235/65R18 vs 245/65R17 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 | 235/65R18 | 245/65R17 | Difference |
|---|---|---|---|
| Overall Diameter | 762.7 mm (30") | 750.3 mm (29.5") | -12.4 mm |
| Section Width | 235 mm (9.3") | 245 mm (9.6") | +10 mm |
| Sidewall Height | 152.8 mm | 159.3 mm | +6.5 mm |
| Circumference | 2396.1 mm | 2357.1 mm | -39 mm |
| Revolutions/Mile | 672 | 683 | +11 |
| Aspect Ratio | 65% | 65% | 0% |
| Rim Diameter | 18" | 17" | -1" |
Key Impact Summary
Speedometer Correction Table
When switching from 235/65R18 to 245/65R17, your speedometer will over-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 29.5 mph | -0.5 mph |
| 40 mph | 39.3 mph | -0.7 mph |
| 50 mph | 49.2 mph | -0.8 mph |
| 60 mph | 59 mph | -1 mph |
| 70 mph | 68.9 mph | -1.1 mph |
| 80 mph | 78.7 mph | -1.3 mph |
| 90 mph | 88.5 mph | -1.5 mph |
| 100 mph | 98.4 mph | -1.6 mph |
| 110 mph | 108.2 mph | -1.8 mph |
| 120 mph | 118 mph | -2 mph |
What This Swap Means
Wider tires (245/65R17): 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.
Taller sidewall: The 6.5mm increase in sidewall height provides a more comfortable ride by absorbing more road imperfections. Taller sidewalls also offer better protection against pothole damage to wheels. The trade-off is slightly less responsive steering feel.
Ground clearance: Decreases by 6.2mm, lowering the center of gravity slightly which can improve handling stability.