275/30R20 vs 305/30R20
305/30R20 is a safe swap for 275/30R20 by the usual ±3% rule: the diameter differs by +2.67%.
Speedometer and odometer
With 305/30R20 on a car calibrated for 275/30R20, 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 | 82.1 mph |
Other sizes close to 275/30R20
- 275/30R20 vs 245/40R19+0.83%
- 275/30R20 vs 235/40R19-0.36%
- 275/30R20 vs 245/40R20+4.61%
- 275/30R20 vs 275/35R19+0.31%
- 275/30R20 vs 245/35R20+0.97%
- 275/30R20 vs 255/35R20+2.01%
- 275/30R20 vs 275/35R20+4.09%
- 275/30R20 vs 265/35R19-0.73%
- 275/30R20 vs 285/30R20+0.89%
- 275/30R20 vs 265/35R20+3.05%
- 275/30R20 vs 235/35R20-0.07%
- 275/30R20 vs 295/30R20+1.78%
Questions
Can I replace 275/30R20 with 305/30R20?
305/30R20 is a safe swap for 275/30R20 by the usual ±3% rule: the diameter differs by +2.67%.
What's the difference between 275/30R20 and 305/30R20?
305/30R20 is 0.71" taller and 30 mm wider; the sidewall is +0.35". At an indicated 60 mph you'd actually be doing 61.6 mph.
Will 305/30R20 fit on 275/30R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 305 mm tire and the fender clearance.