245/40R18 vs 265/40R18
265/40R18 is a safe swap for 245/40R18 by the usual ±3% rule: the diameter differs by +2.45%.
Speedometer and odometer
With 265/40R18 on a car calibrated for 245/40R18, the speedometer reads 58.6 mph when you're really doing 60, and the odometer under-counts by 2.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.7 mph |
| 45 mph | 46.1 mph |
| 60 mph | 61.5 mph |
| 70 mph | 71.7 mph |
| 80 mph | 82.0 mph |
Other sizes close to 245/40R18
- 245/40R18 vs 225/45R18+1.00%
- 245/40R18 vs 225/40R18-2.45%
- 245/40R18 vs 225/50R17+0.55%
- 245/40R18 vs 245/45R18+3.75%
- 245/40R18 vs 235/45R18+2.37%
- 245/40R18 vs 235/40R18-1.22%
- 245/40R18 vs 225/50R18+4.44%
- 245/40R18 vs 215/50R17-0.98%
- 245/40R18 vs 245/45R17-0.14%
- 245/40R18 vs 255/35R18-2.68%
- 245/40R18 vs 255/40R18+1.22%
- 245/40R18 vs 245/35R19+0.14%
Questions
Can I replace 245/40R18 with 265/40R18?
265/40R18 is a safe swap for 245/40R18 by the usual ±3% rule: the diameter differs by +2.45%.
What's the difference between 245/40R18 and 265/40R18?
265/40R18 is 0.63" taller and 20 mm wider; the sidewall is +0.31". At an indicated 60 mph you'd actually be doing 61.5 mph.
Will 265/40R18 fit on 245/40R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 265 mm tire and the fender clearance.