Comparison
245/35 R20 vs 285/35 R20
285/35 R20 is a wider variation of 245/35 R20 on the same 20-inch rim, adding 40 mm of tread footprint. 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. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeReasonable performance-leaning swap as long as fender and suspension clearance check out.
Quick math: 285/35 R20 is 28.0 mm taller than 245/35 R20, shifting the speedometer by +4.12%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+28.0 mm
4.12%
Speedometer at 100
104.1 km/h
+4.12% error
Ground clearance
+14.0 mm
ride height delta
Sidewall change
+14.0 mm
revs/km: 449.9
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/compare/245-35-r20-vs-285-35-r20Detailed comparison
| Metric | 245/35 R20 | 285/35 R20 | Difference |
|---|---|---|---|
| Overall diameter | 679.5 mm | 707.5 mm | +28.0 mm (+4.12%) |
| Sidewall height | 85.8 mm | 99.8 mm | +14.0 mm |
| Circumference | 2.135 m | 2.223 m | +88.0 mm |
| Revs / km | 468.4 | 449.9 | -18.5 |
| Ground clearance | reference | +14.0 mm | +14.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 104.1 km/h | +4.12 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 104.1 km/h after switching to 285/35 R20 — a +4.12% 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 +14.0 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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245/35 R20
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285/35 R20
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