# Front Derailleur Cage Rub In Middle Ring???



## bowler1 (Mar 19, 2005)

My chain is rubbing on my front derailleur cage when in the middle chain ring (I have a triple). It rubs when in the lower two gears in the rear (two biggest cogs). 

This does not quite make sense to me. I can see rubbing when in the small or large chain rings due to chain line issues, but not in the middle.

I am running a dura-ace front derrailleur, 10 speed compatible, and running it with 9 speed cassette and chain.

Could it be that the cage is too narrow being designed to work with the narrower 10 speed chain? Do I just have too much cable tension? Is the derailleur mounted crooked? 

I have tried adjusting the hi/low adjustment range to move the derailleur cage but this did not work. 

How do I correct this?


thanks

Matt


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## TurboTurtle (Feb 4, 2004)

bowler1 said:


> My chain is rubbing on my front derailleur cage when in the middle chain ring (I have a triple). It rubs when in the lower two gears in the rear (two biggest cogs).
> 
> This does not quite make sense to me. I can see rubbing when in the small or large chain rings due to chain line issues, but not in the middle.
> 
> ...


Go to http://www.parktool.com/repair/ and follow the adjustment procedure. The hi/low adjustment screws do NOT move the D. They only provide the extreme inside and outside limits. Do yo realize that there are at least 5 trim positions on the front? - TF


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## cxwrench (Nov 9, 2004)

take to a good mechanic. have him adjust it. ask if he'll show you how to adjust derailleurs. are you also running a 9spd era crankset? what c-ring sizes? the new 7800 fr der is designed to work w/ a 39 middle c-ring, the older crank has a 42. this causes problems.


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## TurboTurtle (Feb 4, 2004)

cxwrench said:


> take to a good mechanic. have him adjust it. ask if he'll show you how to adjust derailleurs. are you also running a 9spd era crankset? what c-ring sizes? the new 7800 fr der is designed to work w/ a 39 middle c-ring, the older crank has a 42. this causes problems.


Yup, didn't pick up on that in the OP. The 10-speed FD will run in to the the 42. - TF


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## bowler1 (Mar 19, 2005)

I'll check on the middle ring. I think it may be a 42. 

My point about the hi/low adjustment was that they do move the extreme to which the derailleur cage will move. When too constrictive it can cause you chain to rub when in the inner or outer ring. 

Just does not make sense to me as to why the chain is rubbing the derailleur cage in the middle ring. I have been mountain biking for years and have not had this problem before on a mountain bike.

I'll check out the tooth number on the middle ring. 

Just trying to avoid a trip to the bike mechanic....closest good bike shop is about 45 minutes and by appointment only, etc. 

Matt


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## Bob Ross (Apr 18, 2006)

iirc Shimano documentation considers the 1st & 2nd (as well as the penultimate & ultimate) cogs to be "crosschained" from the middle ring in a triple. 

I could be totally wrong...but I remember seeing a diagram in the manual for my wife's Ultegra triple and thinking "wtf? Do they seriously mean a dozen gear combinations are unavailable?!?!"


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## TurboTurtle (Feb 4, 2004)

Bob Ross said:


> iirc Shimano documentation considers the 1st & 2nd (as well as the penultimate & ultimate) cogs to be "crosschained" from the middle ring in a triple.
> 
> I could be totally wrong...but I remember seeing a diagram in the manual for my wife's Ultegra triple and thinking "wtf? Do they seriously mean a dozen gear combinations are unavailable?!?!"


No, I have only seen the recommendation to not use the largest and smallest with the middle, the two largest with the large and the two smallest cogs with the small chainring. I normally use the middle with all the gears without rubbing the FD cage (using the two trim positions) on 9-speed Ultegras. - TF


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## Bob Ross (Apr 18, 2006)

TurboTurtle said:


> I have only seen the recommendation to not use the largest and smallest with the middle, the two largest with the large and the two smallest cogs with the small chainring.


That's probably what I was thinking of.


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## Al1943 (Jun 23, 2003)

You do know, of course, that with Shimano road triples there are two shifter positions for the middle ring, one for the left extreme left cassette cogs and one for the extreme right cassette cogs.

Al


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