Comparison
255/45 R19 vs 285/30 R20
Plus-sizing from 255/45 R19 to 285/30 R20 keeps overall diameter close to factory while opening room for a larger 20-inch wheel. This setup swings rolling diameter far enough to feel on the road. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 285/30 R20 is 33.1 mm shorter than 255/45 R19, shifting the speedometer by -4.65%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-33.1 mm
-4.65%
Speedometer at 100
95.4 km/h
-4.65% error
Ground clearance
-16.5 mm
ride height delta
Sidewall change
-29.3 mm
revs/km: 468.8
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/compare/255-45-r19-vs-285-30-r20Detailed comparison
| Metric | 255/45 R19 | 285/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 712.1 mm | 679.0 mm | -33.1 mm (-4.65%) |
| Sidewall height | 114.8 mm | 85.5 mm | -29.3 mm |
| Circumference | 2.237 m | 2.133 m | -104.0 mm |
| Revs / km | 447.0 | 468.8 | +21.8 |
| Ground clearance | reference | -16.5 mm | -16.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 95.4 km/h | -4.65 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 95.4 km/h after switching to 285/30 R20 — a -4.65% 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 -16.5 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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255/45 R19
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285/30 R20
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