325/65R18 vs 35x12.50R18
35x12.50R18 is a safe swap for 325/65R18 by the usual ±3% rule: the diameter differs by +1.06%.
Side by side
| 325/65R18 | 35x12.50R18 | Difference | |
|---|---|---|---|
| Overall diameter | 34.63" | 35.00" | +0.37" (+1.06%) |
| Section width | 325 mm | 318 mm | -7 mm |
| Sidewall | 8.32" | 8.50" | +0.18" |
| Rim | 18" | 18" | same |
| Circumference | 108.8" | 110.0" | +1.2" |
| Revs per mile | 582 | 576 | -6 |
| Ride height | — | — | +0.18" |
| Speedometer reads 60 mph | 60.0 | 60.6 | +0.6 mph |
Speedometer and odometer
With 35x12.50R18 on a car calibrated for 325/65R18, the speedometer reads 59.4 mph when you're really doing 60, and the odometer under-counts by 1.1%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.3 mph |
| 45 mph | 45.5 mph |
| 60 mph | 60.6 mph |
| 70 mph | 70.7 mph |
| 80 mph | 80.8 mph |
Other sizes close to 325/65R18
Questions
Can I replace 325/65R18 with 35x12.50R18?
35x12.50R18 is a safe swap for 325/65R18 by the usual ±3% rule: the diameter differs by +1.06%.
What's the difference between 325/65R18 and 35x12.50R18?
35x12.50R18 is 0.37" taller and 7 mm narrower; the sidewall is +0.18". At an indicated 60 mph you'd actually be doing 60.6 mph.
Will 35x12.50R18 fit on 325/65R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 318 mm tire and the fender clearance.