Comparison
255/35 R20 vs 285/30 R20
285/30 R20 is a wider variation of 255/35 R20 on the same 20-inch rim, adding 30 mm of tread footprint. This swap barely shifts the rolling circumference.
Dashboard speed shifts only marginally — within the noise of normal OEM tolerance. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeReasonable performance-leaning swap as long as fender and suspension clearance check out.
Quick math: 285/30 R20 is 7.5 mm shorter than 255/35 R20, shifting the speedometer by -1.09%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-7.5 mm
-1.09%
Speedometer at 100
98.9 km/h
-1.09% error
Ground clearance
-3.8 mm
ride height delta
Sidewall change
-3.8 mm
revs/km: 468.8
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/compare/255-35-r20-vs-285-30-r20Detailed comparison
| Metric | 255/35 R20 | 285/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 686.5 mm | 679.0 mm | -7.5 mm (-1.09%) |
| Sidewall height | 89.3 mm | 85.5 mm | -3.8 mm |
| Circumference | 2.157 m | 2.133 m | -23.6 mm |
| Revs / km | 463.7 | 468.8 | +5.1 |
| Ground clearance | reference | -3.8 mm | -3.8 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 98.9 km/h | -1.09 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 98.9 km/h after switching to 285/30 R20 — a -1.09% 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 -3.8 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.
Back to
255/35 R20
Back to
285/30 R20
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