Originally Posted by
ArgoMan
Hey all, I'm building out my TT bike anew with an 11-speed set up. I have a bead on a NOS Ultegra R6800 rear derailleur and a very good condition used R8000 RD. There's about a $30 difference, with the 6800 being the cheaper part. I see that Shimano incorporated a "Shadow" technology into the 8000 - I have no idea what that is. Any hoo, is there a big difference in the performance of the RDs? I don't mind spending an extra few bucks for the used R8000 if it will perform a lot better. Thank you!
I don't think that extra $30 will make an appreciable difference in your intended usage. The "Shadow RD" is just tucked further inside the drive side dropout than a standard RD, see the image from the Shimano site...
If that 12mm is critical to you and worth $30, then jump on it. If you don't mind the protrusion of the non-Shadow RD, save yourself the $30.