Shimano Shadow RD-592 SGS rear derail on 36
 

I am trying to run a triple up front with a 36 large cog in the back. Using a Deore Shadow 592 SGS rear derailleur. I assume you just use the usual technique to determine chain length (big/big plus a link). In my haste I just used all 116 links, never been a problem on my touring triples in the past. Now it seems a bit fussy (rear der cog grinding in 36). B screw is in all the way. I have found very little info online as to the preferred position of the "second pivot" of the Shadow derail, seems like straight back from the mount is preferred. Shimano's diagram shows it straight back. Nor have I seen a new way to determine chain length. I don't happen to have another chain pin, so tomorrow will be the day for me to sort this out. Anyone ACTUALLY RUNNING A 36 WITH THIS REAR DERAILLEUR? School me.

I run a 12-36 with my 592. 50/34 double up front. I've not had issues clearing the 36. What's your spread up front?

Rear der max cog capacity is also controlled by the der hanger length. Back in the day when horizontal slots were the standard one could change this dimension by moving the wheel forward or back in the slots to get the guide pulley to cleat the cog underside. With today's many vertical dropouts this is no longer possible (although I have seen slight hanger length differences between OEM and aftermarket hangers that fit the same bike).

I also like the rear der cage designs that place the guide pulley off center from the cage pivot. This allows the guide pulley to raise or fall WRT the cogs as the cage plays out or takes up chain slack. The bigger the cog the more the pulley drops giving room for that cog. The 591 ders (and most all previous Shimano ones for decades) have this design. With the guide pulley and the cage pivot on the same axis the chain length no longer influences the pulley/cog gap.

So my suggestion is to not use the 592 version. Andy

Since you haven't provided any info about your chainring sizes...who knows? Shimano spec is 22t difference between small and large rings, total capacity is 45t. If you are within spec the proper way to size the chain is small/small.

Chainrings are 24 38 48. I know I'm over capacity up front, which I have never paid attention to in the past. Now it is an issue with the over maxed out drivetrain. I have a different 12-34 cassette, but I'm really wanting the lowest practical gearing. I always thought Shimano was conservative in their guidelines, guess not so much here. I don't see how the small/small would give you the proper length if running a big spread. I never use the smaller 6 or 7 cogs of the cassette in the small ring, so I have been able to get away with just running the full length chain in the past.

Thanks for this, I had a XT Shadow rear derailleur a drop bar bike (Fargo) with a double up front and it worked great, thus my choice of rear mech. Newer is always better, just check out the road forum *smiley face emoji*.

As I said if you're within spec small/small gives you the longest safe chain length. This results in the smoothest running drive train with no sag in the small/small. If you're within spec.

I've pushed the shadow version of the Deore to 40t a couple times. 36 is actually not too much of a stretch, burying the B-screw does it most of the time.