285/65R18 vs 275/70R18 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 | 285/65R18 | 275/70R18 | Difference |
|---|---|---|---|
| Overall Diameter | 827.7 mm (32.6") | 842.2 mm (33.2") | +14.5 mm |
| Section Width | 285 mm (11.2") | 275 mm (10.8") | -10 mm |
| Sidewall Height | 185.3 mm | 192.5 mm | +7.2 mm |
| Circumference | 2600.3 mm | 2645.8 mm | +45.5 mm |
| Revolutions/Mile | 619 | 608 | -11 |
| Aspect Ratio | 65% | 70% | +5% |
| Rim Diameter | 18" | 18" | 0" |
Key Impact Summary
Speedometer Correction Table
When switching from 285/65R18 to 275/70R18, your speedometer will under-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 30.5 mph | +0.5 mph |
| 40 mph | 40.7 mph | +0.7 mph |
| 50 mph | 50.9 mph | +0.9 mph |
| 60 mph | 61.1 mph | +1.1 mph |
| 70 mph | 71.2 mph | +1.2 mph |
| 80 mph | 81.4 mph | +1.4 mph |
| 90 mph | 91.6 mph | +1.6 mph |
| 100 mph | 101.8 mph | +1.8 mph |
| 110 mph | 111.9 mph | +1.9 mph |
| 120 mph | 122.1 mph | +2.1 mph |
What This Swap Means
Narrower tires (275/70R18): The 10mm narrower contact patch reduces rolling resistance, potentially improving fuel economy. Narrower tires also cut through standing water better, reducing hydroplaning risk. However, dry grip and cornering stability may decrease slightly.
Taller sidewall: The 7.2mm 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 7.3mm, providing slightly better approach angles for off-road driving and speed bump clearance.