19 vs 255/50R19+4.91%
- 245/45R19 vs 235/40R19-4.62%
- 245/45R19 vs 255/40R19-2.35%
- 245/45R19 vs 225/55R18+0.23%
- 245/45R19 vs 255/45R19+1.28%
- 245/45R19 vs 275/35R19-3.98%
- 245/45R19 vs 225/55R19+3.84%
- 245/45R19 vs 275/40R19-0.07%
- 245/45R19 vs 275/35R20-0.37%
- 245/45R19 vs 225/45R19-2.56%
- 245/45R19 vs 245/50R18-0.13%
Questions
Can I replace 245/45R19 with 245/40R20?
245/40R20 is a safe swap for 245/45R19 by the usual ±3% rule: the diameter differs by +0.13%.
What's the difference between 245/45R19 and 245/40R20?
245/40R20 is 0.04" taller and 0 mm wider; the sidewall is -0.48". At an indicated 60 mph you'd actually be doing 60.1 mph.
Will 245/40R20 fit on 245/45R19 wheels?
No — 245/45R19 needs a 19" wheel and 245/40R20 a 20" wheel. This is a plus/minus-size swap that changes wheels too.