Comparison
225/55 R17 vs 225/40 R18
Compared to 225/55 R17, 225/40 R18 is 42.1 mm shorter and changes the speedometer reading by -6.20%.
Current Tire
225/55R17
New Tire
225/40R18
225/55 R17
225/40 R18
Ground line · scaled comparison
Not Recommended
Over 5% — speedometer & ABS may misread
Diameter change
-42.1 mm
-6.20%
Speedometer at 100
93.8 km/h
-6.20% error
Ground clearance
-21.0 mm
ride height delta
Sidewall change
-33.8 mm
revs/km: 499.5
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/compare/225-55-r17-vs-225-40-r18Detailed comparison
| Metric | 225/55 R17 | 225/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 679.3 mm | 637.2 mm | -42.1 mm (-6.20%) |
| Sidewall height | 123.8 mm | 90.0 mm | -33.8 mm |
| Circumference | 2.134 m | 2.002 m | -132.3 mm |
| Revs / km | 468.6 | 499.5 | +31.0 |
| Ground clearance | reference | -21.0 mm | -21.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 93.8 km/h | -6.20 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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225/55 R17
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225/40 R18