295/30R18 vs 255/40R17
255/40R17 is a safe swap for 295/30R18 by the usual ±3% rule: the diameter differs by +0.25%.
Speedometer and odometer
With 255/40R17 on a car calibrated for 295/30R18, the speedometer reads 59.8 mph when you're really doing 60, and the odometer under-counts by 0.3%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.1 mph |
| 45 mph | 45.1 mph |
| 60 mph | 60.2 mph |
| 70 mph | 70.2 mph |
| 80 mph | 80.2 mph |
Other sizes close to 295/30R18
- 295/30R18 vs 225/45R17+0.02%
- 295/30R18 vs 245/40R18+3.00%
- 295/30R18 vs 225/45R18+4.02%
- 295/30R18 vs 225/40R18+0.47%
- 295/30R18 vs 205/50R17+0.41%
- 295/30R18 vs 235/40R18+1.73%
- 295/30R18 vs 255/35R18+0.24%
- 295/30R18 vs 255/40R18+4.26%
- 295/30R18 vs 275/35R18+2.44%
- 295/30R18 vs 265/35R18+1.34%
- 295/30R18 vs 215/45R18+2.60%
- 295/30R18 vs 245/35R18-0.87%
Questions
Can I replace 295/30R18 with 255/40R17?
255/40R17 is a safe swap for 295/30R18 by the usual ±3% rule: the diameter differs by +0.25%.
What's the difference between 295/30R18 and 255/40R17?
255/40R17 is 0.06" taller and 40 mm narrower; the sidewall is +0.53". At an indicated 60 mph you'd actually be doing 60.2 mph.
Will 255/40R17 fit on 295/30R18 wheels?
No — 295/30R18 needs a 18" wheel and 255/40R17 a 17" wheel. This is a plus/minus-size swap that changes wheels too.