Comparison
255/45 R19 vs 275/40 R20
Plus-sizing from 255/45 R19 to 275/40 R20 keeps overall diameter close to factory while opening room for a larger 20-inch wheel. This swap trims or stretches rolling diameter by a small margin.
The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. Visually, the bigger wheel fills the arch and gives the car a more aggressive stance. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 275/40 R20 is 15.9 mm taller than 255/45 R19, shifting the speedometer by +2.23%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+15.9 mm
2.23%
Speedometer at 100
102.2 km/h
+2.23% error
Ground clearance
+8.0 mm
ride height delta
Sidewall change
-4.8 mm
revs/km: 437.2
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/compare/255-45-r19-vs-275-40-r20Detailed comparison
| Metric | 255/45 R19 | 275/40 R20 | Difference |
|---|---|---|---|
| Overall diameter | 712.1 mm | 728.0 mm | +15.9 mm (+2.23%) |
| Sidewall height | 114.8 mm | 110.0 mm | -4.8 mm |
| Circumference | 2.237 m | 2.287 m | +50.0 mm |
| Revs / km | 447.0 | 437.2 | -9.8 |
| Ground clearance | reference | +8.0 mm | +8.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.2 km/h | +2.23 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 102.2 km/h after switching to 275/40 R20 — a +2.23% 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 +8.0 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
255/45 R19
Back to
275/40 R20
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