Comparison
225/55 R17 vs 225/55 R18
225/55 R18 is a plus-1 alternative to 225/55 R17 — the bigger wheel shows through a thinner sidewall. This alternative fitment noticeably changes overall diameter compared to OEM. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. Visually, the bigger wheel fills the arch and gives the car a more aggressive stance. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 225/55 R18 is 25.4 mm taller than 225/55 R17, shifting the speedometer by +3.74%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+25.4 mm
3.74%
Speedometer at 100
103.7 km/h
+3.74% error
Ground clearance
+12.7 mm
ride height delta
Sidewall change
0.0 mm
revs/km: 451.7
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/compare/225-55-r17-vs-225-55-r18Detailed comparison
| Metric | 225/55 R17 | 225/55 R18 | Difference |
|---|---|---|---|
| Overall diameter | 679.3 mm | 704.7 mm | +25.4 mm (+3.74%) |
| Sidewall height | 123.8 mm | 123.8 mm | 0.0 mm |
| Circumference | 2.134 m | 2.214 m | +79.8 mm |
| Revs / km | 468.6 | 451.7 | -16.9 |
| Ground clearance | reference | +12.7 mm | +12.7 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.7 km/h | +3.74 km/h |
Verdict: warning
Between 3% and 5% — noticeable speedometer drift; recalibration may be advisable.
Speedometer impact
At a true 100 km/h, your dashboard will read 103.7 km/h after switching to 225/55 R18 — a +3.74% offset. Use the speedometer error calculator to recheck for other indicated speeds, and the speedometer error guide for the full background.
Ground clearance change
The new tire's half-diameter changes ride height by +12.7 mm. Small differences are absorbed by suspension travel, but anything beyond ±10 mm can affect headlight aim, fender clearance and bump-stop margin. See the plus-sizing guide before committing.
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225/55 R17
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225/55 R18
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