Comparison
225/50 R18 vs 225/55 R18
Going from 225/50 R18 to 225/55 R18 raises the aspect ratio by 5 points on the same 18-inch wheel. This swap moves rolling diameter well outside the usual OEM tolerance. Indicated speed will drift far enough that recalibration is worth considering. Extra sidewall absorbs impacts more readily — a sensible bias for daily commuting and broken pavement. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeA comfort-leaning direction that's easier on wheels and suspension over rough surfaces.
Quick math: 225/55 R18 is 22.5 mm taller than 225/50 R18, shifting the speedometer by +3.30%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+22.5 mm
3.30%
Speedometer at 100
103.3 km/h
+3.30% error
Ground clearance
+11.3 mm
ride height delta
Sidewall change
+11.3 mm
revs/km: 451.7
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/compare/225-50-r18-vs-225-55-r18Detailed comparison
| Metric | 225/50 R18 | 225/55 R18 | Difference |
|---|---|---|---|
| Overall diameter | 682.2 mm | 704.7 mm | +22.5 mm (+3.30%) |
| Sidewall height | 112.5 mm | 123.8 mm | +11.3 mm |
| Circumference | 2.143 m | 2.214 m | +70.7 mm |
| Revs / km | 466.6 | 451.7 | -14.9 |
| Ground clearance | reference | +11.3 mm | +11.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.3 km/h | +3.30 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 103.3 km/h after switching to 225/55 R18 — a +3.30% 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 +11.3 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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225/50 R18
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225/55 R18
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