Comparison
255/35 R20 vs 265/40 R20
265/40 R20 is a wider variation of 255/35 R20 on the same 20-inch rim, adding 10 mm of tread footprint. This sizing approach moves rolling diameter well outside the usual OEM tolerance. The taller sidewall adds cushioning over potholes and rougher roads, with a softer overall ride.
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.
TakeReasonable performance-leaning swap as long as fender and suspension clearance check out.
Quick math: 265/40 R20 is 33.5 mm taller than 255/35 R20, shifting the speedometer by +4.88%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+33.5 mm
4.88%
Speedometer at 100
104.9 km/h
+4.88% error
Ground clearance
+16.8 mm
ride height delta
Sidewall change
+16.8 mm
revs/km: 442.1
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/compare/255-35-r20-vs-265-40-r20Detailed comparison
| Metric | 255/35 R20 | 265/40 R20 | Difference |
|---|---|---|---|
| Overall diameter | 686.5 mm | 720.0 mm | +33.5 mm (+4.88%) |
| Sidewall height | 89.3 mm | 106.0 mm | +16.8 mm |
| Circumference | 2.157 m | 2.262 m | +105.2 mm |
| Revs / km | 463.7 | 442.1 | -21.6 |
| Ground clearance | reference | +16.8 mm | +16.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 104.9 km/h | +4.88 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 104.9 km/h after switching to 265/40 R20 — a +4.88% 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 +16.8 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.
Back to
255/35 R20
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265/40 R20
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