Ah, had a quite reread, this the modern XT mech M771?
That's probably more try to life when things had to be more accurate.
Forget the B-tension, it designed for tweaking to the top cog to get a close as possible for the best shifting. There is only so much distance it can make.
Everything you do to distance from the top cogs makes everything worse for every other cog, especially the smaller cogs.
What does 'try to life' mean?
I have been working on it again today. I did manage some more clearance by doing the reverse b-screw trick. I actually found a couple of even longer bolts/screws which fit that thread in the garage. I tried one much longer than the original but it actually doesn't provide any benefit past a certain point as the extra length just goes beyond where the little lip catches the screw so length then becomes moot.
I had better improvement by taking the derailleur off and screwing the original in the other way. The got me a bit more clearance.
There is still the little rattle but only on the lowest gear. I went for a ride and the functionality does not seem to suffer.
When I got it back and lifted the wheel and pedaled I noticed there is no sign of trouble when it is going that direction. That rattle only happens when reverse pedaling and how often will that happen when riding? Almost never. I also do not see any issues when free wheeling either. So I may just let sleeping dogs lie with that.
On the other hand I have been having a terrible time trying to get the gears to index. They weren't right even before adding this new cassette but the issue then was that it is a 9 speed shifter and the old cassette was 8 speed.
Now with this new one, it is a lot better, in that I can change to all gears but I am unable to get proper indexing for all gears. Was trying for hours and still could not get it right. I can either have indexed low gears and jumping or unusable bottom gear or two or vice versa. I was fiddling with the adjuster for so long with tiny increments and could find no way for them all to be right. It will either be a shade too tight for low gearing to work and they jump around or a shade too slack and am unable to shift out of highest gear without double clicking or when shifting into higher gears several jumps at a time.
I was able to fine tune it so that everything seemed right for the 32t chainring but then when I shifted to the 20t the low gears were out again. That meant I had to slacken the wire a bit for them to work and then the high gears would be out. I, of course, chose indexed low gears for now as those are the ones I use most.
Not sure of a way around that? Made me suddenly want to say screw it and get thumb shifters! If I don't find a remedy that may well be what I do as indexed shifting is more trouble than it is worth if I don't find a way to fix it.
With all that said the lower gearing is great! 14 gear inches feels just about right! I also had more to play with on the middle ring. I didn't have to go into the lowest much on that little ride out but felt I had plenty more in reserve with those 2 extra low gears of 32 and 36. Haven't had chance to try on the meaner hills yet.
