225/40R18 vs 285/35R18
285/35R18 is outside the ±3% rule as a replacement for 225/40R18: the diameter differs by +3.06%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 285/35R18 on a car calibrated for 225/40R18, the speedometer reads 58.2 mph when you're really doing 60, and the odometer under-counts by 3.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.9 mph |
| 45 mph | 46.4 mph |
| 60 mph | 61.8 mph |
| 70 mph | 72.1 mph |
| 80 mph | 82.4 mph |
Other sizes close to 225/40R18
- 225/40R18 vs 225/45R17-0.46%
- 225/40R18 vs 245/40R18+2.51%
- 225/40R18 vs 225/45R18+3.53%
- 225/40R18 vs 235/45R18+4.94%
- 225/40R18 vs 205/50R17-0.06%
- 225/40R18 vs 235/40R18+1.26%
- 225/40R18 vs 235/45R17+0.96%
- 225/40R18 vs 255/35R18-0.24%
- 225/40R18 vs 255/40R18+3.77%
- 225/40R18 vs 275/35R18+1.96%
- 225/40R18 vs 265/35R18+0.86%
- 225/40R18 vs 255/40R17-0.22%
Questions
Can I replace 225/40R18 with 285/35R18?
285/35R18 is outside the ±3% rule as a replacement for 225/40R18: the diameter differs by +3.06%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 225/40R18 and 285/35R18?
285/35R18 is 0.77" taller and 60 mm wider; the sidewall is +0.38". At an indicated 60 mph you'd actually be doing 61.8 mph.
Will 285/35R18 fit on 225/40R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 285 mm tire and the fender clearance.