Comparison
225/50 R17 vs 245/45 R18
Going from 225/50 R17 to 245/45 R18 steps up to a 18-inch rim while trimming sidewall to stay near OEM rolling diameter. This setup noticeably changes overall diameter compared to OEM. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement.
Indicated speed will drift far enough that recalibration is worth considering. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 245/45 R18 is 20.9 mm taller than 225/50 R17, shifting the speedometer by +3.18%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+20.9 mm
3.18%
Speedometer at 100
103.2 km/h
+3.18% error
Ground clearance
+10.5 mm
ride height delta
Sidewall change
-2.3 mm
revs/km: 469.7
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/compare/225-50-r17-vs-245-45-r18Detailed comparison
| Metric | 225/50 R17 | 245/45 R18 | Difference |
|---|---|---|---|
| Overall diameter | 656.8 mm | 677.7 mm | +20.9 mm (+3.18%) |
| Sidewall height | 112.5 mm | 110.3 mm | -2.3 mm |
| Circumference | 2.063 m | 2.129 m | +65.7 mm |
| Revs / km | 484.6 | 469.7 | -14.9 |
| Ground clearance | reference | +10.5 mm | +10.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.2 km/h | +3.18 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 103.2 km/h after switching to 245/45 R18 — a +3.18% 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 +10.5 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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225/50 R17
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245/45 R18
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