I recently purchased Giant’s new TCX Advanced Pro 1 and it came with Ultegra Di2 and Shimano’s new hydraulic road disc brakes. Coming from racing SRAM last year I immediately missed the retention and lack of noise a clutch provides off road so I picked up the new XTR Di2 rear derailleur.
If you keep your firmware up to date the XTR Di2 should be plug and play. You’ll need to set your limit screws and b-tension properly and maybe adjust the spacing by holding the button on the junction box and following the 4th gear procedure. You can also do this using the eTube software where you can also make other changes and update firmware. I setup my shifters to operate similar to how the new SRAM wireless is rumored to, the right shifts down and the left shifts up, as I’m running 1×11.
Some things to consider… If you have a road front derailleur the XTR rear derailleur will not work. The shifters will work with both road and mountain Di2, but only if the rest of the drivetrain is matched. Also, depending on your bike the angle of the derailleur hanger may cause issues with b-tension and spacing between the jockey wheel and cogs. The XTR Di2 derailleur has a b-axle that spaces the derailleur away from the frame and is where it rests on the derailleur hanger. Ideally this would be perpendicular to the hanger for normal operation. However, on my bike the derailleur has to be run with the b-axle in a second position nearly in line with the seat stay in order to get the spacing right and I had to reverse the b-tension screw.
While shifting is now really good it comes with a caveat, I can’t remove the rear wheel with the derailleur installed. The design of the b-axle doesn’t allow the derailleur to pivot back far enough, hitting an integral stop in the derailleur. The opposite holds true with the b-axle in the regular position and it’s not allowed to pivot close enough to the cogs. I’m hoping other bikes won’t have this issue but it’s something to keep in mind. It also makes the derailleur look a little weird in operation compared to a traditional position.
My verdict for should you do this..? Yes. But only if you’re dead set on running Shimano on your CX bike. The shifting is pretty good with the chain quiet and secure. Since I will switch bikes before a wheel in cyclocross I could live with the issues but I’m switching to SRAM on my TCX. This is partly so both my bikes have matching groupsets and my hands fit the SRAM HydroR hoods a lot better than Shimano.