Comparison
225/45 R18 vs 285/30 R20
Going from 225/45 R18 to 285/30 R20 steps up to a 20-inch rim while trimming sidewall to stay near OEM rolling diameter. This wheel and tire pairing 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. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 285/30 R20 is 19.3 mm taller than 225/45 R18, shifting the speedometer by +2.93%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+19.3 mm
2.93%
Speedometer at 100
102.9 km/h
+2.93% error
Ground clearance
+9.6 mm
ride height delta
Sidewall change
-15.8 mm
revs/km: 468.8
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/compare/225-45-r18-vs-285-30-r20Detailed comparison
| Metric | 225/45 R18 | 285/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 659.7 mm | 679.0 mm | +19.3 mm (+2.93%) |
| Sidewall height | 101.3 mm | 85.5 mm | -15.8 mm |
| Circumference | 2.073 m | 2.133 m | +60.6 mm |
| Revs / km | 482.5 | 468.8 | -13.7 |
| Ground clearance | reference | +9.6 mm | +9.6 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.9 km/h | +2.93 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 102.9 km/h after switching to 285/30 R20 — a +2.93% 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 +9.6 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
225/45 R18
Back to
285/30 R20
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