285/65R18 vs 285/70R17 Side-by-side tire size comparison with specs and compatibility
Compatibility
+0.37% diameter difference
✓ Safe Swap
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 | 285/65R18 | 285/70R17 | Difference |
|---|---|---|---|
| Overall Diameter | 827.7 mm (32.6") | 830.8 mm (32.7") | +3.1 mm |
| Section Width | 285 mm (11.2") | 285 mm (11.2") | 0 mm |
| Sidewall Height | 185.3 mm | 199.5 mm | +14.2 mm |
| Circumference | 2600.3 mm | 2610 mm | +9.7 mm |
| Revolutions/Mile | 619 | 617 | -2 |
| Aspect Ratio | 65% | 70% | +5% |
| Rim Diameter | 18" | 17" | -1" |
Key Impact Summary
Ground Clearance
+1.5 mm
Speedometer Error
+0.37%
Width Change
0 mm
Sidewall Change
+14.2 mm
Speedometer Correction Table
When switching from 285/65R18 to 285/70R17, your speedometer will under-read. Here is the correction at common speeds:
| Speedometer Shows | Actual Speed (mph) | Difference |
|---|---|---|
| 30 mph | 30.1 mph | +0.1 mph |
| 40 mph | 40.1 mph | +0.1 mph |
| 50 mph | 50.2 mph | +0.2 mph |
| 60 mph | 60.2 mph | +0.2 mph |
| 70 mph | 70.3 mph | +0.3 mph |
| 80 mph | 80.3 mph | +0.3 mph |
| 90 mph | 90.3 mph | +0.3 mph |
| 100 mph | 100.4 mph | +0.4 mph |
| 110 mph | 110.4 mph | +0.4 mph |
| 120 mph | 120.4 mph | +0.4 mph |
What This Swap Means
Taller sidewall: The 14.2mm 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: Increases by 1.5mm, providing slightly better approach angles for off-road driving and speed bump clearance.
Vehicles Using 285/70R17
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Individual Tire Specs
Frequently Asked Questions
Yes, this swap is generally safe. The diameter difference is +0.37% (+3.1mm). This is within the safe 3% threshold and should not significantly affect your speedometer, ABS, or traction control.
Switching from 285/65R18 to 285/70R17 creates a +0.37% speedometer error. Your actual speed will be faster than displayed — at an indicated 60 mph, you'll actually be going 60.2 mph.
Switching from 285/65R18 to 285/70R17 changes ground clearance by +1.5mm. The vehicle will sit 1.5mm higher. Ground clearance change equals half the overall diameter difference.