Comparison
235/50 R18 vs 235/55 R18
Going from 235/50 R18 to 235/55 R18 raises the aspect ratio by 5 points on the same 18-inch wheel. This tire combination noticeably changes overall diameter compared to OEM.
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: 235/55 R18 is 23.5 mm taller than 235/50 R18, shifting the speedometer by +3.39%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+23.5 mm
3.39%
Speedometer at 100
103.4 km/h
+3.39% error
Ground clearance
+11.8 mm
ride height delta
Sidewall change
+11.8 mm
revs/km: 444.8
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/compare/235-50-r18-vs-235-55-r18Detailed comparison
| Metric | 235/50 R18 | 235/55 R18 | Difference |
|---|---|---|---|
| Overall diameter | 692.2 mm | 715.7 mm | +23.5 mm (+3.39%) |
| Sidewall height | 117.5 mm | 129.3 mm | +11.8 mm |
| Circumference | 2.175 m | 2.248 m | +73.8 mm |
| Revs / km | 459.9 | 444.8 | -15.1 |
| Ground clearance | reference | +11.8 mm | +11.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.4 km/h | +3.39 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 103.4 km/h after switching to 235/55 R18 — a +3.39% 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 +11.8 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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235/50 R18
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235/55 R18
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