285/70R18 vs 325/65R18
325/65R18 is a safe swap for 285/70R18 by the usual ±3% rule: the diameter differs by +2.74%.
Speedometer and odometer
With 325/65R18 on a car calibrated for 285/70R18, the speedometer reads 58.4 mph when you're really doing 60, and the odometer under-counts by 2.7%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.8 mph |
| 45 mph | 46.2 mph |
| 60 mph | 61.6 mph |
| 70 mph | 71.9 mph |
| 80 mph | 82.2 mph |
Other sizes close to 285/70R18
- 285/70R18 vs 275/65R18-4.85%
- 285/70R18 vs 275/70R18-1.64%
- 285/70R18 vs 265/70R18-3.27%
- 285/70R18 vs 255/70R18-4.91%
- 285/70R18 vs 35x12.50R18+3.83%
- 285/70R18 vs 285/65R18-3.33%
- 285/70R18 vs 295/70R18+1.64%
- 285/70R18 vs 33x12.50R18-2.10%
- 285/70R18 vs 285/75R17+0.36%
- 285/70R18 vs 285/75R18+3.33%
- 285/70R18 vs 305/70R18+3.27%
- 285/70R18 vs 305/65R18-0.29%
Questions
Can I replace 285/70R18 with 325/65R18?
325/65R18 is a safe swap for 285/70R18 by the usual ±3% rule: the diameter differs by +2.74%.
What's the difference between 285/70R18 and 325/65R18?
325/65R18 is 0.93" taller and 40 mm wider; the sidewall is +0.46". At an indicated 60 mph you'd actually be doing 61.6 mph.
Will 325/65R18 fit on 285/70R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 325 mm tire and the fender clearance.