Currently running grx 400 on the gravel bike, maxed out with a 42 tooth cassette. That’s well beyond it’s recommended capacity, however with some tinkering it works just fine
the issue is id really like a little easier gear at the back given I’m running a 42 front that I’d like to keep. I picked up one of those 46 tooth deore cassettes for a tenner, so now need to figure out a bodge
i have one of those ‘goat link’ extender things I could try, but I expect it’ll ruin the shifting quality.
I’d ideally like to run a deore rear or similar, however have read that mtb mechs use a different pull ratio. How does that work given it’s just a spring and all the indexing happens at my shifter?
I know there is a device that alters the cable pull but not interested in going down that route
I have a grx 810 rear derailure with a wolf tooth roadlink and the shifting is OK with an 11-46t cassette and a 42t front ring
It works OK - the B screw needs winding in - which makes it a little sluggish when changing down the cassette.
I *think* GRX 400 isn't compatible with anything else so I would check before doing anything.
What I've found works well to use a 46t cassette with a 10 speed mech is a OneUp RAD cage. Unfortunately they don't sell them anymore but you might be able to find one second hand. They offset the upper jockey wheel slightly which helps it clear a bigger cassette.
From Wolftooth site -
"Shimano ST-RX400-R GRX 10 speed shift levers use a different cable pull than Shimano's 10 speed road shift levers. For proper shifting use Tanpan 11spd with a Shimano 11spd mountain rear derailleur and a 10spd cassette."
Garbaruk make a 50t derailleur cage for it (doesn't have to be purple)
Edit, sorry, just seeing you have the 400-series mech, so might not suit
GRX 812 rear mech should work with GRX400 shifter (I believe it uses the same cable pull as Tiagra 4700 10sp, which is the same as 11sp GRX).
That mech is rated to 42t rear, but people on here have reported it works with 46t.
This is assuming you're riding with a single ring crankset?