225/40R19 vs 235/45R18
235/45R18 is a safe swap for 225/40R19 by the usual ±3% rule: the diameter differs by +0.92%.
Speedometer and odometer
With 235/45R18 on a car calibrated for 225/40R19, 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 | 60.6 mph |
| 70 mph | 70.6 mph |
| 80 mph | 80.7 mph |
Other sizes close to 225/40R19
- 225/40R19 vs 225/45R18-0.44%
- 225/40R19 vs 245/40R19+2.41%
- 225/40R19 vs 235/40R19+1.21%
- 225/40R19 vs 255/40R19+3.62%
- 225/40R19 vs 255/35R19-0.23%
- 225/40R19 vs 255/40R18-0.21%
- 225/40R19 vs 275/35R19+1.89%
- 225/40R19 vs 245/35R19-1.28%
- 225/40R19 vs 235/35R19-2.34%
- 225/40R19 vs 225/45R19+3.40%
- 225/40R19 vs 285/35R19+2.94%
- 225/40R19 vs 265/35R19+0.83%
Questions
Can I replace 225/40R19 with 235/45R18?
235/45R18 is a safe swap for 225/40R19 by the usual ±3% rule: the diameter differs by +0.92%.
What's the difference between 225/40R19 and 235/45R18?
235/45R18 is 0.24" taller and 10 mm wider; the sidewall is +0.62". At an indicated 60 mph you'd actually be doing 60.6 mph.
Will 235/45R18 fit on 225/40R19 wheels?
No — 225/40R19 needs a 19" wheel and 235/45R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.