FD troubles

mjws2

Hi all!

I am having some issues fixing up a bike with a 5600 Shimano 105 groupset, running a standard compact on an FSA Gossamer crank. The problem is with shifting at the front mech; shifting is sluggish onto the big ring to the point where one has to "overshift", i.e. press the lever either beyond the point where it "clicks" and holding it there for a while or even shifting, letting go of the lever and then shifting some more and holding it there. However, doing so comes with a fair risk of the chain just dropping off the big ring towards the pedal.

The bike has seen four years of solid, all-year use, and the problem has developed slowly over that time (i.e. sudden catastrophic damage seems an unlikely cause).

Now, I and a (reasonably competent IMO) LBS tried a number of things, inc.

• playing with the cable tension and high limit screws: this was the first stop, and was attempted by both myself (several times) and the aforementioned LBS. Interestingly, putting the FD high stop into the manual-mandated setting ("set so that clearance between chain and FD outer plate is 0-0.5 mm") leads to a complete failure to shift from small ring to big ring. The FD High-limit is now closer to about 3 mm between chain and outer FD plate. I think this is why it overshifts, but the question is then: why won't it shift up when the high-limit is set correctly? (The LBS' explanation was that "the shifter is worn out" - does that make sense to anyone? It didn't to me).
• playing with the FD positioning: The FD is a band-on job, so I tried lowering and rotating it to improve alignment of the plates of the FD with the chain line/chain rings. This hasn't helped, and has proved tricky as the FD seems to have a certain element of very smooth curvature in it - I wonder, is it bent? I usually work with SRAM FDs where both plates a straight as an arrow, but then SRAM FDs are apparently renowned for being a bit pants.
• replace most of the drive train: so the bike had needed a new chain for ages, and as such we decided to replace the sprockets, chain and chainrings. Perhaps OTT, but the chain had been left on that bike for far too long. Consequently, I doubt that the issue is the result of, say, worn shifting ramps or pins.
• replace the cabling: at the same time, I replaced all cabling. Now, we can not shift with really smooth cable action!

I have a limited number of things that I can think of to try next, but would like to keep spurious expenses low so I wonder what others' thoughts are on these.
One thought was that the FD may be bent or otherwise tired. It's a reasonably cheap replacement, or maybe could even be straightened e.g. by an LBS, and would probably be my next stop. Does anyone have any thoughts on this? Could anyone show me the top-down view of what a functioning 5600 FD looks like? I will upload a photo of the one on this bike when I can get a decent camera in a bit.
Another thought was that it may be an issue with play in the BB - the MegaExo BB is a bit knackered and will want replacing soon, as some lateral play has developed, but this seems like it would make a marginal difference on shift performance.
Finally, maybe I should just move on here and hand this off to another LBS I trust, but this would strike me as admitting defeat

So before I do that - does anyone have an thoughts?

Thanks!

dj58

At four years old sounds like a combination of wear in the FD pivots and if you say you have play in your BB the chainrings could be exhibiting run-out which won't help. If I were you I'd replace the BB first followed by a new FD.

Have you taken the FD off the frame and given it a really good clean with an old tooth brush and re-lubricated it?
You say that you have fitted new cables and that you now can't achieve smooth shifts, did you replace both inner and outers, have you looked at the shifters for wear or poor cable routing?