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PostPosted: Tue Aug 07, 2012 9:00 am 
Retro Guru

Joined: Tue Dec 21, 2010 6:31 pm
Posts: 1112
Hello,

I've set up a steel framed bike with 9 speed campagnolo veloce
to try to get my girlfriend into road cycling.

I've been having persistent problems with the chain coming off
the small chainring at the front. It seems to happen mostly when back
pedalling and sometimes when changing gear (I know some people
say you just shouldn't back pedal, but getting my g/f out of the habit is
not easy).

I noticed that the bottom bracket spindle is quite long (113mm, square taper). The chain line from the small ring to the big sprocket and second biggest sprocket is quite steep. Is this the most likely reason for the chain problem? Or is there some simpler solution that doesn't involve replacing the BB? It's an Italian thread BB and they aren't that easy to find here.
Also, there's not room to adjust the chainline by moving the rear hub.

Cheers,

Johnny


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PostPosted: Tue Aug 07, 2012 9:11 am 
Retro Guru

Joined: Tue Dec 20, 2011 2:49 pm
Posts: 276
Is the front a double or a triple?

It sounds like you have used a double chainset on a triple BB (IIRC a double should have a 108 or 105mm BB, 113mm being for triples)

Unfortunately it sounds like you do need to change the BB, maybe someone on here has one in their parts box they could let you have cheapish? Try posting in the wanted section.


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PostPosted: Tue Aug 07, 2012 9:14 am 
Retro Guru

Joined: Tue Jun 03, 2008 4:31 pm
Posts: 741
Wind the stop screw in until the front mech only just misses the cahin in first gear. If you can do that then I would suspect the BB.


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PostPosted: Tue Aug 07, 2012 11:13 am 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 8222
Location: New Forest, UK
This is a persistent problem on most small road bikes - the short stays give a very steep exit angle from the chain ring for bottom gear.

As said, adjust the front mech as far as you dare, but the best way is to pedal back as little as possible. :D You can also train her to shift the front up and reseat the chain bay pedalling forwards gently.


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PostPosted: Tue Aug 07, 2012 12:00 pm 
Retro Guru

Joined: Tue Dec 21, 2010 6:31 pm
Posts: 1112
Thanks gents, I will give these a go.

She's getting used to shifting with the ergopower levers, so we have a system
where she shouts 'Down!' or 'Up!' and I have to shout back 'Left lever!' or 'Right ear!'. I really hope she picks up shifting soon :roll:


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PostPosted: Tue Aug 07, 2012 12:54 pm 
rBoTM Winner
rBoTM Winner
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Joined: Tue Mar 27, 2012 9:28 pm
Posts: 3104
Location: Mansfield Woodhouse, Nott's.
Maybe nothing to do with your problem but.....

I've got Campag' ergopower levers on my Wilier and if i shift too quickly from the big ring to the little ring,
it misses the small ring completely and drops on the bottom bracket, i now shift slowly and it drops on the small ring everytime.

Also had the chain drop completely off the small ring when i've had the rear mech/chain on the second big gear cog and on the big ring,
then changing down from the big to little ring it misses and drops off, changing slowly with ergopower levers is a must for me.

On many modern bikes these days and the vast amount of gears they have the chain deflection
is massive to the point a little clamp on device has been made which is called a 'chain watcher'
https://www.google.co.uk/search?num=10& ... LVyhUdbBIo


Ian.


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 Post subject: tweaks
PostPosted: Tue Aug 07, 2012 7:24 pm 
rBoTM Winner
rBoTM Winner
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Joined: Mon Aug 08, 2011 5:58 pm
Posts: 162
Location: Scotland
Its sometimes possible to 'tweak' (as in with a pair of pliers) the front mech cage to give a positive downward shift whilst not having to have the adjuster screw quite so unwound (therefore causing the chain to come off). Things are a bit desperate by the time it gets to this, but it's been known to work! Suspect a shorter BB axle will help, as will the chain as it becomes more worn ironically enough.

Anyway, is it the same for ladies in terms of bodily collisions with handbar stems??!!


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PostPosted: Tue Aug 07, 2012 9:45 pm 
Retro Guru

Joined: Fri Apr 28, 2006 8:42 pm
Posts: 783
Location: Brighton
Check also that you haven't got worn, hooked teeth on the chainring - that can cause the chain to drop when backpedalling.


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