275/45R20 vs 285/45R20 at a glance
| Measure | 275/45R20 (current) | 285/45R20 (new) | Difference |
|---|---|---|---|
| Overall height | 29.74 in | 30.10 in | +0.35 in (+1.19%) |
| Width | 10.83 in (275 mm) | 11.22 in (285 mm) | +10 mm |
| Sidewall | 4.87 in | 5.05 in | +0.18 in |
| Wheel | 20 in | 20 in | +0 in |
| Circumference | 93.4 in | 94.6 in | +1.1 in |
| Revs per mile | 678.1 | 670.1 | −8.0 |
Verdict: close match
Within the 3% rule of thumb, so the speedometer, gearing and ride height change little. Going from 275/45R20 to 285/45R20 is a 1.2% increase in overall height (+0.35 in), and the vehicle sits about 0.18 in higher. The tire is 10 mm wider. The 3% rule of thumb comes from Discount Tire and 1010tires; it is not a guarantee of fit.
True speed and odometer
| Speedometer shows | You are really doing | Difference |
|---|---|---|
| 35 mph | 35.4 mph | +0.4 mph |
| 45 mph | 45.5 mph | +0.5 mph |
| 55 mph | 55.7 mph | +0.7 mph |
| 60 mph | 60.7 mph | +0.7 mph |
| 65 mph | 65.8 mph | +0.8 mph |
| 70 mph | 70.8 mph | +0.8 mph |
| 75 mph | 75.9 mph | +0.9 mph |
Odometer: 1,000 indicated miles is 1,012 real miles, and 10,000 is 10,119.
The math
275/45R20: 20 + 2 × (275 × 45% ÷ 25.4) = 29.74 in. 285/45R20: 20 + 2 × (285 × 45% ÷ 25.4) = 30.10 in. Change = 30.10 ÷ 29.74 − 1 = +1.19%. True speed at 60 = 60 × 30.10 ÷ 29.74 = 60.71 mph.
Check next
- Regear and RPM at cruise for this swap
- Speedometer and odometer correction
- Other sizes within ±3% of 275/45R20
Calculated from the size alone. Real tires vary a little by brand and model, and the loaded radius is a bit smaller. Confirm the wheel width range, clearance, load index and speed rating for your vehicle. See how to read a tire size, the load index chart and the speed rating chart.
Size pages: 275/45R20 · 285/45R20. More swaps: all tire size comparisons.