Comparison
225/45 R19 vs 235/45 R18
Switching from 225/45 R19 to 235/45 R18 steps down to a 18-inch wheel — a familiar move for winter and dedicated all-terrain sets. This swap trims or stretches rolling diameter by a small margin. 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.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 235/45 R18 is 16.4 mm shorter than 225/45 R19, shifting the speedometer by -2.39%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-16.4 mm
-2.39%
Speedometer at 100
97.6 km/h
-2.39% error
Ground clearance
-8.2 mm
ride height delta
Sidewall change
+4.5 mm
revs/km: 476.0
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/compare/225-45-r19-vs-235-45-r18Detailed comparison
| Metric | 225/45 R19 | 235/45 R18 | Difference |
|---|---|---|---|
| Overall diameter | 685.1 mm | 668.7 mm | -16.4 mm (-2.39%) |
| Sidewall height | 101.3 mm | 105.8 mm | +4.5 mm |
| Circumference | 2.152 m | 2.101 m | -51.5 mm |
| Revs / km | 464.6 | 476.0 | +11.4 |
| Ground clearance | reference | -8.2 mm | -8.2 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.6 km/h | -2.39 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 97.6 km/h after switching to 235/45 R18 — a -2.39% 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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225/45 R19
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235/45 R18
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