I have a 25 year old MTB with Deore derailleurs and original Shimano SIS SL MT60 lever shifters. The bike was only used for the first 5 years of it's life and stored for the last 20 years. It still has all the original cables and outers.

I'm in the process of replacing the gear cables, but the originals were fitted without any ferrules to the ends of the cables. I have bought some metal ones. The new outers are Shimano SP41. I know I should put the ferrules on the outer ends where they go into the frame stops, but should I also add ferrules to where the outers enter derailleur and shifter? Or do the entrance apertures to the derailleur and shifter act as ferrules?

10 x BIKE BRAKE & GEAR OUTER CABLE FERRULES 4mm METAL BICYCLE END CAPS | eBay

I would.

I always use ferrules where they will fit; some brifters do not use them but most of the MTB components I have run across accept them.

The way the cable enters the rear derailleur definitely needs refinement, it is entering at quite a severe angle. Optimizing the loop length and adding a ferrule would definitely improve shifting performance.

Thanks for your help. Will make sure ferrules on all outer ends.

dsbrantjr>>>>>> Thanks for the suggestion. Will definitely make sure that the curved outer where it enters the rear derailleur takes a slightly longer and gentler curve.

If the slots are tight enough that ferrules won't fit, then they weren't intended to be used there, and can't be used anyway. If there's enough room for ferrules, then they should be used. Cable housings should fit snugly into openings, one way or the other.

Me too. The more solid and square that cable housings seat, the better.