Front Derailleur Ghost Shifting

hesker

Every now & then (maybe once or twice on a 100km spin) the front deraillleur on my bike will downshift from the big chainring to the small. It's a compact double setup. Bought the bike new in 2013. At first I thought I must be hitting the brifter by accident but it even happens when I am in the drops.

Brifters are 2011 centaur and the FD is 2010 Centaur.

I have googled this to death and can't find anything similar.

Could there be a problem with the brifter. It's almost like it occasionally can't hold the cable tension and the mechanism slips.

I'm certain it is not any of the following
- cross chaining
- frame flex
- stiff link
- derailleur adjustment. I have it adjusted pretty much spot on. Shifts are quick and precise.
- chainline
- worn chain or rings. Was happening from nearly new
- me clipping the derailleur with my foot.
- cable getting pinched or overlapping rear der cable

When the chain is on the big ring I have tried to push the FD in with my fingers and it doesn't budge.

Any ideas?

koutoubia

When the fd drifts down onto the small ring and you then throw the shifter to go back up to the big ring does the fd get pulled straight away or is there a click or two before it engages?

If it does engage striaight away I would say your shifter is starting to wear out.
Its effectively a ratchet that sits in a bevel , if you know what I mean. If the bevel is worn it may not hold the ratchet and lets go thus letting the tension go and the mech dropping to the small ring.

If you have to click one or twice then you cable has slipped.

crosstownk

Sounds like an odd problem.

I'd be inclined to suspect the shifter. Obviously something is causing a release in cable tension. If you can simply shift back to the big ring after the 'ghost shift' then it's unlikely to be a cable issue.

Would your LBS let you try a new shifter to confirm or could you borrow one from somebody?

I wouldn't like to be out of the saddle when the 'ghost shift' happens :eek:

hesker

Yeah...I know. That thought has crossed my mind. Scary.

Most of the time it drops fully, exactly like it would if I was doing the shift on purpose. And normal shifts gets it back up to the big ring. Lately sometimes I think it is just slipping down a bit but its hard to be sure.

I do have an older shifter from an 8 speed Athena group so I think it's about time I switched it out.

It's just strange that the brifter is wearing out. I'd say it had less than 2000km when it started to happen.

crosstownk

If it was my bike I'd be definitely trying the spare shifter.

koutoubia

I maybe wrong here but from the deep recesses of my tiny mind I think there was an issue with soft shifting a couple of years back with some of the shifters.
I would have to do some google-ing to see.
I believe it was a problem with the notched bevel thing.
I will see what I can dig up..

koutoubia

Ok so the soft shifting affects Centaur But its the right hand/rear shifter.
Its very possible that the mechansim that holds you cable in place is starting to unwind.

Take your shifter off the bars but leave the cable attached.
Look in at the back of the shifter. You will see a very small screw that goes through a washer. Very gently tighten this screw. This screw holds the cable and notched bevel in place.
If its not loose then the notched bevel is probably worn. Its only made of plastic.
You can get a Veloce shifter and swap the brake blade as its exactly the same.

hesker

Thanks koutoubia. I'll try that. I was going to give it a dismantle and clean but I'll try your tip first.

I think my model is actually Ultra-shift from 2009 with the carbon blade. It's hard to identify exactly which model/year.

koutoubia

No real need to dismantle as the whole mechanism is based around that screw holding everything in place. If you unscrew it and take out the washer (,easy job) you will see how it works.
If the bevel us worn I may have a spare one here.

Pinch Flat

I had similar problems with Athena shifters of a similar vintage - ended up replacing them both

Zen0

Poltergeist activity. Have your bike excorcised.

hesker

koutoubia wrote: »

No real need to dismantle as the whole mechanism is based around that screw holding everything in place. If you unscrew it and take out the washer (,easy job) you will see how it works.
If the bevel us worn I may have a spare one here.

So I checked the screws at each end of that barrel piece that goes from front to back and on which the splined pieces are mounted. They were both good and tight.

I removed the large flat spacer and the plastic piece under that looked fine(the piece which wraps the cable). I took the spring & that plastic piece out and checked the condition of the metal cog under that. That also looks like new as does the lever catch. I ended up taking the whole thing apart and it all looked fine so I re-greased it lightly and put it back together.

