235/65R18 vs 245/65R17Tire Size Comparison
The 1.6% diameter difference is within the accepted 3% tolerance.
Comparison Details
Speedometer Correction
When switching from 235/65R18 to 245/65R17, your speedometer will differ from actual speed.
| Speedometer | Actual Speed | Difference |
|---|---|---|
| 30 km/h | 29.5 km/h | -0.5 km/h |
| 40 km/h | 39.3 km/h | -0.7 km/h |
| 50 km/h | 49.2 km/h | -0.8 km/h |
| 60 km/h | 59.0 km/h | -1.0 km/h |
| 70 km/h | 68.9 km/h | -1.1 km/h |
| 80 km/h | 78.7 km/h | -1.3 km/h |
| 90 km/h | 88.5 km/h | -1.5 km/h |
| 100 km/h | 98.4 km/h | -1.6 km/h |
| 110 km/h | 108.2 km/h | -1.8 km/h |
| 120 km/h | 118.0 km/h | -2.0 km/h |
| 130 km/h | 127.9 km/h | -2.1 km/h |
Vehicles Using These Sizes
Vehicles with 235/65R18
Vehicles with 245/65R17
Individual Tire Size Details
Practical Guidance
Switching from 235/65R18 to 245/65R17 is within the industry-accepted 3% diameter tolerance. Your speedometer, ABS, and traction control should function normally. Note: these sizes require different rim diameters (18" vs 17"), so you will need different wheels.
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
Safe. The overall diameter differs by -1.63%, width changes by 10mm.
Speedometer error will be -1.63%. At an indicated 100 km/h, actual speed is about 98.4 km/h.
Ground clearance changes by -6.2mm per side.