Comparison
265/40 R21 vs 275/45 R20
Going from 265/40 R21 to 275/45 R20 is a minus-1 setup that adds sidewall on a smaller 20-inch wheel. This sizing approach barely shifts the rolling circumference.
Dashboard speed shifts only marginally — within the noise of normal OEM tolerance. The taller sidewall adds cushioning over potholes and rougher roads, with a softer overall ride. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. The smaller wheel is also lighter and easier to find affordable winter rubber for. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 275/45 R20 is 10.1 mm taller than 265/40 R21, shifting the speedometer by +1.35%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+10.1 mm
1.35%
Speedometer at 100
101.4 km/h
+1.35% error
Ground clearance
+5.1 mm
ride height delta
Sidewall change
+17.8 mm
revs/km: 421.3
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/compare/265-40-r21-vs-275-45-r20Detailed comparison
| Metric | 265/40 R21 | 275/45 R20 | Difference |
|---|---|---|---|
| Overall diameter | 745.4 mm | 755.5 mm | +10.1 mm (+1.35%) |
| Sidewall height | 106.0 mm | 123.8 mm | +17.8 mm |
| Circumference | 2.342 m | 2.373 m | +31.7 mm |
| Revs / km | 427.0 | 421.3 | -5.7 |
| Ground clearance | reference | +5.1 mm | +5.1 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.4 km/h | +1.35 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 101.4 km/h after switching to 275/45 R20 — a +1.35% 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 +5.1 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
265/40 R21
Back to
275/45 R20
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