I found it next to impossible to re-wind that spring under the flat washer. I found a campagnolo video for a similar mechanism which suggests you need to wind the spring just over a full revolution. This is the spring that rotates the barrel when you press the thumb shifter. That got me wondering if it's possible that too high a spring tension in this could overcome the catch mechanism and be the cause of the problem.

3:50 in this video https://www.youtube.com/watch?v=K_2G5NgluQM
This is not the exact model but it's the closest I have found. My unit is Centaur Power-shift 2011. The Veloce Model from the same year looks to be the same.

So I put it back with only a short re-wind of that spring. There is still enough tension in the FD cage spring to get the thumb shifter to work properly.

The only remaining thing to check is that the cable housing is pushed all the way into the slot in the shifter. I didn't unwrap the bars so it was not possible to be completely sure it was seated all the way home but it was fairly tight so I'd be surprised this is it.

koutoubia

Certainly rewinding that spring is an acquired skill.
The front shifting system is a relatively simple thing with everything based on cable tension.
If your fd is shifting to the inner ring then the cable tension is either being released at the shifter or at the fd itself.

It is also possible that the cable is too tight or routed really badly and getting snagged.
Is it a genuine Campy cable?
I have had issues with poor shifting/braking on non genuine cables.

Where are you based?

Pinch Flat

hesker wrote: »

So I checked the screws at each end of that barrel piece that goes from front to back and on which the splined pieces are mounted. They were both good and tight.

I removed the large flat spacer and the plastic piece under that looked fine(the piece which wraps the cable). I took the spring & that plastic piece out and checked the condition of the metal cog under that. That also looks like new as does the lever catch. I ended up taking the whole thing apart and it all looked fine so I re-greased it lightly and put it back together.

I found it next to impossible to re-wind that spring under the flat washer. I found a campagnolo video for a similar mechanism which suggests you need to wind the spring just over a full revolution. This is the spring that rotates the barrel when you press the thumb shifter. That got me wondering if it's possible that too high a spring tension in this could overcome the catch mechanism and be the cause of the problem.

3:50 in this video https://www.youtube.com/watch?v=K_2G5NgluQM
This is not the exact model but it's the closest I have found. My unit is Centaur Power-shift 2011. The Veloce Model from the same year looks to be the same.

So I put it back with only a short re-wind of that spring. There is still enough tension in the FD cage spring to get the thumb shifter to work properly.

The only remaining thing to check is that the cable housing is pushed all the way into the slot in the shifter. I didn't unwrap the bars so it was not possible to be completely sure it was seated all the way home but it was fairly tight so I'd be surprised this is it.

Exact problem I had, ended up with replacement shifters. I'd get it working, but then the tension on the sping would go. It happened to me on the W200 in 2014 - that was the last straw for me.

hesker

Based in Cork.

It was a genuine Campy cable. Have fitted a non Campy cable now for the moment.

I've read that about cable tension and I can see how it might affect shifting precision but I can't see it explaining the problem here. To me it seems either the cable is getting snagged when I shift or the mechanism is slipping. But if it's getting snagged then should I not need an extra movement to complete a shift. And I don't.

Routing looks fine except I can't see what's happening where it goes through the frame between the bottom bracket & the FD. When I fitted the new cable though it went through that section fine with no snagging.

I've had a look at the price of replacement shifters and they're not so cheap.

hesker

So I took it off again yesterday evening and managed to get the spring wound the required full revolution. Took off the bar wrap and made sure the cable housing was slotted all the way home. On a 50 min commute this morning it's shifting fine even with the non campy cable, same as before.

Time will tell if the problem has magically disappeared.

Pinch Flat

hesker wrote: »

So I took it off again yesterday evening and managed to get the spring wound the required full revolution. Took off the bar wrap and made sure the cable housing was slotted all the way home. On a 50 min commute this morning it's shifting fine even with the non campy cable, same as before.

Time will tell if the problem has magically disappeared.

