So, my GRX rear mech didn't seem to like the SunRace 11 speed cassette that came with the Wahoo, even though it's supposed to be compatible. I replaced it with the same SLX 11-42 that's on the rear wheel and it's PERFECT. Since that bike is a 1x, it also gave me a little extra help on the 14-16 degree grades that try to kill me.