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I am having a world of trouble trying to get my FD aligned properly and shifting properly from small to large cog and back again, especially when riding up hills.

When on the flat, they change fine, but when I apply force on the pedals at a sprint or when going up hills, the chain won't shift from large cog to small. Obviously I am in a pain trying to pedal up a hill on a 52T cog! Yet on the bike stand everything looks and performs fine.

Could it be that by the force of my effort to pedal harder, I am actually "bending the bike" to the right (crank cogs on the right) slightly, which in-turn increases the gap between the chain and the outside FD cage from touching the chain to force it off the big cog? It's the only explanation I can come up with. Or maybe my cranks are bent? Or my FD is bent?

Looking from above, there is a slight gap increase to the rear of the FD as compared with the front closer to the center of the crank. But very, very slight.

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    In general, you cannot shift a derailleur bike when under full load. Indexed shifting helps with shifting to a larger gear (making it possible to shift under partial load), but does little for shifting to smaller gears. – Daniel R Hicks Jun 25 '18 at 12:10
  • @DanielRHicks where did you get that? My bike has been able to down and upshift under load for over 6000kms. Suddenly it doesn't so it's really an issue with the drivetrain either the chain has stretched, the brazeon has bent or the derailuer has bent... anyway I now have the info I need to investigate. Thanks – Fandango68 Jun 26 '18 at 6:30
  • I said "under full load". But, of course, this could be a simple matter of cable adjustment, or your cable could be rusted and sticking. – Daniel R Hicks Jun 26 '18 at 12:18
  • What's full load dude? – Fandango68 Jun 27 '18 at 2:43
  • When you're cranking hard. Generally will be the case while climbing, unless you make a conscious effort to ease off for a few seconds. – Daniel R Hicks Jun 27 '18 at 12:11
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I have the same model front derailleur and have experienced the same issue.

It is unlikely that the bike is bending enough under pedalling force to cause this (unless the frame is broken or cracked). More likely it is a problem with the front derailleur, and the extra chain tension from pedalling hard exacerbates it.

Now, obviously if there is damage such as a bent front derailleur cage then this could affect the shifting. But if the problem has just started happening from normal use, without the bike being involved in any recent crashes or mishaps, then you probably just need to service your derailleur.

The manual has a section on maintenance that if followed should resolve the problem. Here are the main points along with some of my own observations:

  • Check the derailleur is clean and moves freely. When I suffered this problem there was grit in the moving parts, preventing the cage from moving all the way to the lower lower stop when downshifting. One way to verify the smooth action of the mechanism is set the derailleur to the small chainring and carefully pull at the cage with your fingers. It should move smoothly, with the spring pulling back quite firmly against you towards the seatpost. I find spray lubricant (e.g WD-40) to be very effective at displacing grit and freeing the mechanism, followed by a drop of oil at each pivot and some grease on the spring to keep it lubricated.

  • Check the shifter cable tension. Excessive tension can prevent the derailleur from sitting tight against the lower stop.

  • Ensure the derailleur is correctly aligned. You mention that there is an “increase in gap” at the rear.. I can't gauge how significant this is without seeing it, but the manual does state that the outside of the cage must be parallel to the chainrings. If it is too far out of alignment it can definitely affect the shifting. Also check the vertical alignment: the gap between the large chainring teeth and the cage should be 1.5mm to 3.0mm.

  • Check the adjustment of the lower limit screw. With the chain on the small chainring and largest sprocket, there should be a 0.5mm gap between the chain and inner face of the FD cage. I find it is best to do this with a bit of tension in the chain, as sag in the chain affects the size of the gap there.

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    I will note that there is an art to adjusting the "twist" of a FD on the seat tube. It's generally the case that the optimal position is not exactly in parallel with the chainrings. (And, of course, there's also that fussy up/down adjustment.) – Daniel R Hicks Jun 25 '18 at 17:45
  • @clubdog Thanks for that PDF link. It has everything I need to know and check and yes, my version is Braze on and it looks like the braze itself is bent, hence the increasing gap between chain-ring and outside cage. I'll follow the manual and report back asap. – Fandango68 Jun 26 '18 at 6:28
  • Well it turned out to be a problem with the cable, the cable housing and the FD itself. I took everything apart, cleaned, oiled and put it back using Campag's recommended videos, etc. The FD braze-on was ok, as it should be, as it's a pretty thick piece of steel! The issue was the FD screw and threading had been worn. I replaced the screw and had the thread re-tapered. I aligned the FD using a card to have it parallel with the chain ring, and re-did the cabling with a new gear set. It all has worked like a charm now and shifts beautifully. Thanks – Fandango68 Jul 9 '18 at 4:42

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