Comparison
205/50 R16 vs 225/40 R18
225/40 R18 is a plus-2 alternative to 205/50 R16 — the bigger wheel shows through a thinner sidewall. This alternative fitment swings rolling diameter far enough to feel on the road. Indicated speed will drift far enough that recalibration is worth considering. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 225/40 R18 is 25.8 mm taller than 205/50 R16, shifting the speedometer by +4.22%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+25.8 mm
4.22%
Speedometer at 100
104.2 km/h
+4.22% error
Ground clearance
+12.9 mm
ride height delta
Sidewall change
-12.5 mm
revs/km: 499.5
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/compare/205-50-r16-vs-225-40-r18Detailed comparison
| Metric | 205/50 R16 | 225/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 611.4 mm | 637.2 mm | +25.8 mm (+4.22%) |
| Sidewall height | 102.5 mm | 90.0 mm | -12.5 mm |
| Circumference | 1.921 m | 2.002 m | +81.1 mm |
| Revs / km | 520.6 | 499.5 | -21.1 |
| Ground clearance | reference | +12.9 mm | +12.9 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 104.2 km/h | +4.22 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 104.2 km/h after switching to 225/40 R18 — a +4.22% 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 +12.9 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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205/50 R16
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225/40 R18
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