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Main
Date: 04 Aug 2007 18:34:40
From:
Subject: Front Derailleur Problems
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First time that I've installed a front derailleur - it's an XTR top
pull with a 46-38-28 triple. I alinged it with the big chainring
using a 2mm clearance. I'm pretty sure I've adjusted the roatation
properly. The problem is that when I am in the big chainring and
eliminate chain rub, I get massive rub on the inner plate with the
middle chainring. I'm well within the stated capacity (22). It's a
slightly bigger ring than the recommended (44), but I'm assuming that
is not the problem. I suppose I can fix the problem by increasing the
derailleur/chainrign clearance so the middle chainring falls under the
inner plate, but I would guess that would affect performance.
Kind of confused - I've adjusted for chain rub hundreds of times, but
never had problems with chainring rub. Am I missing something? Do I
need to bend the plates? Is there some sort of cage diameter capacity
that I've never heard of? I'd appreacite any input.
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Date: 04 Aug 2007 22:57:57
From:
Subject: Re: Front Derailleur Problems
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On Aug 4, 9:26 pm, David Bonnell <dbonn...@gmail.com > wrote:
> > > Kind of confused - I've adjusted for chain rub hundreds of times, but
> > > never had problems with chainring rub. Am I missing something? Do I
> > > need to bend the plates? Is there some sort of cage diameter capacity
> > > that I've never heard of? I'd appreacite any input.
>
> I would raise the clamp before bending or modifying the mechanism,
> just to see if you *can* shift.
> I finally got my 48-36-26 working, but had to compromise a bit...I
> accepted a slow upshift for a reliable downshift.
> This isn't the same issue that you're having, but my point is that a
> bit of trial and error can go a long way.
> Unfortunately, a derailleur modification error can be tough to recover
> from.
>
> How much is your middle ring overlapping the inner plate?
> Why the non-standard ring combination? Did you replace just your big
> ring?
>
> > Raising or modifying (cutting) the derailer is the only thing you can
> > do, other than use a smaller middle and possibly inner ring, or larger
> > big ring. FD's have a "min difference between top and middle ring"
> > spec. It's 12t for most Shimano mtb derailers.
>
> Thanks for pointing that out...I had always assumed the 12t was a
> *maximum*, not a minimum. Although my bike originally had a 10T
> difference (42-32-22)...perhaps I had a 'special' front derailleur.
I've been playing around with the height adjustment - I've stopped the
rub, but now it won't reliably shift into a lower ring. The overlap
on the ring is quite significant - about 4-5 mm. Somehow I think even
throwing a 50 on the big chainring (to make it a 12T front-middle
difference) won't even do it.
The non-standard spacing is just ignorance on my part. I had a
48-38-28 on and replaced the 48 with a 46 - I didn't forsee this
problem - just paying attention to max chainring size and capacity.
The previous gearing presented no problems to an LX FD. Interstingly
enough, the specific model doesn't seem to exist on the Shimano
website, although it is for sale everywhere (FD M960).
Might have to go with the "custom" fit - picked it up for little $$
anyways....
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Date: 04 Aug 2007 22:37:41
From:
Subject: Re: Front Derailleur Problems
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On Aug 4, 10:00 pm, "KnowWhen2HoldemKnowWhen2Foldem"
<knowwhen2holdemknowwhen2fol...@NOcoxSPAM.net > wrote:
> Is the cage for a double or a triple chain ring? Did you adjust the inner
> plate stop?
>
> <nickzajchow...@gmail.com> wrote in message
>
> news:1186277680.368749.64330@i38g2000prf.googlegroups.com...
>
> > First time that I've installed a front derailleur - it's an XTR top
> > pull with a 46-38-28 triple. I alinged it with the big chainring
> > using a 2mm clearance. I'm pretty sure I've adjusted the roatation
> > properly. The problem is that when I am in the big chainring and
> > eliminate chain rub, I get massive rub on the inner plate with the
> > middle chainring. I'm well within the stated capacity (22). It's a
> > slightly bigger ring than the recommended (44), but I'm assuming that
> > is not the problem. I suppose I can fix the problem by increasing the
> > derailleur/chainrign clearance so the middle chainring falls under the
> > inner plate, but I would guess that would affect performance.
