Comparison
225/55 R18 vs 275/40 R18
Switching from 225/55 R18 to 275/40 R18 drops the aspect ratio by 15 points on the same 18-inch wheel. This wheel and tire pairing moves rolling diameter well outside the usual OEM tolerance. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeSuits drivers who value sharper steering and appearance over outright ride softness.
Quick math: 275/40 R18 is 27.5 mm shorter than 225/55 R18, shifting the speedometer by -3.90%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-27.5 mm
-3.90%
Speedometer at 100
96.1 km/h
-3.90% error
Ground clearance
-13.8 mm
ride height delta
Sidewall change
-13.8 mm
revs/km: 470.0
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/compare/225-55-r18-vs-275-40-r18Detailed comparison
| Metric | 225/55 R18 | 275/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 704.7 mm | 677.2 mm | -27.5 mm (-3.90%) |
| Sidewall height | 123.8 mm | 110.0 mm | -13.8 mm |
| Circumference | 2.214 m | 2.127 m | -86.4 mm |
| Revs / km | 451.7 | 470.0 | +18.3 |
| Ground clearance | reference | -13.8 mm | -13.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.1 km/h | -3.90 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 96.1 km/h after switching to 275/40 R18 — a -3.90% 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 -13.8 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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225/55 R18
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275/40 R18
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