Comparison
205/55 R16 vs 245/40 R18
Plus-sizing from 205/55 R16 to 245/40 R18 keeps overall diameter close to factory while opening room for a larger 18-inch wheel. This wheel and tire pairing swings rolling diameter far enough to feel on the road. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides.
The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 245/40 R18 is 21.3 mm taller than 205/55 R16, shifting the speedometer by +3.37%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+21.3 mm
3.37%
Speedometer at 100
103.4 km/h
+3.37% error
Ground clearance
+10.7 mm
ride height delta
Sidewall change
-14.8 mm
revs/km: 487.3
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/compare/205-55-r16-vs-245-40-r18Detailed comparison
| Metric | 205/55 R16 | 245/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 631.9 mm | 653.2 mm | +21.3 mm (+3.37%) |
| Sidewall height | 112.8 mm | 98.0 mm | -14.8 mm |
| Circumference | 1.985 m | 2.052 m | +66.9 mm |
| Revs / km | 503.7 | 487.3 | -16.4 |
| Ground clearance | reference | +10.7 mm | +10.7 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.4 km/h | +3.37 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 103.4 km/h after switching to 245/40 R18 — a +3.37% 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 +10.7 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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205/55 R16
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245/40 R18
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