275/50R20 vs 305/50R20
305/50R20 is outside the ±3% rule as a replacement for 275/50R20: the diameter differs by +3.83%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
Speedometer and odometer
With 305/50R20 on a car calibrated for 275/50R20, the speedometer reads 57.8 mph when you're really doing 60, and the odometer under-counts by 3.8%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 31.1 mph |
| 45 mph | 46.7 mph |
| 60 mph | 62.3 mph |
| 70 mph | 72.7 mph |
| 80 mph | 83.1 mph |
Other sizes close to 275/50R20
- 275/50R20 vs 275/55R20+3.51%
- 275/50R20 vs 255/50R20-2.55%
- 275/50R20 vs 265/50R20-1.28%
- 275/50R20 vs 245/50R20-3.83%
- 275/50R20 vs 275/45R20-3.51%
- 275/50R20 vs 255/55R20+0.70%
- 275/50R20 vs 235/55R20-2.11%
- 275/50R20 vs 265/45R20-4.66%
- 275/50R20 vs 255/60R19+0.72%
- 275/50R20 vs 285/55R20+4.92%
- 275/50R20 vs 275/45R21-0.27%
- 275/50R20 vs 295/40R20-4.98%
Questions
Can I replace 275/50R20 with 305/50R20?
305/50R20 is outside the ±3% rule as a replacement for 275/50R20: the diameter differs by +3.83%, so the speedometer, odometer and ABS calibration will be off and clearance needs checking.
What's the difference between 275/50R20 and 305/50R20?
305/50R20 is 1.18" taller and 30 mm wider; the sidewall is +0.59". At an indicated 60 mph you'd actually be doing 62.3 mph.
Will 305/50R20 fit on 275/50R20 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.