Comparison
225/40 R19 vs 235/40 R18
Switching from 225/40 R19 to 235/40 R18 steps down to a 18-inch wheel — a familiar move for winter and dedicated all-terrain sets. This tire combination shifts overall diameter slightly from OEM. The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakePractical direction for winter wheels, chains, or rougher pavement where cushioning matters.
Quick math: 235/40 R18 is 17.4 mm shorter than 225/40 R19, shifting the speedometer by -2.63%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-17.4 mm
-2.63%
Speedometer at 100
97.4 km/h
-2.63% error
Ground clearance
-8.7 mm
ride height delta
Sidewall change
+4.0 mm
revs/km: 493.4
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/compare/225-40-r19-vs-235-40-r18Detailed comparison
| Metric | 225/40 R19 | 235/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 662.6 mm | 645.2 mm | -17.4 mm (-2.63%) |
| Sidewall height | 90.0 mm | 94.0 mm | +4.0 mm |
| Circumference | 2.082 m | 2.027 m | -54.7 mm |
| Revs / km | 480.4 | 493.4 | +13.0 |
| Ground clearance | reference | -8.7 mm | -8.7 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.4 km/h | -2.63 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 97.4 km/h after switching to 235/40 R18 — a -2.63% 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 -8.7 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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225/40 R19
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235/40 R18
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