Campy Chorus 12 front derailleur issue

[zap]

Upgrading one of our tandems (this one with 145 rear spacing) to Chorus 12 and new FSA SLK MegaEvo double crankset.

Ran into an issue yesterday with the Chorus front derailleur. Notice that the derailleur would not move out nearly enough for a chain to clear the cage when in the big ring. Ok, unscrew the high/outer limit screw and that will fix that.

Nope, no change. Discovered that the high/outer "ramp" touches the derailleur body and never makes contact with the limit screw even when its screwed in as far as it can go.

This limits how far the derailleur cage moves out......and the high/outer limit screw having no impact at all.

Suggestions?

[Dave]

If I understand correctly, the lower ear is for the high limit and hits the area just behind the limit screw, before it contacts the screw. In this picture, the screw is not protruding very much, but the low limit screw is showing a lot of threads.

This would appear to be a manufacturing problem. I'd order another and send the other one back. The 12 speed FD does set up differently than some older models. The big ring limit screw limits the over travel required to make the shift to the big ring, but the derailleur moves back in a bit, as soon as the lever is released, so it's not resting on the high limit screw.

[zap]

In the picture the high/outer limit screw is in as far as it can go. The corner of outer "ear" closest to the mounting screw hits the inside radius of the derailleur body.

The fact that this derailleur will not work with my tandems chainline is an issue that I will have to resolve separately. Most likely a tandem specific clamp that moves the derailleur out by 6mm.

[oldpotatoe]

If I understand correctly, the lower ear is for the high limit and hits the area just behind the limit screw, before it contacts the screw. In this picture, the screw is not protruding very much, but the low limit screw is showing a lot of threads.

This would appear to be a manufacturing problem. I'd order another and send the other one back. The 12 speed FD does set up differently than some older models. The big ring limit screw limits the over travel required to make the shift to the big ring, but the derailleur moves back in a bit, as soon as the lever is released, so it's not resting on the high limit screw.

I would agree, the fder pivots hitting the body before the screw hits the limit 'ramp'..You could try another, non-12s front der also..just about any front der 'should' work.

BUT, the other gig is the starting point for the front der..the chain needs to be REALLY close to the inner fder cage, and the cable needs to be REALLY tight, when on small ring and biggest cog in rear.

[ultraman6970]

Hi, 12 fd is set up like the 11 fd??? 11 chorus I remember is set up pretty much by cable tension not like 10. What happens if you lose that screw all the way back??? the FD works?

[zap]

I set up Campagnolo 10 and 11 front derailleurs the same way. Determine the proper inner position with the low limit screw then adjust the screw one full turn to lower the cable attachment point, tighten the derailleur cable (while pulling the cable somewhat tight) then turn the screw back that one turn. The result is that the cable is good and tight so when you move the shift lever, the derailleur moves right away and all other shift points are spot on.

Once I get this 12 f. der. sorted I will report back.

[thirdgenbird]

I set 10spd up using the exact method. Interested to hear what you learn on 12. I’ve got a group on the way.

[zap]

Well, it appears the threaded portion for the high screw is machined off center. The head of the supplied screw hits the top of body preventing the screw from threading in further.

I grabbed one of my adjusting screws from an old Record 10 f. der. that is longer and viola, goes through the bottom of the body.

Still puzzled by the lack of throw.....will not work with my tandems chainline even with a 6mm extender clamp. Doubt this derailleur will work with any bike with a 135 or wider rear axle spacing.

[Dave]

Campy has a video on the setup. It's a lot easier with a frame mounted or inline tension adjuster. The shift levers come with an inline adjuster. My current frames have no adjuster, so I installed the inline adjuster. It makes the job easier.

The high limit screw is still important. Without it, you could push the chain off the big ring. The limiting ear just doesn't rest on it, after the shift lever is released.

The tension has to be set so the trim click for the little ring moves the cage slightly further to the left, to eliminate chain rub in largest two sprockets. To shift to the little ring, push the thumb button all the way down. After it's released, one more click becomes available.

[binouye]

Co-motion makes a FD clamp that holds a braze-on der out a couple mm further away from the tube than normal spec, for better shifting with the wider centerline for 145 rear spacing. I have an extra one, PM me if you're interested (but check your seat tube diameter first, as the newer Co-motion tandems use pretty big tubes). FWIW, I'm now using an older XTR FD on the tandem, which works fine with Chorus 11 ergos and 54-34.