265/35R18 vs 255/40R18
255/40R18 is a safe swap for 265/35R18 by the usual ±3% rule: the diameter differs by +2.88%.
Speedometer and odometer
With 255/40R18 on a car calibrated for 265/35R18, the speedometer reads 58.3 mph when you're really doing 60, and the odometer under-counts by 2.9%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.9 mph |
| 45 mph | 46.3 mph |
| 60 mph | 61.7 mph |
| 70 mph | 72.0 mph |
| 80 mph | 82.3 mph |
Other sizes close to 265/35R18
- 265/35R18 vs 245/40R18+1.63%
- 265/35R18 vs 225/45R18+2.65%
- 265/35R18 vs 225/40R18-0.86%
- 265/35R18 vs 235/45R18+4.05%
- 265/35R18 vs 205/50R17-0.92%
- 265/35R18 vs 235/40R18+0.39%
- 265/35R18 vs 215/50R17+0.64%
- 265/35R18 vs 235/45R17+0.09%
- 265/35R18 vs 255/35R18-1.09%
- 265/35R18 vs 235/35R19+0.68%
- 265/35R18 vs 275/35R18+1.09%
- 265/35R18 vs 215/45R18+1.24%
Questions
Can I replace 265/35R18 with 255/40R18?
255/40R18 is a safe swap for 265/35R18 by the usual ±3% rule: the diameter differs by +2.88%.
What's the difference between 265/35R18 and 255/40R18?
255/40R18 is 0.73" taller and 10 mm narrower; the sidewall is +0.36". At an indicated 60 mph you'd actually be doing 61.7 mph.
Will 255/40R18 fit on 265/35R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 255 mm tire and the fender clearance.