Comparison
225/55 R18 vs 235/50 R18
On the same 18-inch wheel, 235/50 R18 grows the section width by 10 mm versus 225/55 R18. This wheel and tire pairing moves rolling diameter a touch off the original spec. Expect a slight but noticeable shift in indicated speed compared to the original tires. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeUseful when extra dry grip and stance matter more than a small fuel-economy hit.
Quick math: 235/50 R18 is 12.5 mm shorter than 225/55 R18, shifting the speedometer by -1.77%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-12.5 mm
-1.77%
Speedometer at 100
98.2 km/h
-1.77% error
Ground clearance
-6.3 mm
ride height delta
Sidewall change
-6.3 mm
revs/km: 459.9
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/compare/225-55-r18-vs-235-50-r18Detailed comparison
| Metric | 225/55 R18 | 235/50 R18 | Difference |
|---|---|---|---|
| Overall diameter | 704.7 mm | 692.2 mm | -12.5 mm (-1.77%) |
| Sidewall height | 123.8 mm | 117.5 mm | -6.3 mm |
| Circumference | 2.214 m | 2.175 m | -39.3 mm |
| Revs / km | 451.7 | 459.9 | +8.2 |
| Ground clearance | reference | -6.3 mm | -6.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 98.2 km/h | -1.77 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 98.2 km/h after switching to 235/50 R18 — a -1.77% 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 -6.3 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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225/55 R18
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235/50 R18
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