I hope it works out, but i found would fix mine where it would last perhaps 2 or 3 spins (it's the "Sunday" Bike). Spring would flick our mid ride, trapping me in the lower ring on the front - it was my FD that suffered from this mainly, intermittent on the back one, but I probably caught it (i.e changed both shifters) before it manifested in the back one.

borris4

I had the same problem with a Centaur Ergopower Left shifter.
I am convinced that the cable was too tight after I had renewed the cables.
Releasing the cable at the front derailleur and using less tension sorted it out.

hesker

Pinch Flat wrote: »

I hope it works out, but i found would fix mine where it would last perhaps 2 or 3 spins (it's the "Sunday" Bike). Spring would flick our mid ride, trapping me in the lower ring on the front - it was my FD that suffered from this mainly, intermittent on the back one, but I probably caught it (i.e changed both shifters) before it manifested in the back one.

I'm not sure we have exactly the same problem. I don't get trapped in the small ring at least.

When I opened mine up both ends of the spring were seated in their slots.

What did it look like when the spring flicked out on you.

hesker

borris4 wrote: »

I had the same problem with a Centaur Ergopower Left shifter.
I am convinced that the cable was too tight after I had renewed the cables.
Releasing the cable at the front derailleur and using less tension sorted it out.

I am starting to suspect this could be responsible. When I refitted it last night I was careful not to have too much tension on it. You don't need to have the cable pulled really taut in order to get it to work properly, just tight enough so there's no slop. Then again once you're on the big ring the FD cage spring largely dictates the tension I would imagine.

borris4

Wear in the shifter is less likely, the right one should show signs of wear first.
As you say there cable only needs not to have any slack in it on the small ring so that the derailleur moves without delay when changing onto the big ring.

Pinch Flat

hesker wrote: »

I'm not sure we have exactly the same problem. I don't get trapped in the small ring at least.

When I opened mine up both ends of the spring were seated in their slots.

What did it look like when the spring flicked out on you.

Mine getting stuck in the small ring was due to ghost shifting - so the shifter would shift down on the FD. Very frustrating problem.

The spring was housed behind a washer. Very difficult to get it tensioned and put back correctly - although they say campag shifters are simpler and serviceable compared to other brands, I can't see how this can be re-tensioned correctly.

Perhaps there is a special tool, but I spent many frustrating hours getting the spring re-seated, only for it to pop put again, usually mid-ride. As I said earlier, my W200 was screwed up a few years back with this problem, so it was the last straw for me.

hesker

Pinch Flat wrote: »

.....- although they say campag shifters are simpler and serviceable compared to other brands, I can't see how this can be re-tensioned correctly.

No. ..it can be done. At least providing there is not excessive wear. I had the spring out twice yesterday and although it's finicky once you have a technique that works it's not that bad. Needle nose pliers and strong fingers help.

The spring is sandwiched between the flat washer and the plastic cog so I can't see how it will pop out.

Anyway there's not much value in continuing this any further I think . I'll report back in a week or so. Hopefully might be of use to someone else.

Thanks to all who chipped in.

hesker

Well it didn't take too long. First drop was within 25 miles of fitting everything back together. It dropped again after another 15 miles.

Did the Ring of Beara at the weekend and it dropped about 4 or 5 times over 140km.

I think I've ruled out cable tension. Funny thing is each time it happened I was changing the RD at the time (this is not always the case), most times to smaller cogs but on one occasion to a bigger cog. Pretty bizarre. The cables do not overlap at any point.

I do not feel too inclined to buy another Centaur or Veloce shifter of the same design. I'll swap out to that old Athena shifter when I get a chance.

hesker

I'm resurrecting this thread as I think I finally have a fix.

The problem seems to be down to the loosening of the screw that keeps the ratchet pieces in contact with the shifter boss.

In the attached pic, the screw I'm talking about is circled in red and labelled 1.

If this gets loose it allows separation between the group of components labelled as 2 from the shifter boss 3. If it separates just enough the shifter will drop down driven by the spring tension. It obviously usually settles back into close enough contact that I can shift up again.

Recently it got so loose that I had to take it apart to reseat it all.

The fix is to apply a bit of glue on the thread ends and torque the screw down good and tight. Also that screw should be tightened first before the one at the other end of the shifter boss is tightened. This will maximise the amount of engagement between the 2 contacting pieces.

I've about 300km done since I did this so fingers crossed. Hope this helps someone else.