I'm running 23mm Conti GP4000s on my C59. Even on older 15C rims, they measure 25mm. On the C59, I'm at the limit. If I tried to squeeze in a 25mm GP4000, it would probably be too close to the top of the fork.
It would seem reasonable that someone would want to install a 25mm or 28mm GP4000 on a modern wide rim. That would easily break 30mm of actual width.
Agree with it or not, this is the direction of the industry.
You'll say that that is not a race bike but an endurance bike. Well, I'm sure 99% of Colnagos are not raced and they are bought my older guys with the disposable income for a $4500 frameset.
Here where i live, C60 is cheaper then Pinarello Dogma F8, F10, Bianchi Oltre XR4, Specialissima even S-Works or at least same price...
Older guys with disposable income here buying Pinarello Dogma F10 or something else which is AERO. They are not interested about C60 since is not aero and heavy
And i cant understund why u need more then 25mm on frameset like C60 .. If u need wider tires on this kind of frameset, u are definetely on wrong framesets..
Very often im riding gran fondos (this season few times more then 200 km, longest about 250 km) and im using 23mm tires (Conti 4000 SII ) or 25mm Corsa G+ (i prefer 23 Conti's) on Shamal Ultra 15C and Corsa G+ Tub 25mm on Bora One 35 Tub..
The fastest setup in my case are 25mm Bora tubs then 23mm Conti 4000 on Shamals (the first one offer better grip and more comfortable) and slowest 25mm Vittoria Corsa G+on Shamals...
I really believe that wider then 25mm on racing frame (yes, C60 is racing frame), is part of marketing.....