245/35R18 vs 225/40R18
225/40R18 is a safe swap for 245/35R18 by the usual ±3% rule: the diameter differs by +1.35%.
Speedometer and odometer
With 225/40R18 on a car calibrated for 245/35R18, the speedometer reads 59.2 mph when you're really doing 60, and the odometer under-counts by 1.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.4 mph |
| 45 mph | 45.6 mph |
| 60 mph | 60.8 mph |
| 70 mph | 70.9 mph |
| 80 mph | 81.1 mph |
Other sizes close to 245/35R18
- 245/35R18 vs 225/45R17+0.89%
- 245/35R18 vs 245/40R18+3.90%
- 245/35R18 vs 225/45R18+4.93%
- 245/35R18 vs 215/45R17-0.54%
- 245/35R18 vs 235/40R18+2.62%
- 245/35R18 vs 255/35R18+1.11%
- 245/35R18 vs 245/40R17-0.14%
- 245/35R18 vs 275/35R18+3.34%
- 245/35R18 vs 265/35R18+2.23%
- 245/35R18 vs 215/45R18+3.50%
- 245/35R18 vs 215/40R18+0.08%
- 245/35R18 vs 285/35R18+4.45%
Questions
Can I replace 245/35R18 with 225/40R18?
225/40R18 is a safe swap for 245/35R18 by the usual ±3% rule: the diameter differs by +1.35%.
What's the difference between 245/35R18 and 225/40R18?
225/40R18 is 0.33" taller and 20 mm narrower; the sidewall is +0.17". At an indicated 60 mph you'd actually be doing 60.8 mph.
Will 225/40R18 fit on 245/35R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 225 mm tire and the fender clearance.