I've looked quite a bit on the Serotta website, couldn't find the info. Maybe I'm just stupid... What are these '3D dropouts', how do I recognize them, when were they introduced ?

Thanks,

Pierre

The 3D dropouts were introduced late 99 early 2000 (give or take 6 months). They became "XL" in early 2001. They use the same concept as a Breezer style dropout, that the chain and seatstays can be welded onto the dropout from any angle. Before that, all dropouts, not just Serotta's were little "L" looking devices that were unique angles to each frame size.

The idea is that you only need one dropout to build with any size frame. For a custom manufacturer that makes things very easy. Their "dual ear" dropout - also the 3D XL dropout is a nice wide perch for the end of the seat/chainstay to be welded to, making a very strong joint.

The reason why they are called XL now is because the hole in the middle is larger then when the dropouts were just "3D." Hope that helps.

Look at the dropout in the pic below, that is a 3D XL dropout

An added bit of info: the 3dXL dropouts were designed and developed by Dave Kirk (the frame builder) while he was the head of R&D at Serotta.