Comparison
275/35 R20 vs 285/30 R20
On the same 20-inch wheel, 285/30 R20 grows the section width by 10 mm versus 275/35 R20. This alternative fitment noticeably changes overall diameter compared to OEM. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. The shorter sidewall gives the tire a firmer, more responsive feel and sharpens steering input. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeUseful when extra dry grip and stance matter more than a small fuel-economy hit.
Quick math: 285/30 R20 is 21.5 mm shorter than 275/35 R20, shifting the speedometer by -3.07%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-21.5 mm
-3.07%
Speedometer at 100
96.9 km/h
-3.07% error
Ground clearance
-10.8 mm
ride height delta
Sidewall change
-10.8 mm
revs/km: 468.8
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/compare/275-35-r20-vs-285-30-r20Detailed comparison
| Metric | 275/35 R20 | 285/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 700.5 mm | 679.0 mm | -21.5 mm (-3.07%) |
| Sidewall height | 96.3 mm | 85.5 mm | -10.8 mm |
| Circumference | 2.201 m | 2.133 m | -67.5 mm |
| Revs / km | 454.4 | 468.8 | +14.4 |
| Ground clearance | reference | -10.8 mm | -10.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.9 km/h | -3.07 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 96.9 km/h after switching to 285/30 R20 — a -3.07% 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 -10.8 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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275/35 R20
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285/30 R20
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