Comparison
235/55 R18 vs 255/40 R19
Going from 235/55 R18 to 255/40 R19 steps up to a 19-inch rim while trimming sidewall to stay near OEM rolling diameter. This swap 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: 255/40 R19 is 29.1 mm shorter than 235/55 R18, shifting the speedometer by -4.07%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-29.1 mm
-4.07%
Speedometer at 100
95.9 km/h
-4.07% error
Ground clearance
-14.6 mm
ride height delta
Sidewall change
-27.3 mm
revs/km: 463.6
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/compare/235-55-r18-vs-255-40-r19Detailed comparison
| Metric | 235/55 R18 | 255/40 R19 | Difference |
|---|---|---|---|
| Overall diameter | 715.7 mm | 686.6 mm | -29.1 mm (-4.07%) |
| Sidewall height | 129.3 mm | 102.0 mm | -27.3 mm |
| Circumference | 2.248 m | 2.157 m | -91.4 mm |
| Revs / km | 444.8 | 463.6 | +18.8 |
| Ground clearance | reference | -14.6 mm | -14.6 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 95.9 km/h | -4.07 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 95.9 km/h after switching to 255/40 R19 — a -4.07% 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 -14.6 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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235/55 R18
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255/40 R19
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