Comparison
215/40 R18 vs 225/40 R18
225/40 R18 is a wider variation of 215/40 R18 on the same 18-inch rim, adding 10 mm of tread footprint. This sizing approach preserves rolling diameter within a hair of the original. Dashboard speed shifts only marginally — within the noise of normal OEM tolerance. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeUseful when extra dry grip and stance matter more than a small fuel-economy hit.
Quick math: 225/40 R18 is 8.0 mm taller than 215/40 R18, shifting the speedometer by +1.27%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+8.0 mm
1.27%
Speedometer at 100
101.3 km/h
+1.27% error
Ground clearance
+4.0 mm
ride height delta
Sidewall change
+4.0 mm
revs/km: 499.5
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/compare/215-40-r18-vs-225-40-r18Detailed comparison
| Metric | 215/40 R18 | 225/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 629.2 mm | 637.2 mm | +8.0 mm (+1.27%) |
| Sidewall height | 86.0 mm | 90.0 mm | +4.0 mm |
| Circumference | 1.977 m | 2.002 m | +25.1 mm |
| Revs / km | 505.9 | 499.5 | -6.4 |
| Ground clearance | reference | +4.0 mm | +4.0 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 101.3 km/h | +1.27 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 101.3 km/h after switching to 225/40 R18 — a +1.27% 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 +4.0 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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215/40 R18
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225/40 R18
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