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Chorus front derailleur question
 

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KerryIrons
Joined: 12 Jan 2004
Posts: 2935
Location: Midland, MI

1/17/18 1:52 PM

Chorus front derailleur question

I've got a Campy Chorus front derailleur and there's a piece of it I don't understand. On the top of the main body, there's a threaded hole that is used to hold the bolt that holds a little finger that is curved and can be moved so it touches the seat tube. The finger points to the rear of the bike. I cannot understand what the purpose of this thing is. In the constant quest for light weight, a steel bolt and a little piece of aluminum that serve no purpose . . .

Enlighten me!

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Sparky
Joined: 08 Dec 2003
Posts: 16793
Location: Portland, OR

1/17/18 2:14 PM

It is a stop so it does not flex in more 'in' than it moves the chain 'out' I believe.

The Di2 stuff has this and comes with a little metal pad you stick on the carbon so as to not poke a hole in it.

I may have an extra one of those if you are in carbon crisis for the stop. ;)

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dddd
Joined: 11 Jan 2004
Posts: 3234
Location: NorCal

1/17/18 3:32 PM

Yep, Shimano uses a simpler set screw, but always there is adjustment for the myriad shapes of "brazed-on" styles of mounting and for the multitude of seattube shapes and sizes.

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KerryIrons
Joined: 12 Jan 2004
Posts: 2935
Location: Midland, MI

1/19/18 8:01 AM

Thanks. I'll have to look at how it is positioned to better understand this. I thought it was to somehow brace against the seat tube. With a Ti frame I have no worries about carbon crises.

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 4177
Location: Nashua, NH

1/21/18 10:28 AM

It IS supposed to brace against the seat tube

Perhaps it's installed incorrectly?

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KerryIrons
Joined: 12 Jan 2004
Posts: 2935
Location: Midland, MI

1/22/18 3:37 PM

Bracing

I do have it against the seat tube, just as it was installed on the unit when I bought it. I'm having a hard time seeing how it really has any effect to stiffen the derailleur.

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Sparky
Joined: 08 Dec 2003
Posts: 16793
Location: Portland, OR

1/22/18 4:03 PM

"I'm having a hard time seeing how it really has any effect to stiffen the derailleur."

Think in the case of a carbon braze-on and not a steel or Titanium welded metal one. Or a riveted on braze on before we had Di2 FD forces in play.

On my Addict, I JB welded a thin metal piece shaped to the braze on well onto the seat tube when I put Di2 on it when I saw this picture:



My rube also acts as a stop for the screw of which you ask, and stiffened the front shifting up really nice. As in when I pulled the Di2 and put 5800 on it with cable pull.

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