Comparison
225/50 R18 vs 245/45 R17
Switching from 225/50 R18 to 245/45 R17 steps down to a 17-inch wheel — a familiar move for winter and dedicated all-terrain sets. This alternative fitment noticeably changes overall diameter compared to OEM. Indicated speed will drift far enough that recalibration is worth considering. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 245/45 R17 is 29.9 mm shorter than 225/50 R18, shifting the speedometer by -4.38%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-29.9 mm
-4.38%
Speedometer at 100
95.6 km/h
-4.38% error
Ground clearance
-15.0 mm
ride height delta
Sidewall change
-2.3 mm
revs/km: 488.0
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/compare/225-50-r18-vs-245-45-r17Detailed comparison
| Metric | 225/50 R18 | 245/45 R17 | Difference |
|---|---|---|---|
| Overall diameter | 682.2 mm | 652.3 mm | -29.9 mm (-4.38%) |
| Sidewall height | 112.5 mm | 110.3 mm | -2.3 mm |
| Circumference | 2.143 m | 2.049 m | -93.9 mm |
| Revs / km | 466.6 | 488.0 | +21.4 |
| Ground clearance | reference | -15.0 mm | -15.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 95.6 km/h | -4.38 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 95.6 km/h after switching to 245/45 R17 — a -4.38% 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 -15.0 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.
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225/50 R18
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245/45 R17
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