Comparison
225/50 R16 vs 245/40 R18
Plus-sizing from 225/50 R16 to 245/40 R18 keeps overall diameter close to factory while opening room for a larger 18-inch wheel. This sizing approach moves rolling diameter well outside the usual OEM tolerance. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement.
The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 245/40 R18 is 21.8 mm taller than 225/50 R16, shifting the speedometer by +3.45%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+21.8 mm
3.45%
Speedometer at 100
103.5 km/h
+3.45% error
Ground clearance
+10.9 mm
ride height delta
Sidewall change
-14.5 mm
revs/km: 487.3
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/compare/225-50-r16-vs-245-40-r18Detailed comparison
| Metric | 225/50 R16 | 245/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 631.4 mm | 653.2 mm | +21.8 mm (+3.45%) |
| Sidewall height | 112.5 mm | 98.0 mm | -14.5 mm |
| Circumference | 1.984 m | 2.052 m | +68.5 mm |
| Revs / km | 504.1 | 487.3 | -16.8 |
| Ground clearance | reference | +10.9 mm | +10.9 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.5 km/h | +3.45 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 103.5 km/h after switching to 245/40 R18 — a +3.45% 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 +10.9 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 R16
Back to
245/40 R18
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