So this past winter I upgraded my drive train to the Shimano GRX Di2 setup. I like it. I only did the right/rear due to my limited budget. But with this setup I'm wondering if I can get a 105 Di2 rear derailleur as a backup in case something happens. This will be my fifth Unbound Gravel event and I've always carried a spare derailleur "just in case" something were to happen. The 105 Di2 is a much better value! Still expensive but doable. If I do go this route is it simply a matter of taking the broken derailleur off and bolting on the new one? Is the 105 Di2 compatible with the GRX Di2?
Thanks,
