Rebuild -Front derailleur advice needed

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fausto99
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Rebuild -Front derailleur advice needed

Post by fausto99 »

I have just fitted the bb, crankset and fd (no cables yet) to my refinished frame and it looks like this:

Image Image Image

The back end of the fd looks too far away from the 50 chainwheel. I don't remember it looking like that when I dismantled the bike and I hadn't had any problems with front shifts. The fd does not look damaged or bent, so, is it OK to preceed? Should I attempt to bend the fd? Any thoughts gratefully received.
MikeF
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Re: Rebuild -Front derailleur advice needed

Post by MikeF »

Presumably it must be the same if you haven't changed components. Can the FD go a little lower on the seat tube? It only needs to just clear the front chain ring.
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531colin
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Re: Rebuild -Front derailleur advice needed

Post by 531colin »

It does look wrong.
If its a front mech. for brazed-on fittings with a separate band, they can be mis-assembled somehow.
If the band is part of the mech, its hard to see how it can be mis-assembled?
Don't bend it unless you're sure!
edit....the parallelogram is lined up with the seat tube.....should it be at an angle to the seat tube?
Last edited by 531colin on 5 Sep 2017, 5:11pm, edited 1 time in total.
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fausto99
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Re: Rebuild -Front derailleur advice needed

Post by fausto99 »

MikeF wrote:Can the FD go a little lower on the seat tube? It only needs to just clear the front chain ring.

It is just clearing at the front - just a shade less than 1.5mm to the tip of the chainring tooth. I wouldn't like to go closer than that.
Last edited by fausto99 on 5 Sep 2017, 5:11pm, edited 1 time in total.
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fausto99
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Re: Rebuild -Front derailleur advice needed

Post by fausto99 »

531colin wrote:It does look wrong.
If its a front mech. for brazed-on fittings with a separate band, they can be mis-assembled somehow.
If the band is part of the mech, its hard to see how it can be mis-assembled?
Don't bend it unless you're sure!

It is a 1996 Campag Veloce with integral band. The frame has no braze on for a fd.
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Re: Rebuild -Front derailleur advice needed

Post by Brucey »

I have (in desperation) bent FDs before now but the cages are made of hard steel that sometimes breaks instead of bends......

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531colin
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Re: Rebuild -Front derailleur advice needed

Post by 531colin »

You need somebody really familiar with that mech.....and it isn't me.....sorry.
gloomyandy
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Re: Rebuild -Front derailleur advice needed

Post by gloomyandy »

Do you have any photos of how it used to look?
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Spinners
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Re: Rebuild -Front derailleur advice needed

Post by Spinners »

It's a front mech designed for the then standard 53 tooth outer chainring so on your 50 tooth compact outer chainring you'll get such gapping as the circumference 'bend' is tighter.
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531colin
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Re: Rebuild -Front derailleur advice needed

Post by 531colin »

Whats the difference in radius between 50 and 53 teeth?...my guess would be a few millimetres, but my bet would be Brucey will know!
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Mick F
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Re: Rebuild -Front derailleur advice needed

Post by Mick F »

In my experience, Campag front mechs have the same profile on the front face. the back face is different for triples vs doubles.

This one is mine.
Campag Comp Triple with a 53t chainring and works perfectly ............ and always has done.
IMG_0180.JPG
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Brucey
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Re: Rebuild -Front derailleur advice needed

Post by Brucey »

531colin wrote:Whats the difference in radius between 50 and 53 teeth?...my guess would be a few millimetres, but my bet would be Brucey will know!


difference in radius is about 6mm I think.

FWIW I don't especially like the look of Mick's mech (is it meant to run OK with a ~65T chainring...? :wink: ) and I would adjust the (Braze-On converted to band-on type) mounting accordingly. OP doesn't have that option.

Maybe it has always been like that and it has always worked OK, but it doesn't look right. IME mechs that look like that (tail high) sometimes

a) fail to lift the chain well because the inner plate is not low enough
b) allow the chain to get between the outer side plate and the chainring, which causes a jam.

But if it works it works; "C’est brutal, mais ça marche" indeed....

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gaz
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Re: Rebuild -Front derailleur advice needed

Post by gaz »

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Mick F
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Re: Rebuild -Front derailleur advice needed

Post by Mick F »

I wonder that the issue with these mechs, is the variation in seat tube angle?
My Mercian is steep ....... or some would say that ....... at 73deg.
Maybe at 72deg or even less, the tail height would be better?

I know that my Moulton has had some tweaking with respect to the front mech height, and that the front mech is a Tiagra, but it has a similar tail height even though the big ring is 61t.
It sits a bit too far back with the Ferrit Worrier adaptor, but it changes fine.
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Re: Rebuild -Front derailleur advice needed

Post by fastpedaller »

I'm pretty sure seat tube angle wouldn't make a difference - just thinking if you rotate it with the bb as the centre, the distance from the chainring is the same, but the seat tube angle changes ....... If that makes sense. Always makes me wonder how those oval chainring set-ups work with double clangers?
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