Front Mech headache

GoatBeard

Regular
Looking for some help setting up my front mech, my god how I wish it was easier. With the brifter slackened / set to the small ring, I can loosen my cable just enough to get the hanger cage to not rub. I can then set the limit screw so there's some slight movement in either direction but little / none in the direction of the frame. However, it won't make the the shift up to the big ring like this. Pulling the cable harder doesn't help. The only way is by setting the limit screw to rub hard on the chain.

Also, on the front mech cable I've just installed a Jagwire inline barrel adjuster. This sits between two outers with ferrules. Twisting the barrel adjuster doesn't seem to have any impact at all on the mech.

Lastly, I'm noticing some stress cracking on the bracket that holds the front mech on to the frame. It's carbon fibre so I'm a bit worried about that. Hopefully it's just the paint some of which has chipped off.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
Always have the front mech cable tight in the bottom gear - easy to achieve as you can use a tyre lever or screw driver to push the mech away from the frame and nip up the cable bolt. Is the High limit screw wound out far enough to shift up
 

Ajax Bay

Guru
Location
East Devon
I can then set the limit screw so there's some slight movement in either direction
You're talking about the lower limit screw here (but vice versa this applies to the higher limit one as well).
The limit screw sets a limit; one way - in this case it prevents the FD cage from moving in the direction of the frame. There should be 'loadsa' movement towards the large ring, pushing it by hand, say.
So you need NO movement in one direction and lots of scope for movement the other way. This not "slight movement in either direction".
As for tension: what @fossyant says.
 
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Nibor

Bewildered
Location
Accrington
Always have the front mech cable tight in the bottom gear - easy to achieve as you can use a tyre lever or screw driver to push the mech away from the frame and nip up the cable bolt. Is the High limit screw wound out far enough to shift up
^^^This^^^
 
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GoatBeard

Regular
Oh yes. There's enough movement in the high limit screw to make the shift up I normally wind it out completely and then wind it back up when I'm done. Where I'm struggling is getting the cable to not rub and still make the shift. Even tried levering the mech away from the frame and then fastening the cable, too. Same issue. Then there's the Jagwire inline barrel adjuster that doesn't seem to tension against anything?
 
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GoatBeard

Regular

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GoatBeard

Regular
Slight cracking going on where the bracket rivets on to the carbon frame...pictures
 

Ajax Bay

Guru
Location
East Devon
The 'braze on' (of course it's not brazed on, but let's move on) is either able to cope with the force that the cable is applying to the FD arm, or it's not. It'll either rip off or it won't. Don't blame that. Picture of FD from the side, with the chain on the large ring please.
 
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faster

Senior Member
Just waiting for this! Sorry - I have already been through this and I had no problems getting my old Claris bike's front spot on. Now, as for Ultrgra. Anyway, I'm wondering if this might be an issue...
I would say that is your problem, and even if it's not, it needs to be fixed. That braze on looks like a bit has broken off, and the top rivit in the second photo, which should be holding the braze on to the frame, looks like it is under it rather than on top.

It's probably difficult to find a new braze on. If it was my bike, I'd drill that top rivit out and try to rivit it back on with a small washer around the rivit, which will hopefully hold it to the frame securely.
 
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GoatBeard

Regular
I think my problem might have been staring right at me. Does this cable routing look okay? Seems that the mech is catching on to the wire when I shift up to my big rear cog. When I manually push the the mech it overcomes the force of the cable there and no chain rub...Trouble is I can't see any alternative ways to route the cable.
 

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Ajax Bay

Guru
Location
East Devon
Your images are really clear, but allow me to observe that it'd be a lot easier to see everything if:
1) You stopped turning the bike upside down (Rule whateveritis)
2) Provide an image which shows the setup from the side so we can see the cage, as well as one from the rear.
 

Globalti

Legendary Member
The routing is correct but looking at that picture the right way up (!) you can see clearly how the cable pulls initially at a big disadvantage meaning the tension is extremely high, especially when you are pushing a lever about 4" long when that arm is only 1" long. In that case the derailleur has to be absolutely rigidly mounted to the frame and if it isn't it will just move, reducing the efficiency of the movement. Several contributors to this thread suspect it's moving and the condition of the mounting plate and rivets tells me they could be right - that bottom rivet appears to be doing nothing as the plate has broken away. What do you see happening when you put tension on the cable? I bet the bracket is moving away from the frame, which explains why the lever isn't moving the cage far enough to derail the chain.

What is the diameter of the tube? You might be able to get a clamp-on derailleur that fits, even with a bit of shimming. Alternatively drill out the rivets, clean everything up and remove all paint then glue the bracket to the frame using Araldite - you've nothing to lose.
 
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