>
> > Kind of confused - I've adjusted for chain rub hundreds of times, but
> > never had problems with chainring rub. Am I missing something? Do I
> > need to bend the plates? Is there some sort of cage diameter capacity
> > that I've never heard of? I'd appreacite any input.
Hmmm...didn't think about it being a double cage - I just assumed that
all MTB FDs were for triples. What exactly is an "inner plate stop"?
Do you mean the limit screws? Never heard that term...
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Date: 05 Aug 2007 01:00:18
From: KnowWhen2HoldemKnowWhen2Foldem
Subject: Re: Front Derailleur Problems
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Is the cage for a double or a triple chain ring? Did you adjust the inner
plate stop?
<nickzajchowski@gmail.com > wrote in message
news:1186277680.368749.64330@i38g2000prf.googlegroups.com...
> First time that I've installed a front derailleur - it's an XTR top
> pull with a 46-38-28 triple. I alinged it with the big chainring
> using a 2mm clearance. I'm pretty sure I've adjusted the roatation
> properly. The problem is that when I am in the big chainring and
> eliminate chain rub, I get massive rub on the inner plate with the
> middle chainring. I'm well within the stated capacity (22). It's a
> slightly bigger ring than the recommended (44), but I'm assuming that
> is not the problem. I suppose I can fix the problem by increasing the
> derailleur/chainrign clearance so the middle chainring falls under the
> inner plate, but I would guess that would affect performance.
>
> Kind of confused - I've adjusted for chain rub hundreds of times, but
> never had problems with chainring rub. Am I missing something? Do I
> need to bend the plates? Is there some sort of cage diameter capacity
> that I've never heard of? I'd appreacite any input.
>
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Date: 04 Aug 2007 21:26:45
From: David Bonnell
Subject: Re: Front Derailleur Problems
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> > Kind of confused - I've adjusted for chain rub hundreds of times, but
> > never had problems with chainring rub. Am I missing something? Do I
> > need to bend the plates? Is there some sort of cage diameter capacity
> > that I've never heard of? I'd appreacite any input.
>
I would raise the clamp before bending or modifying the mechanism,
just to see if you *can* shift.
I finally got my 48-36-26 working, but had to compromise a bit...I
accepted a slow upshift for a reliable downshift.
This isn't the same issue that you're having, but my point is that a
bit of trial and error can go a long way.
Unfortunately, a derailleur modification error can be tough to recover
from.
How much is your middle ring overlapping the inner plate?
Why the non-standard ring combination? Did you replace just your big
ring?
> Raising or modifying (cutting) the derailer is the only thing you can
> do, other than use a smaller middle and possibly inner ring, or larger
> big ring. FD's have a "min difference between top and middle ring"
> spec. It's 12t for most Shimano mtb derailers.
Thanks for pointing that out...I had always assumed the 12t was a
*maximum*, not a minimum. Although my bike originally had a 10T
difference (42-32-22)...perhaps I had a 'special' front derailleur.
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Date: 04 Aug 2007 19:19:33
From: Nate Knutson
Subject: Re: Front Derailleur Problems
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On Aug 4, 6:34 pm, nickzajchow...@gmail.com wrote:
> First time that I've installed a front derailleur - it's an XTR top
> pull with a 46-38-28 triple. I alinged it with the big chainring
> using a 2mm clearance. I'm pretty sure I've adjusted the roatation
> properly. The problem is that when I am in the big chainring and
> eliminate chain rub, I get massive rub on the inner plate with the
> middle chainring. I'm well within the stated capacity (22). It's a
> slightly bigger ring than the recommended (44), but I'm assuming that
> is not the problem. I suppose I can fix the problem by increasing the
> derailleur/chainrign clearance so the middle chainring falls under the
> inner plate, but I would guess that would affect performance.
>
> Kind of confused - I've adjusted for chain rub hundreds of times, but
> never had problems with chainring rub. Am I missing something? Do I
> need to bend the plates? Is there some sort of cage diameter capacity
> that I've never heard of? I'd appreacite any input.
Raising or modifying (cutting) the derailer is the only thing you can
do, other than use a smaller middle and possibly inner ring, or larger
big ring. FD's have a "min difference between top and middle ring"
spec. It's 12t for most Shimano mtb derailers.
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