Comparison
225/45 R19 vs 265/40 R18
Going from 225/45 R19 to 265/40 R18 is a minus-1 setup that adds sidewall on a smaller 18-inch wheel. This tire combination trims or stretches rolling diameter by a small margin. The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. 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: 265/40 R18 is 15.9 mm shorter than 225/45 R19, shifting the speedometer by -2.32%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-15.9 mm
-2.32%
Speedometer at 100
97.7 km/h
-2.32% error
Ground clearance
-7.9 mm
ride height delta
Sidewall change
+4.8 mm
revs/km: 475.7
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/compare/225-45-r19-vs-265-40-r18Detailed comparison
| Metric | 225/45 R19 | 265/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 685.1 mm | 669.2 mm | -15.9 mm (-2.32%) |
| Sidewall height | 101.3 mm | 106.0 mm | +4.8 mm |
| Circumference | 2.152 m | 2.102 m | -50.0 mm |
| Revs / km | 464.6 | 475.7 | +11.0 |
| Ground clearance | reference | -7.9 mm | -7.9 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.7 km/h | -2.32 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 265/40 R18 — a -2.32% 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 -7.9 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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225/45 R19
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265/40 R18
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