Ok so I posted a while back about this same issue and I thought it got resolved but it is like it got worse tonight when I tried to make an adjustment and I can't figure out how it EVER seemed like it was working right.
Bike: 54 cm Specialized Sirrus Sport Disc 04 all stock Check the link for the equipment on the bike.
The situation has been that the chain will jump off the inside and do the chain suck thing. As a result my wife (this is her bike) only rides on the middle ring for fear of the chain falling off. So we were going to go on a ride tonight and I figured I could make an adjustment to make he shifting a bit better...well I wound up tearing down the whole drivetrain. Here is what I have done. Check the centering of the BB (it is centered), checked the height of the FD, checked the limits of the FD, check and adjusted and adjusted and adjusted the tension of the FD cable...there is no good tension. Checked the angle of the FD and tried several different angles...I think it is currently optimized.
The only thing I can figure is that the front shifter isn't functioning properly and here is why: The Shimano flatbar front shifter work like the road systems and have a trim in the middle ring, so essentially there are 4 FD positions for the 3 rings. If I set the tension properly on the front in the small ring a push of the shifter does NOT get me to the middle ring I have to push it to the next click...this is also the way it works on my Marin (same Shimano flatbar setup but it is a 9 spd rather than 8) but then you can do a "small" click and get to the inside of the middle ring...this is the trim feature. On the Specialized you have to give it 2 clicks to get on to the middle ring but then if you try to do the small click to goes ring back down to the small ring. Also if the tension is set properly when you are in the small ring (i.e. very little to no rub when in small ring and large cog) when you go to the big ring it will rub like a mother even though it hasn't reaching the outer limit as set by the limit screw. If you then try to shift to the middle ring it gives a micro click (my Marin doesn't do this) but doesn't shift down...another click will send it to the small ring so there is no way to get the middle ring from the large ring. If you add tension to the point that there is little to no rubbing when in the large ring and the small cog you can now get a small click then another down to the middle ring and then another big one down to the small ring but there is constant rubbing when in the small ring as the cable still has tension and the FD isn't at the lower limit.
So all I can say is WTF?!?!?! I am totally baffled. My Marin with nearly the same components works differently and...well it works.
Anyone got a clue here?
Edit: Seems I was not clear: This ISN'T a limit screw issue. This also isn't a cable tension issue, I spent 2 hours on this last night and tried even imagineable amount of cable tension. This also isn't a FD height issue...it is 2mm above the big right as it is supposed to be. This could be a FD angle issue but I don't think it is as I tried it a bunch of different ways from the heel of the FD in to square to the heel of the FD out...nothing works.