Comparison
225/50 R16 vs 235/40 R18
Plus-sizing from 225/50 R16 to 235/40 R18 keeps overall diameter close to factory while opening room for a larger 18-inch wheel. This swap moves rolling diameter a touch off the original spec.
Expect a slight but noticeable shift in indicated speed compared to the original tires. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. Visually, the bigger wheel fills the arch and gives the car a more aggressive stance. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 235/40 R18 is 13.8 mm taller than 225/50 R16, shifting the speedometer by +2.19%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+13.8 mm
2.19%
Speedometer at 100
102.2 km/h
+2.19% error
Ground clearance
+6.9 mm
ride height delta
Sidewall change
-18.5 mm
revs/km: 493.4
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/compare/225-50-r16-vs-235-40-r18Detailed comparison
| Metric | 225/50 R16 | 235/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 631.4 mm | 645.2 mm | +13.8 mm (+2.19%) |
| Sidewall height | 112.5 mm | 94.0 mm | -18.5 mm |
| Circumference | 1.984 m | 2.027 m | +43.4 mm |
| Revs / km | 504.1 | 493.4 | -10.8 |
| Ground clearance | reference | +6.9 mm | +6.9 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.2 km/h | +2.19 km/h |
Verdict: excellent
Within ±3% — speedometer, ABS and traction control should behave normally.
Speedometer impact
At a true 100 km/h, your dashboard will read 102.2 km/h after switching to 235/40 R18 — a +2.19% 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 +6.9 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.
Back to
225/50 R16
Back to
235/40 R18
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