275/30R20 vs 285/30R20 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 | 275/30R20 | 285/30R20 | Difference |
|---|---|---|---|
| Overall Diameter | 673 mm (26.5") | 679 mm (26.7") | +6 mm |
| Section Width | 275 mm (10.8") | 285 mm (11.2") | +10 mm |
| Sidewall Height | 82.5 mm | 85.5 mm | +3 mm |
| Circumference | 2114.3 mm | 2133.1 mm | +18.8 mm |
| Revolutions/Mile | 761 | 754 | -7 |
| Aspect Ratio | 30% | 30% | 0% |
| Rim Diameter | 20" | 20" | 0" |
Key Impact Summary
Speedometer Correction Table
When switching from 275/30R20 to 285/30R20, your speedometer will under-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 30.3 mph | +0.3 mph |
| 40 mph | 40.4 mph | +0.4 mph |
| 50 mph | 50.4 mph | +0.4 mph |
| 60 mph | 60.5 mph | +0.5 mph |
| 70 mph | 70.6 mph | +0.6 mph |
| 80 mph | 80.7 mph | +0.7 mph |
| 90 mph | 90.8 mph | +0.8 mph |
| 100 mph | 100.9 mph | +0.9 mph |
| 110 mph | 111 mph | +1 mph |
| 120 mph | 121.1 mph | +1.1 mph |
What This Swap Means
Wider tires (285/30R20): 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 3.0mm 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 3mm, providing slightly better approach angles for off-road driving and speed bump clearance.