245/45R18 vs 245/40R19
245/40R19 is a safe swap for 245/45R18 by the usual ±3% rule: the diameter differs by +0.13%.
Speedometer and odometer
With 245/40R19 on a car calibrated for 245/45R18, 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 245/45R18
- 245/45R18 vs 225/45R18-2.66%
- 245/45R18 vs 245/40R18-3.62%
- 245/45R18 vs 225/55R17+0.24%
- 245/45R18 vs 235/50R18+2.14%
- 245/45R18 vs 235/45R18-1.33%
- 245/45R18 vs 235/40R18-4.80%
- 245/45R18 vs 225/50R18+0.66%
- 245/45R18 vs 225/55R18+3.98%
- 245/45R18 vs 255/40R18-2.43%
- 245/45R18 vs 275/35R19-0.38%
- 245/45R18 vs 245/50R18+3.62%
- 245/45R18 vs 275/35R18-4.13%
Questions
Can I replace 245/45R18 with 245/40R19?
245/40R19 is a safe swap for 245/45R18 by the usual ±3% rule: the diameter differs by +0.13%.
What's the difference between 245/45R18 and 245/40R19?
245/40R19 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 245/40R19 fit on 245/45R18 wheels?
No — 245/45R18 needs a 18" wheel and 245/40R19 a 19" wheel. This is a plus/minus-size swap that changes wheels too.