I'm going to order a cheap 105 or kmx chain and try that 11-42
. Might be a waste of money, but will have another spare chain at the worst b/c it will be cut longer than any of my other sets would use.
Well being the generally impatient type, I decided to go ahead and use one of my spare 11sp DA chains and swapped out the 11-34 to the 11-42. Figure if it doesn't work I haven't messed up my chain since I won't have cut very much off so can still use it later on 11-34 setups still.
Changeover went pretty well... the TX RD has barely enough range for the 42, at least in stock setup. I don't have the 8-10mm gap on the big cog they recommend, closer to 4-6mm (if that) which is what Shimano typically rec's iirc. It still shifts to the 42 up/down fine, perhaps a tad slower than the other cogs, but no noise, etc. This is all on the stand, I'll give it a proper test ride later today.
B-screw is maxed, at least maxed with that little black plastic keeper nut thing, which I'm not sure is really necessary tbh. Removing it I could easily get 3-4 more turns on the b-screw. I also have a WT Road link I could put on, but would rather not unless I absolutely need it, to keep things simple. Or I could drop down to an 11-40 which I also have.
Still, I think a bit more gap would be ideal...
<EDIT> Did a quick 10km loop around the neighborhood... no issues shifting up/down on the 42. Still, when I got back I went ahead and removed that little black plastic "donut" which allowed me to get a few more turns on the screw. I put a dab of blue Loctite on it, but I don't suspect it is going anywhere. Def gives a bit more gap/breathing room, and sits on the hanger shelf fine. Still (and now realizing my CS is 48/31, not 50/36 lol), I'm not sure the use case for a 42 on the back is really there for me. North Florida US just does not have that much in the way of elevation changes. 31/42 is comically slow lol, and hard to even use unless finding a hill of some degree to plod up. But, I figure it might be useful for bikepacking off paved roads b/c of added weight, which is my Checkpoint's alter ego

.
(Before removing the "donuT")...

