215/55R17 vs 225/45R18 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 | 215/55R17 | 225/45R18 | Difference |
|---|---|---|---|
| Overall Diameter | 668.3 mm (26.3") | 659.7 mm (26") | -8.6 mm |
| Section Width | 215 mm (8.5") | 225 mm (8.9") | +10 mm |
| Sidewall Height | 118.3 mm | 101.3 mm | -17 mm |
| Circumference | 2099.5 mm | 2072.5 mm | -27 mm |
| Revolutions/Mile | 767 | 777 | +10 |
| Aspect Ratio | 55% | 45% | -10% |
| Rim Diameter | 17" | 18" | +1" |
Key Impact Summary
Speedometer Correction Table
When switching from 215/55R17 to 225/45R18, your speedometer will over-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 29.6 mph | -0.4 mph |
| 40 mph | 39.5 mph | -0.5 mph |
| 50 mph | 49.4 mph | -0.6 mph |
| 60 mph | 59.2 mph | -0.8 mph |
| 70 mph | 69.1 mph | -0.9 mph |
| 80 mph | 79 mph | -1 mph |
| 90 mph | 88.8 mph | -1.2 mph |
| 100 mph | 98.7 mph | -1.3 mph |
| 110 mph | 108.6 mph | -1.4 mph |
| 120 mph | 118.5 mph | -1.5 mph |
What This Swap Means
Wider tires (225/45R18): 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 17.0mm 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: Decreases by 4.3mm, lowering the center of gravity slightly which can improve handling stability.