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tuning 105 triple front derailleur(3 posts)

tuning 105 triple front derailleurJs Haiku Shop
Feb 25, 2002 12:30 PM
last year's 105, triple. i've replaced the f.der cable and am having serious problems getting it to act right. zinn's book says shift to the inner/small chainring and pull the f.der cable tight with a pair of pliers, then tighten the f.der cable bolt. i do this, then adjust the high/low limit screws, and find that shifting up to larger chainrings is fine, but shifting down from larger to smaller is flakey at best, and often the lever for the downshift does not return to it's starting position (doesn't snap back). it was shifting marginally before replacing the cable, and i noticed at that time that the cable was quite slack with the chain on the inner/small ring.

this is the *first* time i've changed any cables on a bike with STI, so i'm not sure if i'm totally fudging the job, or if it's something else. what am i missing or doing wrong?
...and i just saw SW's post about cable tension...Js Haiku Shop
Feb 25, 2002 12:34 PM
guess i'll need to try this. i'm doing the reverse: attach cable, then set limits. any other suggestions, though?


Posted by: Spoke Wrench
Feb-25-02, 12:26 PM

I have a couple of points regarding the above posts.
1. Completely disconnect your front shift cable before setting the low gear limit screw. If you don't, you may adjust the derailleur against cable tension rather than the limit screw. If you do this, you will lose the chain on the inside as the cable stretches.

Ultegra STI levers actually have four shift points. Shimano suggests that on a two chainring set up you use the three left-most positions and use the high gear limit screw to block off the fourth. Consequently, you have three shift positions for two rings. The third (middle) position allows you to trim the derailleur in either chainring.
STI triples can be a pain.Spoke Wrench
Feb 25, 2002 2:48 PM
If it wasn't working right before, the first thing I would do would be to examine the position of the derailleur on the seat tube. The outer plate of the cage should be parallel with the big chain ring and should just miss the big ring by about 2mm.

When you're sure that's right, shift onto the big cog in back and put the chain on the little ring in front. The inner cage plate, without the cable attached, should just miss the chain by 1 or 2mm.

Now attach the shift cable. Make sure your shifter is in the lowest gear position. I use my needlenose pliers to just pull it snug. I hope your barrel adjuster is in a useable location.

Good luck.