225/60R17 vs 235/55R18 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 | 225/60R17 | 235/55R18 | Difference |
|---|---|---|---|
| Overall Diameter | 701.8 mm (27.6") | 715.7 mm (28.2") | +13.9 mm |
| Section Width | 225 mm (8.9") | 235 mm (9.3") | +10 mm |
| Sidewall Height | 135 mm | 129.3 mm | -5.7 mm |
| Circumference | 2204.8 mm | 2248.4 mm | +43.6 mm |
| Revolutions/Mile | 730 | 716 | -14 |
| Aspect Ratio | 60% | 55% | -5% |
| Rim Diameter | 17" | 18" | +1" |
Key Impact Summary
Speedometer Correction Table
When switching from 225/60R17 to 235/55R18, your speedometer will under-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 30.6 mph | +0.6 mph |
| 40 mph | 40.8 mph | +0.8 mph |
| 50 mph | 51 mph | +1 mph |
| 60 mph | 61.2 mph | +1.2 mph |
| 70 mph | 71.4 mph | +1.4 mph |
| 80 mph | 81.6 mph | +1.6 mph |
| 90 mph | 91.8 mph | +1.8 mph |
| 100 mph | 102 mph | +2 mph |
| 110 mph | 112.2 mph | +2.2 mph |
| 120 mph | 122.4 mph | +2.4 mph |
What This Swap Means
Wider tires (235/55R18): 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.
Shorter sidewall: The 5.7mm decrease in sidewall height improves steering response and cornering precision. However, ride quality becomes firmer and the wheels are more vulnerable to pothole damage. This is a common trade-off when upsizing wheels (plus-sizing).
Ground clearance: Increases by 7mm, providing slightly better approach angles for off-road driving and speed bump clearance.