Comparison
215/50 R17 vs 265/40 R18
Going from 215/50 R17 to 265/40 R18 steps up to a 18-inch rim while trimming sidewall to stay near OEM rolling diameter. This setup 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. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff. Visually, the bigger wheel fills the arch and gives the car a more aggressive stance. The 3–5% diameter gap puts this in caution territory: doable on many cars, but verify clearance and consider recalibration.
TakeCommon upgrade for sportier handling and a tighter wheel-gap look on the same vehicle.
Quick math: 265/40 R18 is 22.4 mm taller than 215/50 R17, shifting the speedometer by +3.46%.
Current Tire
New Tire
Ground line · scaled comparison
Slight Difference
Within ±5% — usable, recalibration recommended
Diameter change
+22.4 mm
3.46%
Speedometer at 100
103.5 km/h
+3.46% error
Ground clearance
+11.2 mm
ride height delta
Sidewall change
-1.5 mm
revs/km: 475.7
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/compare/215-50-r17-vs-265-40-r18Detailed comparison
| Metric | 215/50 R17 | 265/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 646.8 mm | 669.2 mm | +22.4 mm (+3.46%) |
| Sidewall height | 107.5 mm | 106.0 mm | -1.5 mm |
| Circumference | 2.032 m | 2.102 m | +70.4 mm |
| Revs / km | 492.1 | 475.7 | -16.5 |
| Ground clearance | reference | +11.2 mm | +11.2 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 103.5 km/h | +3.46 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 103.5 km/h after switching to 265/40 R18 — a +3.46% 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 +11.2 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.
Back to
215/50 R17
Back to
265/40 R18
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