Originally Posted by
Chilepines
I've got a GRX 815 di2 RD running a 10-42 cassette with a RoadLink DM. I think you need either that, or the GoatLink for your GRX 400 - but it is not clear from the Wolf Tooth site what you need for that derailleur. Works well on my setup, which happens to be on a tandem with a 46/30 crank.
Great to hear RoadLink DM works with your 2x GRX group. I'm on 10 speed GRX 400 also with 46-30 up front. The WolfTooth website is't very clear. My impression was RoadLink DM was for 2x groups with a chain tensioner, which GRX has. Your setup confirms RoadLink DM is what I should go with.
Did you change the chain to a longer one when you went to RoadLink DM with your extra wide 11-42 cassette?