Rear derailleur shifting issues

Drollic · 26 Aug 2018 at 11:26

I'm literally lost as to why my ultegra 6800 rear derailleur won't shift properly unless there's an issue on the internal cable or at the hood on the levers. I noticed the bike not shifting quite as it should just the other day on a ride. Very minor almost half misshifts occasionally. Yesterday and the bike wouldn't even shift into all gears despite nothing changing - no knocks or it being bent etc. Cable is probably 18 months old, stock and has about 3300 miles on it.

Tension issue due to stretch I thought. Shifted into smallest cog, and undid the cable bolt. Made sure derailleur shifted by hand into all gears. It does. It correctly goes into smallest cog by itself as well with no tension. Made sure limit screws set correctly. I turned back in the rear barrel adjuster leaving room either way and reattached the cable a fraction tighter. Despite this, and no matter where the cable is attached, or what I do with the barrel adjuster, the derailleur either won't shift into the biggest cog or the smallest cog. It's as if when the cable is too tight, it won't reach smallest and when loose, it won't reach biggest cogs leaving me with 8-9 gears at the rear instead of 11. When you try and press in the levers to reach these gears they just almost move freely. should have gone di2. Any ideas?

Lethal` · 26 Aug 2018 at 15:31

That's a fair old time for an inner cable in a 6800 system. I'm finding that the shifters eventually chew the cable so I'm lucky to get 3500 miles out of a cable. Anyway, I'd certainly be looking to replace the cable and housing. It sounds like something is in the system causing it to stick - or maybe it is partially frayed already somewhere.

Jonny ///M · 26 Aug 2018 at 17:10

Will either be a build up of the fluffy coating of the inner cable inside the inner straw guides of the frame, general corrosion or if you pull the hood back you will see the cable will be fraying no doubt.

mattyfez · 26 Aug 2018 at 21:43

As above .. A sticky cable is the obvious thing to check, sounds like it's new cable & outer time.

Just a normal service job that needs to be done now and then like a worn cassette or chain..

Drollic · 26 Aug 2018 at 22:27

Have I expected too much at around that mileage? If so, I'll look to change up at 2.5k. There is a buildup of the fluffy coating around the bolt holding the tension, or was anyway.

mattyfez · 26 Aug 2018 at 22:36

Drollic said:
Have I expected too much at around that mileage?

Not nessesarily.. But probably.
Cables and outers are a service item and do need to be replaced occasionally.

Sooner or later they will get gunked up or frayed, three thousand miles is a good innings by any stretch of the imagination.

And they are very cheap to replace.

Lethal` · 26 Aug 2018 at 23:02

I just this Monday thought "Hmm.. My shifting seems a bit laggy and something is off. I should change it today." (having had awkward to find cable ends snapped off inside shifter 3+ times).... later on... nah can't be bothered. Wednesday ride out... cable perishes enough part way through ride that I can't get into the 13/12/11 sprockets and I return to find it pretty damn frayed and making a mess of the shifter. Eventually extracted it and the cable end with some tweezers etc. Moral of the story is I should have listened to myself on Monday...