225/55 R17 vs 235/50 R18
Compare the two sizes: total diameter, circumference, speedometer impact and how the car feels.
225/55 R17 → 235/50 R18
This swap stays within the safe ±3% window — the speedometer and ABS/ESP are essentially unaffected. Check brake and body clearance, and keep the load and speed indexes at or above the original.
225/55 R17 — original
235/50 R18 — new
What this swap means for your car
When you go from 225/55 R17 to 235/50 R18, the sidewall height changes from 123.8 mm to 117.5 mm. The shorter sidewall gives sharper turn-in and a firmer ride, with a bit more road noise.
The rim grows 225/55 R17″ → 235/50 R18″. The total diameter changes by +1.90%, which means the car sits slightly higher and the speedometer under-reads (you travel faster than the needle shows).
FAQ
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Use the free Tire Calculator to compare any two sizes, including custom ones.
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