Comparison
225/50 R17 vs 235/45 R18
Switching from 225/50 R17 to 235/45 R18 is a plus-1 upgrade that wraps a shorter sidewall around a larger 18-inch wheel. This sizing approach trims or stretches rolling diameter by a small margin.
The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. The wider section adds contact patch and lateral stability, while eating into fender and suspension clearance. Many drivers pick this direction primarily for appearance — the bigger rim simply looks more aggressive. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 235/45 R18 is 11.9 mm taller than 225/50 R17, shifting the speedometer by +1.81%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+11.9 mm
1.81%
Speedometer at 100
101.8 km/h
+1.81% error
Ground clearance
+6.0 mm
ride height delta
Sidewall change
-6.8 mm
revs/km: 476.0
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/compare/225-50-r17-vs-235-45-r18Detailed comparison
| Metric | 225/50 R17 | 235/45 R18 | Difference |
|---|---|---|---|
| Overall diameter | 656.8 mm | 668.7 mm | +11.9 mm (+1.81%) |
| Sidewall height | 112.5 mm | 105.8 mm | -6.8 mm |
| Circumference | 2.063 m | 2.101 m | +37.4 mm |
| Revs / km | 484.6 | 476.0 | -8.6 |
| Ground clearance | reference | +6.0 mm | +6.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.8 km/h | +1.81 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 101.8 km/h after switching to 235/45 R18 — a +1.81% 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 +6.0 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.
Back to
225/50 R17
Back to
235/45 R18
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