Comparison
285/30 R20 vs 285/35 R20
Switching from 285/30 R20 to 285/35 R20 keeps the wheel but adds sidewall for extra cushioning. This swap moves rolling diameter well outside the usual OEM tolerance. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. The taller sidewall adds cushioning over potholes and rougher roads, with a softer overall ride. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeA comfort-leaning direction that's easier on wheels and suspension over rough surfaces.
Quick math: 285/35 R20 is 28.5 mm taller than 285/30 R20, shifting the speedometer by +4.20%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+28.5 mm
4.20%
Speedometer at 100
104.2 km/h
+4.20% error
Ground clearance
+14.3 mm
ride height delta
Sidewall change
+14.3 mm
revs/km: 449.9
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/compare/285-30-r20-vs-285-35-r20Detailed comparison
| Metric | 285/30 R20 | 285/35 R20 | Difference |
|---|---|---|---|
| Overall diameter | 679.0 mm | 707.5 mm | +28.5 mm (+4.20%) |
| Sidewall height | 85.5 mm | 99.8 mm | +14.3 mm |
| Circumference | 2.133 m | 2.223 m | +89.5 mm |
| Revs / km | 468.8 | 449.9 | -18.9 |
| Ground clearance | reference | +14.3 mm | +14.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 104.2 km/h | +4.20 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 104.2 km/h after switching to 285/35 R20 — a +4.20% 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 +14.3 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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285/30 R20
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285/35 R20
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