Comparison
225/55 R18 vs 285/30 R20
285/30 R20 is a plus-2 alternative to 225/55 R18 — the bigger wheel shows through a thinner sidewall. This tire combination swings rolling diameter far enough to feel on the road.
Indicated speed will drift far enough that recalibration is worth considering. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. The larger wheel shows more of the brake hardware and tightens up the wheel-gap look. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 285/30 R20 is 25.7 mm shorter than 225/55 R18, shifting the speedometer by -3.65%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-25.7 mm
-3.65%
Speedometer at 100
96.4 km/h
-3.65% error
Ground clearance
-12.9 mm
ride height delta
Sidewall change
-38.3 mm
revs/km: 468.8
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/compare/225-55-r18-vs-285-30-r20Detailed comparison
| Metric | 225/55 R18 | 285/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 704.7 mm | 679.0 mm | -25.7 mm (-3.65%) |
| Sidewall height | 123.8 mm | 85.5 mm | -38.3 mm |
| Circumference | 2.214 m | 2.133 m | -80.7 mm |
| Revs / km | 451.7 | 468.8 | +17.1 |
| Ground clearance | reference | -12.9 mm | -12.9 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.4 km/h | -3.65 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 96.4 km/h after switching to 285/30 R20 — a -3.65% 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 -12.9 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
225/55 R18
Back to
285/30 R20
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