Comparison
225/40 R18 vs 225/50 R17
Switching from 225/40 R18 to 225/50 R17 steps down to a 17-inch wheel — a familiar move for winter and dedicated all-terrain sets. This sizing approach noticeably changes overall diameter compared to OEM. Indicated speed will drift far enough that recalibration is worth considering. More sidewall typically improves comfort and curb protection, especially on city streets. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 225/50 R17 is 19.6 mm taller than 225/40 R18, shifting the speedometer by +3.08%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+19.6 mm
3.08%
Speedometer at 100
103.1 km/h
+3.08% error
Ground clearance
+9.8 mm
ride height delta
Sidewall change
+22.5 mm
revs/km: 484.6
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/compare/225-40-r18-vs-225-50-r17Detailed comparison
| Metric | 225/40 R18 | 225/50 R17 | Difference |
|---|---|---|---|
| Overall diameter | 637.2 mm | 656.8 mm | +19.6 mm (+3.08%) |
| Sidewall height | 90.0 mm | 112.5 mm | +22.5 mm |
| Circumference | 2.002 m | 2.063 m | +61.6 mm |
| Revs / km | 499.5 | 484.6 | -14.9 |
| Ground clearance | reference | +9.8 mm | +9.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.1 km/h | +3.08 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 103.1 km/h after switching to 225/50 R17 — a +3.08% 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 +9.8 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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225/40 R18
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225/50 R17
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