255/35R18 vs 255/40R17
255/40R17 is a safe swap for 255/35R18 by the usual ±3% rule: the diameter differs by +0.02%.
Speedometer and odometer
With 255/40R17 on a car calibrated for 255/35R18, the speedometer reads 60.0 mph when you're really doing 60, and the odometer under-counts by 0.0%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.0 mph |
| 45 mph | 45.0 mph |
| 60 mph | 60.0 mph |
| 70 mph | 70.0 mph |
| 80 mph | 80.0 mph |
Other sizes close to 255/35R18
- 255/35R18 vs 225/45R17-0.22%
- 255/35R18 vs 245/40R18+2.75%
- 255/35R18 vs 225/45R18+3.78%
- 255/35R18 vs 225/40R18+0.24%
- 255/35R18 vs 205/50R17+0.17%
- 255/35R18 vs 235/40R18+1.49%
- 255/35R18 vs 255/40R18+4.01%
- 255/35R18 vs 275/35R18+2.20%
- 255/35R18 vs 265/35R18+1.10%
- 255/35R18 vs 215/45R18+2.36%
- 255/35R18 vs 245/35R18-1.10%
- 255/35R18 vs 225/35R19+0.69%
Questions
Can I replace 255/35R18 with 255/40R17?
255/40R17 is a safe swap for 255/35R18 by the usual ±3% rule: the diameter differs by +0.02%.
What's the difference between 255/35R18 and 255/40R17?
255/40R17 is 0.00" taller and 0 mm wider; the sidewall is +0.50". At an indicated 60 mph you'd actually be doing 60.0 mph.
Will 255/40R17 fit on 255/35R18 wheels?
No — 255/35R18 needs a 18" wheel and 255/40R17 a 17" wheel. This is a plus/minus-size swap that changes wheels too.