I had 2 x Supersix HM frames (2013 model) delivered with faulty rear dropouts, with 25s in it was clear they weren't straight (less obvious with 23s). Whilst negotiating with the shop to get them to send me a non-faulty frame they told me that Cannondale would invalidate the warranty if I was running 25s on it, I guess that remains the case with all models until this years redesign... I now run 23s on reasonably wide rims which sit fine.
I had 2 x Supersix HM frames (2013 model) delivered with faulty rear dropouts, with 25s in it was clear they weren't straight (less obvious with 23s). Whilst negotiating with the shop to get them to send me a non-faulty frame they told me that Cannondale would invalidate the warranty if I was running 25s on it, I guess that remains the case with all models until this years redesign... I now run 23s on reasonably wide rims which sit fine.