295/30R18 vs 235/40R18
235/40R18 is a safe swap for 295/30R18 by the usual ±3% rule: the diameter differs by +1.73%.
Speedometer and odometer
With 235/40R18 on a car calibrated for 295/30R18, the speedometer reads 59.0 mph when you're really doing 60, and the odometer under-counts by 1.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.5 mph |
| 45 mph | 45.8 mph |
| 60 mph | 61.0 mph |
| 70 mph | 71.2 mph |
| 80 mph | 81.4 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 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 255/40R17+0.25%
- 295/30R18 vs 215/45R18+2.60%
- 295/30R18 vs 245/35R18-0.87%
Questions
Can I replace 295/30R18 with 235/40R18?
235/40R18 is a safe swap for 295/30R18 by the usual ±3% rule: the diameter differs by +1.73%.
What's the difference between 295/30R18 and 235/40R18?
235/40R18 is 0.43" taller and 60 mm narrower; the sidewall is +0.22". At an indicated 60 mph you'd actually be doing 61.0 mph.
Will 235/40R18 fit on 295/30R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 235 mm tire and the fender clearance.