Comparison
255/55 R18 vs 275/45 R20
Switching from 255/55 R18 to 275/45 R20 is a plus-2 upgrade that wraps a shorter sidewall around a larger 20-inch wheel. This wheel and tire pairing shifts overall diameter slightly from OEM.
Expect a slight but noticeable shift in indicated speed compared to the original tires. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides. The wider section adds contact patch and lateral stability, while eating into fender and suspension clearance. The larger wheel shows more of the brake hardware and tightens up the wheel-gap look. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 275/45 R20 is 17.8 mm taller than 255/55 R18, shifting the speedometer by +2.41%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+17.8 mm
2.41%
Speedometer at 100
102.4 km/h
+2.41% error
Ground clearance
+8.9 mm
ride height delta
Sidewall change
-16.5 mm
revs/km: 421.3
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/compare/255-55-r18-vs-275-45-r20Detailed comparison
| Metric | 255/55 R18 | 275/45 R20 | Difference |
|---|---|---|---|
| Overall diameter | 737.7 mm | 755.5 mm | +17.8 mm (+2.41%) |
| Sidewall height | 140.3 mm | 123.8 mm | -16.5 mm |
| Circumference | 2.318 m | 2.373 m | +55.9 mm |
| Revs / km | 431.5 | 421.3 | -10.2 |
| Ground clearance | reference | +8.9 mm | +8.9 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.4 km/h | +2.41 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 102.4 km/h after switching to 275/45 R20 — a +2.41% 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 +8.9 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
255/55 R18
Back to
275/45 R20
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