275/30R19 vs 245/40R18
245/40R18 is a safe swap for 275/30R19 by the usual ±3% rule: the diameter differs by +0.86%.
Speedometer and odometer
With 245/40R18 on a car calibrated for 275/30R19, 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 275/30R19
- 275/30R19 vs 245/40R19+4.79%
- 275/30R19 vs 235/40R18-0.37%
- 275/30R19 vs 235/40R19+3.55%
- 275/30R19 vs 255/35R19+2.08%
- 275/30R19 vs 275/35R19+4.25%
- 275/30R19 vs 245/35R19+1.00%
- 275/30R19 vs 225/40R19+2.32%
- 275/30R19 vs 235/35R19-0.08%
- 275/30R19 vs 275/35R18+0.32%
- 275/30R19 vs 265/35R18-0.76%
- 275/30R19 vs 265/35R19+3.17%
- 275/30R19 vs 215/45R18+0.48%
Questions
Can I replace 275/30R19 with 245/40R18?
245/40R18 is a safe swap for 275/30R19 by the usual ±3% rule: the diameter differs by +0.86%.
What's the difference between 275/30R19 and 245/40R18?
245/40R18 is 0.22" taller and 30 mm narrower; the sidewall is +0.61". At an indicated 60 mph you'd actually be doing 60.5 mph.
Will 245/40R18 fit on 275/30R19 wheels?
No — 275/30R19 needs a 19" wheel and 245/40R18 a 18" wheel. This is a plus/minus-size swap that changes wheels too.