Comparison
255/40 R18 vs 275/35 R18
On the same 18-inch wheel, 275/35 R18 grows the section width by 20 mm versus 255/40 R18. This sizing approach shifts overall diameter slightly from OEM.
Expect a slight but noticeable shift in indicated speed compared to the original tires. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeUseful when extra dry grip and stance matter more than a small fuel-economy hit.
Quick math: 275/35 R18 is 11.5 mm shorter than 255/40 R18, shifting the speedometer by -1.74%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-11.5 mm
-1.74%
Speedometer at 100
98.3 km/h
-1.74% error
Ground clearance
-5.8 mm
ride height delta
Sidewall change
-5.8 mm
revs/km: 489.9
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/compare/255-40-r18-vs-275-35-r18Detailed comparison
| Metric | 255/40 R18 | 275/35 R18 | Difference |
|---|---|---|---|
| Overall diameter | 661.2 mm | 649.7 mm | -11.5 mm (-1.74%) |
| Sidewall height | 102.0 mm | 96.3 mm | -5.8 mm |
| Circumference | 2.077 m | 2.041 m | -36.1 mm |
| Revs / km | 481.4 | 489.9 | +8.5 |
| Ground clearance | reference | -5.8 mm | -5.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 98.3 km/h | -1.74 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 98.3 km/h after switching to 275/35 R18 — a -1.74% 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 -5.8 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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255/40 R18
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275/35 R18
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