Comparison
245/45 R20 vs 245/60 R18
Minus-sizing from 245/45 R20 to 245/60 R18 pairs a smaller 18-inch wheel with more rubber between the rim and road. This alternative fitment noticeably changes overall diameter compared to OEM. The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. More sidewall typically improves comfort and curb protection, especially on city streets. Diameter delta falls in the cautious 3–5% range, where speedometer recalibration and a careful clearance check are worth doing.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 245/60 R18 is 22.7 mm taller than 245/45 R20, shifting the speedometer by +3.12%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+22.7 mm
3.12%
Speedometer at 100
103.1 km/h
+3.12% error
Ground clearance
+11.4 mm
ride height delta
Sidewall change
+36.8 mm
revs/km: 423.7
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/compare/245-45-r20-vs-245-60-r18Detailed comparison
| Metric | 245/45 R20 | 245/60 R18 | Difference |
|---|---|---|---|
| Overall diameter | 728.5 mm | 751.2 mm | +22.7 mm (+3.12%) |
| Sidewall height | 110.3 mm | 147.0 mm | +36.8 mm |
| Circumference | 2.289 m | 2.360 m | +71.3 mm |
| Revs / km | 436.9 | 423.7 | -13.2 |
| Ground clearance | reference | +11.4 mm | +11.4 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.1 km/h | +3.12 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 103.1 km/h after switching to 245/60 R18 — a +3.12% 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 +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.
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245/45 R20
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245/60 R18
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