235/40R18 vs 275/30R19
275/30R19 is a safe swap for 235/40R18 by the usual ±3% rule: the diameter differs by +0.37%.
Speedometer and odometer
With 275/30R19 on a car calibrated for 235/40R18, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.2 mph |
| 60 mph | 60.2 mph |
| 70 mph | 70.3 mph |
| 80 mph | 80.3 mph |
Other sizes close to 235/40R18
- 235/40R18 vs 245/40R18+1.24%
- 235/40R18 vs 225/45R18+2.25%
- 235/40R18 vs 225/40R18-1.24%
- 235/40R18 vs 235/45R18+3.64%
- 235/40R18 vs 215/50R17+0.25%
- 235/40R18 vs 235/45R17-0.29%
- 235/40R18 vs 255/35R18-1.47%
- 235/40R18 vs 255/40R18+2.48%
- 235/40R18 vs 235/35R19+0.29%
- 235/40R18 vs 275/35R18+0.70%
- 235/40R18 vs 265/35R18-0.39%
- 235/40R18 vs 275/40R18+4.96%
Questions
Can I replace 235/40R18 with 275/30R19?
275/30R19 is a safe swap for 235/40R18 by the usual ±3% rule: the diameter differs by +0.37%.
What's the difference between 235/40R18 and 275/30R19?
275/30R19 is 0.09" taller and 40 mm wider; the sidewall is -0.45". At an indicated 60 mph you'd actually be doing 60.2 mph.
Will 275/30R19 fit on 235/40R18 wheels?
No — 235/40R18 needs a 18" wheel and 275/30R19 a 19" wheel. This is a plus/minus-size swap that changes wheels too.