225/50R17 vs 235/50R18Tire Size Comparison
The 5.4% diameter difference exceeds 5% and could affect ABS and traction control.
Comparison Details
Speedometer Correction
When switching from 225/50R17 to 235/50R18, your speedometer will differ from actual speed.
| Speedometer | Actual Speed | Difference |
|---|---|---|
| 30 km/h | 31.6 km/h | +1.6 km/h |
| 40 km/h | 42.2 km/h | +2.2 km/h |
| 50 km/h | 52.7 km/h | +2.7 km/h |
| 60 km/h | 63.2 km/h | +3.2 km/h |
| 70 km/h | 73.8 km/h | +3.8 km/h |
| 80 km/h | 84.3 km/h | +4.3 km/h |
| 90 km/h | 94.9 km/h | +4.9 km/h |
| 100 km/h | 105.4 km/h | +5.4 km/h |
| 110 km/h | 115.9 km/h | +5.9 km/h |
| 120 km/h | 126.5 km/h | +6.5 km/h |
| 130 km/h | 137.0 km/h | +7.0 km/h |
Vehicles Using These Sizes
Vehicles with 225/50R17
Vehicles with 235/50R18
Individual Tire Size Details
Practical Guidance
A 5.4% diameter difference is significantly outside the safe replacement range. Switching from 225/50R17 to 235/50R18 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 5.39%, width changes by 10mm.
Speedometer error will be 5.39%. At an indicated 100 km/h, actual speed is about 105.4 km/h.
Ground clearance changes by +17.7mm per side.