Comparison
275/35 R18 vs 275/40 R18
Switching from 275/35 R18 to 275/40 R18 keeps the wheel but adds sidewall for extra cushioning. This wheel and tire pairing swings rolling diameter far enough to feel on the road. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. More sidewall typically improves comfort and curb protection, especially on city streets. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeA comfort-leaning direction that's easier on wheels and suspension over rough surfaces.
Quick math: 275/40 R18 is 27.5 mm taller than 275/35 R18, shifting the speedometer by +4.23%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+27.5 mm
4.23%
Speedometer at 100
104.2 km/h
+4.23% error
Ground clearance
+13.8 mm
ride height delta
Sidewall change
+13.8 mm
revs/km: 470.0
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/compare/275-35-r18-vs-275-40-r18Detailed comparison
| Metric | 275/35 R18 | 275/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 649.7 mm | 677.2 mm | +27.5 mm (+4.23%) |
| Sidewall height | 96.3 mm | 110.0 mm | +13.8 mm |
| Circumference | 2.041 m | 2.127 m | +86.4 mm |
| Revs / km | 489.9 | 470.0 | -19.9 |
| Ground clearance | reference | +13.8 mm | +13.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 104.2 km/h | +4.23 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 104.2 km/h after switching to 275/40 R18 — a +4.23% 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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275/35 R18
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275/40 R18
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