Comparison
235/55 R17 vs 215/40 R18
Compared to 235/55 R17, 215/40 R18 is 61.1 mm shorter and changes the speedometer reading by -8.85%.
Current Tire
235/55R17
New Tire
215/40R18
235/55 R17
215/40 R18
Ground line · scaled comparison
Not Recommended
Over 5% — speedometer & ABS may misread
Diameter change
-61.1 mm
-8.85%
Speedometer at 100
91.1 km/h
-8.85% error
Ground clearance
-30.5 mm
ride height delta
Sidewall change
-43.3 mm
revs/km: 505.9
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/compare/235-55-r17-vs-215-40-r18Detailed comparison
| Metric | 235/55 R17 | 215/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 690.3 mm | 629.2 mm | -61.1 mm (-8.85%) |
| Sidewall height | 129.3 mm | 86.0 mm | -43.3 mm |
| Circumference | 2.169 m | 1.977 m | -192.0 mm |
| Revs / km | 461.1 | 505.9 | +44.8 |
| Ground clearance | reference | -30.5 mm | -30.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 91.1 km/h | -8.85 km/h |
Verdict: danger
Over 5% diameter difference — likely to affect speedometer accuracy, ABS calibration and gearing. Not recommended without professional review.
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235/55 R17
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215/40 R18