I’m having a strange issue on my shifter for the front chain ring.
It has moments where it does not change to the small ring no matter how many times I push the small paddle. I figured I needed to tighten the cable so set it aside for the weekend. When I got around to fixing, it was suddenly working fine again. I have had this issue intermittently in the past.
I realise the shifter is getting on in age, but would anyone have any ideas about the possible issue? I don’t ride competitively and can’t really justify dropping coin on new gear. I’m already looking at a hub replacement and wheel rebuild on my old rear Zipp so watching pennies.
The drop to the small ring is when there is no (or shouldn’t be) tension in the cable, it’s pulled back by the spring in the front mech. So it if happens again, and assuming with 7800 then there is some visible cable near the mech, you should be able to check to see if it is the cable that has tension in it (ie cable fray/cable liner frayed/binding/shifter itself stiff from dirt) or if it’s the spring that’s for some reason not moving - the cable will be loose - and in that case (there’s some dirt/stone in the spring or mech. In the latter then a good clean of the mech itself should sort it).
I wore out a front shifter and it did this same thing, needed to change up and then change down rapidly. A dissasembly of the shifter and clean helped for a bit, but was the start of the end as it came back soon after. But unless you ride somewhere very odd, then you’re never going to wear out the front mech before the back one. And this was on a 9sp ultegra that took about 10 years of 400km/week riding in a coastal climate to get to that stage.
I’ve noticed that when applying a little pressure to move the small paddle towards the front of the bike it increases the odds of ‘engaging’ and then dropping it down to the small ring.
It really does seem like it’s something to do with the way the small paddle catches.
Still suggest the check above, and then further to that you should be able to trace where the sticky cable is - in frame, through bars, in shifter mech. Don’t forget that the cable is still pulled by the front mech spring, there’s nothing in the shifter or anywhere else that pulls the cable if the mech isn’t doing it.
But in this case then a blast with an aircan to see if there’s anything sticking in the shifter may be worthwhile too. And if the shifter is still playing up, and you are the point of considering a swap, then whilst perhaps slightly questionable you’ve nothing to lose by upping that to a spray with isopropyl (through one of the ‘straw’ cans). See if that sorts it. If it does then you can re-lube.
If it’s not the cable, it’s probably petrified lube. The original grease in those is kind of famous for turning solid over time, and that can cause the lever (s) to fail to engage. Spray the ever loving crap out of the internals with a degreaser like Clean Streak, let it sit for a while. Follow with a rinse of WD 40 or similar, then (if you can) blow them out with compressed air, finally douse the internals with a persistent lube like Boeshield.
Excellent.
Definitely make sure to add some lube to them, the WD40 isn’t sufficient, and they’ll eventually self destruct without something more in there. Boeshield works surprisingly well.
That Boeshield was the missing bit for me - I worked out all the other bits. I’ve started to use lock lubricant (designed for keeping key locks working smoothly, and magic for my motorbike ignition and panier locks). It’s the same type of applicator as WD-40 but seems to last pretty well on small mechanical parts ie mechs, of my older bikes/commuters.