Limited chain rattle - front mech.

[merlin321]

Hi all,
I have a 9 speed triple on an scr2.
The largest and smallest rings have a full range of gear selection with no rubbing or slipping anywhere. On the middle ring being in gears 1-5 is fine, but going into 6 the chain begins to rub on the front mech and 7,8 and 9 are rubbing continuously.
Changing up and down through any gear is smooth and easy so I don`t want to go tinkering and bugger up what I`ve already got, but the rubbing noise is spoiling an otherwise great ride.
Any ideas?

Many thanks.

 

[gwhite]

Sounds like this could be a cable tension problem. With the chain on the middle ring and the largest sprocket, the chain should just miss the inner plate on the cage. If not then adjust the tension to achieve this. I take it that you don't have a "trim" adjustment on your front changer?
Indexed front changers are more trouble than they are worth in my opinion. A Campag type ratchet is much more practical.

 

[mickle]

What gwhite said ^.

But. It's the limit screw which determines the resting position of the cage plate and this should be the starting point for any adjustments. Is the cage plate perfectly parallel to the chainset? Does the cage clear the chain by 2mm in the lowest gear? Is there 2mm of clearance between the top of the big ring and the lower edge of the cage plate when in the middle ring? If the front mech is aligned correctly and the cable has any slack in it when in the smallest ring try undoing the inline cable adjuster a turn or two.