Comparison
245/40 R20 vs 285/30 R20
Going from 245/40 R20 to 285/30 R20 keeps the rim but tightens the sidewall for a sportier look. This wheel and tire pairing noticeably changes overall diameter compared to OEM.
The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. 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 delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeSuits drivers who value sharper steering and appearance over outright ride softness.
Quick math: 285/30 R20 is 25.0 mm shorter than 245/40 R20, shifting the speedometer by -3.55%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-25.0 mm
-3.55%
Speedometer at 100
96.4 km/h
-3.55% error
Ground clearance
-12.5 mm
ride height delta
Sidewall change
-12.5 mm
revs/km: 468.8
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/compare/245-40-r20-vs-285-30-r20Detailed comparison
| Metric | 245/40 R20 | 285/30 R20 | Difference |
|---|---|---|---|
| Overall diameter | 704.0 mm | 679.0 mm | -25.0 mm (-3.55%) |
| Sidewall height | 98.0 mm | 85.5 mm | -12.5 mm |
| Circumference | 2.212 m | 2.133 m | -78.5 mm |
| Revs / km | 452.1 | 468.8 | +16.6 |
| Ground clearance | reference | -12.5 mm | -12.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.4 km/h | -3.55 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 96.4 km/h after switching to 285/30 R20 — a -3.55% 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 -12.5 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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245/40 R20
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285/30 R20
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