Comparison
285/35 R20 vs 305/30 R20
Stepping from 285/35 R20 to 305/30 R20 keeps the 20-inch wheel but widens the section by 20 mm. This wheel and tire pairing trims or stretches rolling diameter by a small margin.
Expect a slight but noticeable shift in indicated speed compared to the original tires. Expect a more planted steering feel, at the cost of some of the cushioning a taller sidewall provides. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. 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: 305/30 R20 is 16.5 mm shorter than 285/35 R20, shifting the speedometer by -2.33%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-16.5 mm
-2.33%
Speedometer at 100
97.7 km/h
-2.33% error
Ground clearance
-8.3 mm
ride height delta
Sidewall change
-8.3 mm
revs/km: 460.7
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/compare/285-35-r20-vs-305-30-r20Detailed comparison
| Metric | 285/35 R20 | 305/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 707.5 mm | 691.0 mm | -16.5 mm (-2.33%) |
| Sidewall height | 99.8 mm | 91.5 mm | -8.3 mm |
| Circumference | 2.223 m | 2.171 m | -51.8 mm |
| Revs / km | 449.9 | 460.7 | +10.7 |
| Ground clearance | reference | -8.3 mm | -8.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.7 km/h | -2.33 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 97.7 km/h after switching to 305/30 R20 — a -2.33% 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 -8.3 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.
Back to
285/35 R20
Back to
305/30 R20
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