275/35R18 vs 245/40R18
245/40R18 is a safe swap for 275/35R18 by the usual ±3% rule: the diameter differs by +0.54%.
Speedometer and odometer
With 245/40R18 on a car calibrated for 275/35R18, the speedometer reads 59.7 mph when you're really doing 60, and the odometer under-counts by 0.5%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.2 mph |
| 45 mph | 45.2 mph |
| 60 mph | 60.3 mph |
| 70 mph | 70.4 mph |
| 80 mph | 80.4 mph |
Other sizes close to 275/35R18
- 275/35R18 vs 225/45R18+1.54%
- 275/35R18 vs 225/40R18-1.92%
- 275/35R18 vs 245/45R18+4.31%
- 275/35R18 vs 235/45R18+2.92%
- 275/35R18 vs 235/40R18-0.69%
- 275/35R18 vs 215/50R17-0.45%
- 275/35R18 vs 235/45R17-0.99%
- 275/35R18 vs 245/45R17+0.40%
- 275/35R18 vs 255/35R18-2.15%
- 275/35R18 vs 255/40R18+1.77%
- 275/35R18 vs 245/35R19+0.68%
- 275/35R18 vs 235/35R19-0.40%
Questions
Can I replace 275/35R18 with 245/40R18?
245/40R18 is a safe swap for 275/35R18 by the usual ±3% rule: the diameter differs by +0.54%.
What's the difference between 275/35R18 and 245/40R18?
245/40R18 is 0.14" taller and 30 mm narrower; the sidewall is +0.07". At an indicated 60 mph you'd actually be doing 60.3 mph.
Will 245/40R18 fit on 275/35R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 245 mm tire and the fender clearance.