275/60R18 vs 305/60R18
305/60R18 is outside the ±3% rule as a replacement for 275/60R18: the diameter differs by +4.57%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 305/60R18 on a car calibrated for 275/60R18, the speedometer reads 57.4 mph when you're really doing 60, and the odometer under-counts by 4.6%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.4 mph |
| 45 mph | 47.1 mph |
| 60 mph | 62.7 mph |
| 70 mph | 73.2 mph |
| 80 mph | 83.7 mph |
Other sizes close to 275/60R18
- 275/60R18 vs 275/65R18+3.49%
- 275/60R18 vs 265/60R18-1.52%
- 275/60R18 vs 245/60R18-4.57%
- 275/60R18 vs 265/65R18+1.84%
- 275/60R18 vs 235/65R18-3.11%
- 275/60R18 vs 255/70R18+3.43%
- 275/60R18 vs 255/65R18+0.19%
- 275/60R18 vs 255/60R19+0.18%
- 275/60R18 vs 255/70R17+0.20%
- 275/60R18 vs 255/60R18-3.05%
- 275/60R18 vs 235/75R17-0.37%
- 275/60R18 vs 285/60R18+1.52%
Questions
Can I replace 275/60R18 with 305/60R18?
305/60R18 is outside the ±3% rule as a replacement for 275/60R18: the diameter differs by +4.57%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 275/60R18 and 305/60R18?
305/60R18 is 1.42" taller and 30 mm wider; the sidewall is +0.71". At an indicated 60 mph you'd actually be doing 62.7 mph.
Will 305/60R18 fit on 275/60R18 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.