Comparison
265/40 R21 vs 275/40 R20
Minus-sizing from 265/40 R21 to 275/40 R20 pairs a smaller 20-inch wheel with more rubber between the rim and road. This tire combination trims or stretches rolling diameter by a small margin.
Expect a slight but noticeable shift in indicated speed compared to the original tires. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. Minus-sizing keeps replacement costs down and opens up a wider range of winter and all-terrain tires. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 275/40 R20 is 17.4 mm shorter than 265/40 R21, shifting the speedometer by -2.33%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-17.4 mm
-2.33%
Speedometer at 100
97.7 km/h
-2.33% error
Ground clearance
-8.7 mm
ride height delta
Sidewall change
+4.0 mm
revs/km: 437.2
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/compare/265-40-r21-vs-275-40-r20Detailed comparison
| Metric | 265/40 R21 | 275/40 R20 | Difference |
|---|---|---|---|
| Overall diameter | 745.4 mm | 728.0 mm | -17.4 mm (-2.33%) |
| Sidewall height | 106.0 mm | 110.0 mm | +4.0 mm |
| Circumference | 2.342 m | 2.287 m | -54.7 mm |
| Revs / km | 427.0 | 437.2 | +10.2 |
| Ground clearance | reference | -8.7 mm | -8.7 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.7 km/h | -2.33 km/h |
Verdict: excellent
Within ±3% — speedometer, ABS and traction control should behave normally.
Speedometer impact
At a true 100 km/h, your dashboard will read 97.7 km/h after switching to 275/40 R20 — a -2.33% 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 -8.7 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
265/40 R21
Back to
275/40 R20
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