235/60R17 vs 235/55R18 Side-by-side tire size comparison with specs and compatibility
Compatibility
+0.27% 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 | 235/60R17 | 235/55R18 | Difference |
|---|---|---|---|
| Overall Diameter | 713.8 mm (28.1") | 715.7 mm (28.2") | +1.9 mm |
| Section Width | 235 mm (9.3") | 235 mm (9.3") | 0 mm |
| Sidewall Height | 141 mm | 129.3 mm | -11.7 mm |
| Circumference | 2242.5 mm | 2248.4 mm | +5.9 mm |
| Revolutions/Mile | 718 | 716 | -2 |
| Aspect Ratio | 60% | 55% | -5% |
| Rim Diameter | 17" | 18" | +1" |
Key Impact Summary
Ground Clearance
+1 mm
Speedometer Error
+0.27%
Width Change
0 mm
Sidewall Change
-11.7 mm
Speedometer Correction Table
When switching from 235/60R17 to 235/55R18, 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 | 50.1 mph | +0.1 mph |
| 60 mph | 60.2 mph | +0.2 mph |
| 70 mph | 70.2 mph | +0.2 mph |
| 80 mph | 80.2 mph | +0.2 mph |
| 90 mph | 90.2 mph | +0.2 mph |
| 100 mph | 100.3 mph | +0.3 mph |
| 110 mph | 110.3 mph | +0.3 mph |
| 120 mph | 120.3 mph | +0.3 mph |
What This Swap Means
Shorter sidewall: The 11.7mm decrease in sidewall height improves steering response and cornering precision. However, ride quality becomes firmer and the wheels are more vulnerable to pothole damage. This is a common trade-off when upsizing wheels (plus-sizing).
Ground clearance: Increases by 1mm, providing slightly better approach angles for off-road driving and speed bump clearance.
Vehicles Using 235/60R17
Vehicles Using 235/55R18
Related Comparisons
Individual Tire Specs
Frequently Asked Questions
Yes, this swap is generally safe. The diameter difference is +0.27% (+1.9mm). This is within the safe 3% threshold and should not significantly affect your speedometer, ABS, or traction control.
Switching from 235/60R17 to 235/55R18 creates a +0.27% 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 235/60R17 to 235/55R18 changes ground clearance by +1mm. The vehicle will sit 1mm higher. Ground clearance change equals half the overall diameter difference.