pavemnt said:
As far as I know, the C40HP and the early C50HP have the same stays. Then, if I remember right, they changed the profile of the C50 stay a little, so that the diamond is more refined and has a lower profile than the original version.
The C40 and C50 both had the diamond chainstays, which was a unique advertising feature about them. Supposedly it helped dampen the ride quality, and one certainly can't complain about the comfortable, 'magical' ride quality of the C50.
However I think it was a bear to manufacture, as you had to wrap the carbon fiber around that diamond opening. I believe the later C50s (sometime after 2005) came with the spoon-shaped chainstay that you see on current Colnagos like the EPS. What I like about this chainstay is Colnago took advantage of the wide shape to add more artwork here. I may be a bit off-base here and maybe Colnago just removed the hole from the diamond. I know the spoon-shaped chainstay debuted on the old EPSs.
Another problem with the diamond chainstay is standard chain guard patches won't fit properly. It would be nice if Colnago provided chain patches standard on their frames like with Pinarello, Ridley, and other manufacturers.