235/45R18 vs 225/45R17Tire Size Comparison
The 5.1% diameter difference exceeds 5% and could affect ABS and traction control.
Comparison Details
Speedometer Correction
When switching from 235/45R18 to 225/45R17, your speedometer will differ from actual speed.
| Speedometer | Actual Speed | Difference |
|---|---|---|
| 30 km/h | 28.5 km/h | -1.5 km/h |
| 40 km/h | 37.9 km/h | -2.1 km/h |
| 50 km/h | 47.4 km/h | -2.6 km/h |
| 60 km/h | 56.9 km/h | -3.1 km/h |
| 70 km/h | 66.4 km/h | -3.6 km/h |
| 80 km/h | 75.9 km/h | -4.1 km/h |
| 90 km/h | 85.4 km/h | -4.6 km/h |
| 100 km/h | 94.9 km/h | -5.1 km/h |
| 110 km/h | 104.3 km/h | -5.7 km/h |
| 120 km/h | 113.8 km/h | -6.2 km/h |
| 130 km/h | 123.3 km/h | -6.7 km/h |
Vehicles Using These Sizes
Vehicles with 235/45R18
Vehicles with 225/45R17
Individual Tire Size Details
Practical Guidance
A 5.1% diameter difference is significantly outside the safe replacement range. Switching from 235/45R18 to 225/45R17 can cause dangerous speedometer inaccuracy, ABS/traction control malfunctions, and potential clearance issues. This change is not recommended without professional verification and possible ECU recalibration.
The 3% diameter tolerance is a widely accepted industry guideline referenced by the ETRTO and most vehicle manufacturers. When in doubt, consult your vehicle's owner's manual or a qualified tire professional. For U.S. tire safety standards and recalls, see the NHTSA Tire Safety page.
Frequently Asked Questions
Not Recommended. The overall diameter differs by -5.14%, width changes by -10mm.
Speedometer error will be -5.14%. At an indicated 100 km/h, actual speed is about 94.9 km/h.
Ground clearance changes by -17.2mm per side.