Comparison
265/40 R21 vs 265/50 R20
Switching from 265/40 R21 to 265/50 R20 steps down to a 20-inch wheel — a familiar move for winter and dedicated all-terrain sets. This swap swings rolling diameter far enough to feel on the road. Indicated speed will drift far enough that recalibration is worth considering. The taller sidewall adds cushioning over potholes and rougher roads, with a softer overall ride. 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: 265/50 R20 is 27.6 mm taller than 265/40 R21, shifting the speedometer by +3.70%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+27.6 mm
3.70%
Speedometer at 100
103.7 km/h
+3.70% error
Ground clearance
+13.8 mm
ride height delta
Sidewall change
+26.5 mm
revs/km: 411.8
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/compare/265-40-r21-vs-265-50-r20Detailed comparison
| Metric | 265/40 R21 | 265/50 R20 | Difference |
|---|---|---|---|
| Overall diameter | 745.4 mm | 773.0 mm | +27.6 mm (+3.70%) |
| Sidewall height | 106.0 mm | 132.5 mm | +26.5 mm |
| Circumference | 2.342 m | 2.428 m | +86.7 mm |
| Revs / km | 427.0 | 411.8 | -15.2 |
| Ground clearance | reference | +13.8 mm | +13.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.7 km/h | +3.70 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 103.7 km/h after switching to 265/50 R20 — a +3.70% 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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265/40 R21
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265/50 R20
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