Comparison
215/55 R17 vs 235/50 R18
Going from 215/55 R17 to 235/50 R18 steps up to a 18-inch rim while trimming sidewall to stay near OEM rolling diameter. This wheel and tire pairing moves rolling diameter well outside the usual OEM tolerance. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input.
Indicated speed will drift far enough that recalibration is worth considering. 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: 235/50 R18 is 23.9 mm taller than 215/55 R17, shifting the speedometer by +3.58%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+23.9 mm
3.58%
Speedometer at 100
103.6 km/h
+3.58% error
Ground clearance
+12.0 mm
ride height delta
Sidewall change
-0.8 mm
revs/km: 459.9
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/compare/215-55-r17-vs-235-50-r18Detailed comparison
| Metric | 215/55 R17 | 235/50 R18 | Difference |
|---|---|---|---|
| Overall diameter | 668.3 mm | 692.2 mm | +23.9 mm (+3.58%) |
| Sidewall height | 118.3 mm | 117.5 mm | -0.8 mm |
| Circumference | 2.100 m | 2.175 m | +75.1 mm |
| Revs / km | 476.3 | 459.9 | -16.4 |
| Ground clearance | reference | +12.0 mm | +12.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.6 km/h | +3.58 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 103.6 km/h after switching to 235/50 R18 — a +3.58% 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 +12.0 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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215/55 R17
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235/50 R18
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