255/65R18 vs 275/65R18 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 | 255/65R18 | 275/65R18 | Difference |
|---|---|---|---|
| Overall Diameter | 788.7 mm (31.1") | 814.7 mm (32.1") | +26 mm |
| Section Width | 255 mm (10") | 275 mm (10.8") | +20 mm |
| Sidewall Height | 165.8 mm | 178.8 mm | +13 mm |
| Circumference | 2477.8 mm | 2559.5 mm | +81.7 mm |
| Revolutions/Mile | 650 | 629 | -21 |
| Aspect Ratio | 65% | 65% | 0% |
| Rim Diameter | 18" | 18" | 0" |
Key Impact Summary
Speedometer Correction Table
When switching from 255/65R18 to 275/65R18, 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 | 41.3 mph | +1.3 mph |
| 50 mph | 51.6 mph | +1.6 mph |
| 60 mph | 62 mph | +2 mph |
| 70 mph | 72.3 mph | +2.3 mph |
| 80 mph | 82.6 mph | +2.6 mph |
| 90 mph | 93 mph | +3 mph |
| 100 mph | 103.3 mph | +3.3 mph |
| 110 mph | 113.6 mph | +3.6 mph |
| 120 mph | 124 mph | +4 mph |
What This Swap Means
Wider tires (275/65R18): 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 13.0mm 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 13mm, providing slightly better approach angles for off-road driving and speed bump clearance.