Comparison
245/45 R19 vs 255/55 R18
Switching from 245/45 R19 to 255/55 R18 steps down to a 18-inch wheel — a familiar move for winter and dedicated all-terrain sets. This alternative fitment moves rolling diameter well outside the usual OEM tolerance.
Indicated speed will drift far enough that recalibration is worth considering. The taller sidewall adds cushioning over potholes and rougher roads, with a softer overall ride. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. The smaller wheel is also lighter and easier to find affordable winter rubber for. 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: 255/55 R18 is 34.6 mm taller than 245/45 R19, shifting the speedometer by +4.92%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+34.6 mm
4.92%
Speedometer at 100
104.9 km/h
+4.92% error
Ground clearance
+17.3 mm
ride height delta
Sidewall change
+30.0 mm
revs/km: 431.5
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/compare/245-45-r19-vs-255-55-r18Detailed comparison
| Metric | 245/45 R19 | 255/55 R18 | Difference |
|---|---|---|---|
| Overall diameter | 703.1 mm | 737.7 mm | +34.6 mm (+4.92%) |
| Sidewall height | 110.3 mm | 140.3 mm | +30.0 mm |
| Circumference | 2.209 m | 2.318 m | +108.7 mm |
| Revs / km | 452.7 | 431.5 | -21.2 |
| Ground clearance | reference | +17.3 mm | +17.3 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 104.9 km/h | +4.92 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 104.9 km/h after switching to 255/55 R18 — a +4.92% 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 +17.3 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.
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245/45 R19
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255/55 R18
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