Comparison
215/50 R16 vs 235/40 R18
235/40 R18 is a plus-2 alternative to 215/50 R16 — the bigger wheel shows through a thinner sidewall. This swap noticeably changes overall diameter compared to OEM. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 235/40 R18 is 23.8 mm taller than 215/50 R16, shifting the speedometer by +3.83%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+23.8 mm
3.83%
Speedometer at 100
103.8 km/h
+3.83% error
Ground clearance
+11.9 mm
ride height delta
Sidewall change
-13.5 mm
revs/km: 493.4
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/compare/215-50-r16-vs-235-40-r18Detailed comparison
| Metric | 215/50 R16 | 235/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 621.4 mm | 645.2 mm | +23.8 mm (+3.83%) |
| Sidewall height | 107.5 mm | 94.0 mm | -13.5 mm |
| Circumference | 1.952 m | 2.027 m | +74.8 mm |
| Revs / km | 512.2 | 493.4 | -18.9 |
| Ground clearance | reference | +11.9 mm | +11.9 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.8 km/h | +3.83 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 103.8 km/h after switching to 235/40 R18 — a +3.83% 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 +11.9 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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215/50 R16
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235/40 R18
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