Comparison
265/35 R20 vs 265/40 R18
Going from 265/35 R20 to 265/40 R18 is a minus-2 setup that adds sidewall on a smaller 18-inch wheel. This setup moves rolling diameter well outside the usual OEM tolerance. Extra sidewall absorbs impacts more readily — a sensible bias for daily commuting and broken pavement.
Indicated speed will drift far enough that recalibration is worth considering. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 265/40 R18 is 24.3 mm shorter than 265/35 R20, shifting the speedometer by -3.50%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-24.3 mm
-3.50%
Speedometer at 100
96.5 km/h
-3.50% error
Ground clearance
-12.1 mm
ride height delta
Sidewall change
+13.3 mm
revs/km: 475.7
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/compare/265-35-r20-vs-265-40-r18Detailed comparison
| Metric | 265/35 R20 | 265/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 693.5 mm | 669.2 mm | -24.3 mm (-3.50%) |
| Sidewall height | 92.8 mm | 106.0 mm | +13.3 mm |
| Circumference | 2.179 m | 2.102 m | -76.3 mm |
| Revs / km | 459.0 | 475.7 | +16.7 |
| Ground clearance | reference | -12.1 mm | -12.1 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.5 km/h | -3.50 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 96.5 km/h after switching to 265/40 R18 — a -3.50% 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 -12.1 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.
Back to
265/35 R20
Back to
265/40 R18
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