Comparison
255/40 R19 vs 275/40 R18
275/40 R18 drops the rim from 19 to 18 inches versus 255/40 R19, trading wheel size for taller sidewall. This tire combination keeps overall diameter very close to stock.
Dashboard speed shifts only marginally — within the noise of normal OEM tolerance. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. The smaller wheel is also lighter and easier to find affordable winter rubber for. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 275/40 R18 is 9.4 mm shorter than 255/40 R19, shifting the speedometer by -1.37%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-9.4 mm
-1.37%
Speedometer at 100
98.6 km/h
-1.37% error
Ground clearance
-4.7 mm
ride height delta
Sidewall change
+8.0 mm
revs/km: 470.0
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/compare/255-40-r19-vs-275-40-r18Detailed comparison
| Metric | 255/40 R19 | 275/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 686.6 mm | 677.2 mm | -9.4 mm (-1.37%) |
| Sidewall height | 102.0 mm | 110.0 mm | +8.0 mm |
| Circumference | 2.157 m | 2.127 m | -29.5 mm |
| Revs / km | 463.6 | 470.0 | +6.4 |
| Ground clearance | reference | -4.7 mm | -4.7 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 98.6 km/h | -1.37 km/h |
Verdict: excellent
Within ±3% — speedometer, ABS and traction control should behave normally.
Speedometer impact
At a true 100 km/h, your dashboard will read 98.6 km/h after switching to 275/40 R18 — a -1.37% 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 -4.7 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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255/40 R19
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275/40 R18
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