Originally Posted by
thadoggfather
Hey guys anybody put a larger cassette on a GRX 815 Di2 than 11-34? according to shimano largest supported is exactly that, but then I read this a post on GRX (dammit can't link it yet) it says you might be able to go bigger depending on your bike.
I have a canyon grail CF SL8
I run an 11-42 xt cassette with a GRX 815 RD with 48/31 chainrings without the need for a roadlink. Zero shifting issues in any gears. Proper chain length and b-screw adjustments took some trial and error but overall I wouldn't hesitate to do it again. I originally had an 817 RD installed but the 815 handles the bigger cassette in a 2x configuration much better. The only thing I would do differently is to get the lighter XTR 11-40 cassette, the xt cassette being a few grams heavier isn't a deal breaker for me though.