just from looking at the picture you posted it actually does look like you may have rubbed against a curb or something... it shows scratches and significant wear around the crack... (unless it's a reflection or something similar that is showing up on the photo)

honestly, just from looking at it, if I were the dealer I would have said the same!

remember, these are alloy rims...they are light and a bit fragile... and they scratch easily... will they crack easily??? probably not but i've seen cracked alloy rims caused by hitting small potholes..

rubbing hard against curbs can also give you the exact same results!

not saying you did that but these wheels are not as durable as the stock ones and they are a huge difference (lighter and weaker) compared to wheels made years ago.

if you can get the dealer to swap it go for it... he may do so if the vehicle has low mileage and you've only had her for a short period of time...

if it's been more than a few weeks or months then forget it... he won't do it!

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2012 X5 50i M-Sport
2014 X3 35i M-Sport