225/45R18 vs 305/30R19
305/30R19 is a safe swap for 225/45R18 by the usual ±3% rule: the diameter differs by +0.89%.
Speedometer and odometer
With 305/30R19 on a car calibrated for 225/45R18, 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 225/45R18
- 225/45R18 vs 245/40R18-0.99%
- 225/45R18 vs 225/40R18-3.41%
- 225/45R18 vs 225/50R17-0.44%
- 225/45R18 vs 245/45R18+2.73%
- 225/45R18 vs 235/50R18+4.93%
- 225/45R18 vs 235/45R18+1.36%
- 225/45R18 vs 235/40R18-2.20%
- 225/45R18 vs 225/50R18+3.41%
- 225/45R18 vs 255/35R19+0.21%
- 225/45R18 vs 255/35R18-3.64%
- 225/45R18 vs 255/40R18+0.23%
- 225/45R18 vs 245/35R19-0.85%
Questions
Can I replace 225/45R18 with 305/30R19?
305/30R19 is a safe swap for 225/45R18 by the usual ±3% rule: the diameter differs by +0.89%.
What's the difference between 225/45R18 and 305/30R19?
305/30R19 is 0.23" taller and 80 mm wider; the sidewall is -0.38". At an indicated 60 mph you'd actually be doing 60.5 mph.
Will 305/30R19 fit on 225/45R18 wheels?
No — 225/45R18 needs a 18" wheel and 305/30R19 a 19" wheel. This is a plus/minus-size swap that changes wheels too.