275/70R18 vs 305/65R18
305/65R18 is a safe swap for 275/70R18 by the usual ±3% rule: the diameter differs by +1.37%.
Speedometer and odometer
With 305/65R18 on a car calibrated for 275/70R18, the speedometer reads 59.2 mph when you're really doing 60, and the odometer under-counts by 1.4%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.4 mph |
| 45 mph | 45.6 mph |
| 60 mph | 60.8 mph |
| 70 mph | 71.0 mph |
| 80 mph | 81.1 mph |
Other sizes close to 275/70R18
- 275/70R18 vs 275/65R18-3.27%
- 275/70R18 vs 265/65R18-4.81%
- 275/70R18 vs 265/70R18-1.66%
- 275/70R18 vs 255/70R18-3.32%
- 275/70R18 vs 285/65R18-1.72%
- 275/70R18 vs 295/70R18+3.32%
- 275/70R18 vs 295/70R17+0.31%
- 275/70R18 vs 33x12.50R18-0.47%
- 275/70R18 vs 33x12.50R17-0.47%
- 275/70R18 vs 325/65R18+4.45%
- 275/70R18 vs 305/70R18+4.99%
- 275/70R18 vs 255/80R17-0.28%
Questions
Can I replace 275/70R18 with 305/65R18?
305/65R18 is a safe swap for 275/70R18 by the usual ±3% rule: the diameter differs by +1.37%.
What's the difference between 275/70R18 and 305/65R18?
305/65R18 is 0.45" taller and 30 mm wider; the sidewall is +0.23". At an indicated 60 mph you'd actually be doing 60.8 mph.
Will 305/65R18 fit on 275/70R18 wheels?
Both use a 18" rim, so the wheel diameter matches; check the wheel's width range for a 305 mm tire and the fender clearance.