Comparison
225/50 R18 vs 255/40 R18
Going from 225/50 R18 to 255/40 R18 keeps the rim but tightens the sidewall for a sportier look. This wheel and tire pairing moves rolling diameter well outside the usual OEM tolerance.
The speedometer error is noticeable and may warrant a recalibration if you rely on indicated speed. Less sidewall flex usually translates to crisper turn-in and a slightly stiffer ride over rough pavement. The wider section adds contact patch and lateral stability, while eating into fender and suspension clearance. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeSuits drivers who value sharper steering and appearance over outright ride softness.
Quick math: 255/40 R18 is 21.0 mm shorter than 225/50 R18, shifting the speedometer by -3.08%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
-21.0 mm
-3.08%
Speedometer at 100
96.9 km/h
-3.08% error
Ground clearance
-10.5 mm
ride height delta
Sidewall change
-10.5 mm
revs/km: 481.4
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/compare/225-50-r18-vs-255-40-r18Detailed comparison
| Metric | 225/50 R18 | 255/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 682.2 mm | 661.2 mm | -21.0 mm (-3.08%) |
| Sidewall height | 112.5 mm | 102.0 mm | -10.5 mm |
| Circumference | 2.143 m | 2.077 m | -66.0 mm |
| Revs / km | 466.6 | 481.4 | +14.8 |
| Ground clearance | reference | -10.5 mm | -10.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 96.9 km/h | -3.08 km/h |
Verdict: warning
Between 3% and 5% — noticeable speedometer drift; recalibration may be advisable.
Speedometer impact
At a true 100 km/h, your dashboard will read 96.9 km/h after switching to 255/40 R18 — a -3.08% 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 -10.5 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.
Back to
225/50 R18
Back to
255/40 R18
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