Comparison
245/45 R19 vs 255/45 R18
Going from 245/45 R19 to 255/45 R18 is a minus-1 setup that adds sidewall on a smaller 18-inch wheel. This swap shifts overall diameter slightly from OEM. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff.
The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 255/45 R18 is 16.4 mm shorter than 245/45 R19, shifting the speedometer by -2.33%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-16.4 mm
-2.33%
Speedometer at 100
97.7 km/h
-2.33% error
Ground clearance
-8.2 mm
ride height delta
Sidewall change
+4.5 mm
revs/km: 463.5
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/compare/245-45-r19-vs-255-45-r18Detailed comparison
| Metric | 245/45 R19 | 255/45 R18 | Difference |
|---|---|---|---|
| Overall diameter | 703.1 mm | 686.7 mm | -16.4 mm (-2.33%) |
| Sidewall height | 110.3 mm | 114.8 mm | +4.5 mm |
| Circumference | 2.209 m | 2.157 m | -51.5 mm |
| Revs / km | 452.7 | 463.5 | +10.8 |
| Ground clearance | reference | -8.2 mm | -8.2 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.7 km/h | -2.33 km/h |
Verdict: excellent
Within ±3% — speedometer, ABS and traction control should behave normally.
Speedometer impact
At a true 100 km/h, your dashboard will read 97.7 km/h after switching to 255/45 R18 — a -2.33% 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 -8.2 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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255/45 R18
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