215/50R17 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 | 215/50R17 | 225/45R18 | Difference |
|---|---|---|---|
| Overall Diameter | 646.8 mm (25.5") | 659.7 mm (26") | +12.9 mm |
| Section Width | 215 mm (8.5") | 225 mm (8.9") | +10 mm |
| Sidewall Height | 107.5 mm | 101.3 mm | -6.2 mm |
| Circumference | 2032 mm | 2072.5 mm | +40.5 mm |
| Revolutions/Mile | 792 | 777 | -15 |
| Aspect Ratio | 50% | 45% | -5% |
| Rim Diameter | 17" | 18" | +1" |
Key Impact Summary
Speedometer Correction Table
When switching from 215/50R17 to 225/45R18, 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 (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 6.2mm 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 6.5mm, providing slightly better approach angles for off-road driving and speed bump clearance.