Comparison
235/40 R19 vs 245/40 R18
245/40 R18 drops the rim from 19 to 18 inches versus 235/40 R19, trading wheel size for taller sidewall. This tire combination shifts overall diameter slightly from OEM. Expect a slight but noticeable shift in indicated speed compared to the original tires. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. 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: 245/40 R18 is 17.4 mm shorter than 235/40 R19, shifting the speedometer by -2.59%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-17.4 mm
-2.59%
Speedometer at 100
97.4 km/h
-2.59% error
Ground clearance
-8.7 mm
ride height delta
Sidewall change
+4.0 mm
revs/km: 487.3
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/compare/235-40-r19-vs-245-40-r18Detailed comparison
| Metric | 235/40 R19 | 245/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 670.6 mm | 653.2 mm | -17.4 mm (-2.59%) |
| Sidewall height | 94.0 mm | 98.0 mm | +4.0 mm |
| Circumference | 2.107 m | 2.052 m | -54.7 mm |
| Revs / km | 474.7 | 487.3 | +12.6 |
| Ground clearance | reference | -8.7 mm | -8.7 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 97.4 km/h | -2.59 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 245/40 R18 — a -2.59% 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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235/40 R19
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245/40 R18
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