modern 'road' 11s setups often have a very small clearance between the rear mech and the spokes. It only takes a small nudge to bend the hanger, or a tiny bit of wear on the rear mech stop screws to have the mech tangling with the spokes in low gear. Once that has happened, it is anyone's guess whether the chicken preceded the egg or not.
Some things that don't help;
- most modern shimano mechs no longer have a curved piece on the inner cage plate that kisses the spokes first; they could, for the most part hardly be better designed to go into the spokes than they are
- modern chains want to derail off the sprockets, including the biggest sprocket. If the chain derails off the big sprocket inwards, it usually drags the RD into the spokes with it.
Some things that do help;
- using aero spokes on the DS (this gives 1 to 1.25mm more clearance)
- using a spoke protector disc
- checking the L stop screw on a regular basis (they often wear or move)
- checking that the hanger isn't bent ( preferably every time you ride the bike)
cheers
