255/70R18 vs 275/70R18 Side-by-side tire size comparison with specs and compatibility
This tire swap is between 3-5% diameter difference. Check for fender clearance and be aware of speedometer error. May require recalibration.
Full Specifications Comparison
| Specification | 255/70R18 | 275/70R18 | Difference |
|---|---|---|---|
| Overall Diameter | 814.2 mm (32.1") | 842.2 mm (33.2") | +28 mm |
| Section Width | 255 mm (10") | 275 mm (10.8") | +20 mm |
| Sidewall Height | 178.5 mm | 192.5 mm | +14 mm |
| Circumference | 2557.9 mm | 2645.8 mm | +87.9 mm |
| Revolutions/Mile | 629 | 608 | -21 |
| Aspect Ratio | 70% | 70% | 0% |
| Rim Diameter | 18" | 18" | 0" |
Key Impact Summary
Speedometer Correction Table
When switching from 255/70R18 to 275/70R18, your speedometer will under-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 31 mph | +1 mph |
| 40 mph | 41.4 mph | +1.4 mph |
| 50 mph | 51.7 mph | +1.7 mph |
| 60 mph | 62.1 mph | +2.1 mph |
| 70 mph | 72.4 mph | +2.4 mph |
| 80 mph | 82.8 mph | +2.8 mph |
| 90 mph | 93.1 mph | +3.1 mph |
| 100 mph | 103.4 mph | +3.4 mph |
| 110 mph | 113.8 mph | +3.8 mph |
| 120 mph | 124.1 mph | +4.1 mph |
What This Swap Means
Wider tires (275/70R18): The 20mm 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 14.0mm 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 14mm, providing slightly better approach angles for off-road driving and speed bump clearance.