275/30R20 vs 285/30R20
285/30R20 is a safe swap for 275/30R20 by the usual ±3% rule: the diameter differs by +0.89%.
Speedometer and odometer
With 285/30R20 on a car calibrated for 275/30R20, the speedometer reads 59.5 mph when you're really doing 60, and the odometer under-counts by 0.9%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.3 mph |
| 45 mph | 45.4 mph |
| 60 mph | 60.5 mph |
| 70 mph | 70.6 mph |
| 80 mph | 80.7 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 265/35R20+3.05%
- 275/30R20 vs 235/35R20-0.07%
- 275/30R20 vs 295/30R20+1.78%
- 275/30R20 vs 305/30R20+2.67%
Questions
Can I replace 275/30R20 with 285/30R20?
285/30R20 is a safe swap for 275/30R20 by the usual ±3% rule: the diameter differs by +0.89%.
What's the difference between 275/30R20 and 285/30R20?
285/30R20 is 0.24" taller and 10 mm wider; the sidewall is +0.12". At an indicated 60 mph you'd actually be doing 60.5 mph.
Will 285/30R20 fit on 275/30R20 wheels?
Both use a 20" rim, so the wheel diameter matches; check the wheel's width range for a 285 mm tire and the fender clearance.