Comparison
215/40 R18 vs 275/35 R18
275/35 R18 is a wider variation of 215/40 R18 on the same 18-inch rim, adding 60 mm of tread footprint. This setup noticeably changes overall diameter compared to OEM. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeUseful when extra dry grip and stance matter more than a small fuel-economy hit.
Quick math: 275/35 R18 is 20.5 mm taller than 215/40 R18, shifting the speedometer by +3.26%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+20.5 mm
3.26%
Speedometer at 100
103.3 km/h
+3.26% error
Ground clearance
+10.3 mm
ride height delta
Sidewall change
+10.3 mm
revs/km: 489.9
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/compare/215-40-r18-vs-275-35-r18Detailed comparison
| Metric | 215/40 R18 | 275/35 R18 | Difference |
|---|---|---|---|
| Overall diameter | 629.2 mm | 649.7 mm | +20.5 mm (+3.26%) |
| Sidewall height | 86.0 mm | 96.3 mm | +10.3 mm |
| Circumference | 1.977 m | 2.041 m | +64.4 mm |
| Revs / km | 505.9 | 489.9 | -16.0 |
| Ground clearance | reference | +10.3 mm | +10.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.3 km/h | +3.26 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 103.3 km/h after switching to 275/35 R18 — a +3.26% 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 +10.3 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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215/40 R18
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275/35 R18
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