Comparison
245/45 R18 vs 275/35 R20
Switching from 245/45 R18 to 275/35 R20 is a plus-2 upgrade that wraps a shorter sidewall around a larger 20-inch wheel. This wheel and tire pairing noticeably changes overall diameter compared to OEM. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement.
Indicated speed will drift far enough that recalibration is worth considering. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeA solid pick for drivers chasing a more aggressive stance without abandoning OEM rolling diameter.
Quick math: 275/35 R20 is 22.8 mm taller than 245/45 R18, shifting the speedometer by +3.36%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+22.8 mm
3.36%
Speedometer at 100
103.4 km/h
+3.36% error
Ground clearance
+11.4 mm
ride height delta
Sidewall change
-14.0 mm
revs/km: 454.4
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/compare/245-45-r18-vs-275-35-r20Detailed comparison
| Metric | 245/45 R18 | 275/35 R20 | Difference |
|---|---|---|---|
| Overall diameter | 677.7 mm | 700.5 mm | +22.8 mm (+3.36%) |
| Sidewall height | 110.3 mm | 96.3 mm | -14.0 mm |
| Circumference | 2.129 m | 2.201 m | +71.6 mm |
| Revs / km | 469.7 | 454.4 | -15.3 |
| Ground clearance | reference | +11.4 mm | +11.4 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.4 km/h | +3.36 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 103.4 km/h after switching to 275/35 R20 — a +3.36% 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 +11.4 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
245/45 R18
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275/35 R20
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