275/55R20 vs 285/55R20 Side-by-side tire size comparison with specs and compatibility
This tire swap is within the safe 3% diameter threshold. It should not cause issues with speedometer accuracy, ABS, or traction control systems.
Full Specifications Comparison
| Specification | 275/55R20 | 285/55R20 | Difference |
|---|---|---|---|
| Overall Diameter | 810.5 mm (31.9") | 821.5 mm (32.3") | +11 mm |
| Section Width | 275 mm (10.8") | 285 mm (11.2") | +10 mm |
| Sidewall Height | 151.3 mm | 156.8 mm | +5.5 mm |
| Circumference | 2546.3 mm | 2580.8 mm | +34.5 mm |
| Revolutions/Mile | 632 | 624 | -8 |
| Aspect Ratio | 55% | 55% | 0% |
| Rim Diameter | 20" | 20" | 0" |
Key Impact Summary
Speedometer Correction Table
When switching from 275/55R20 to 285/55R20, your speedometer will under-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 30.4 mph | +0.4 mph |
| 40 mph | 40.5 mph | +0.5 mph |
| 50 mph | 50.7 mph | +0.7 mph |
| 60 mph | 60.8 mph | +0.8 mph |
| 70 mph | 71 mph | +1 mph |
| 80 mph | 81.1 mph | +1.1 mph |
| 90 mph | 91.2 mph | +1.2 mph |
| 100 mph | 101.4 mph | +1.4 mph |
| 110 mph | 111.5 mph | +1.5 mph |
| 120 mph | 121.6 mph | +1.6 mph |
What This Swap Means
Wider tires (285/55R20): The 10mm wider contact patch provides better grip in dry conditions and improved cornering stability. However, wider tires increase rolling resistance slightly, which may affect fuel economy by 1-2%. They are also more susceptible to hydroplaning in wet conditions.
Taller sidewall: The 5.5mm increase in sidewall height provides a more comfortable ride by absorbing more road imperfections. Taller sidewalls also offer better protection against pothole damage to wheels. The trade-off is slightly less responsive steering feel.
Ground clearance: Increases by 5.5mm, providing slightly better approach angles for off-road driving and speed bump clearance.