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need help Dura Ace front derrailleur(3 posts)

need help Dura Ace front derrailleurbrakemeister
Jun 4, 2002 9:17 PM
I give up.
Neigbhor brought in his Klein Roadbike with Dura Ace derrailleurs and CN 7700 Chain.
The bike is less than 300 miles ...

He has Dura Ace chainrings 53 39 and the dang front derrilleur either rubs on the inside bottom when on the last three large sprockets

or

it barely get the chain up to the large chainring than it rubs there on the last three small sprockets.

I am almost at my end with that "thing" ... the front derrailleur is as paralell to the chain as possible and its only 2 mm above the teeth in the large chainring...

besides the chain rubs on the outer Larger ring when its running on the small ring and you have the small sprocket engaged ( sure not the wisest choice, but should it rub ??)

I need serious help with this one...

Thanks Thorsten
Chainline problem? Derailleur not bent? If okay, then it'sPaul
Jun 6, 2002 4:30 AM
alighment. How are you checking the the chain being parallel to the outer cage? You can also do this by pushing down (if cable attached) on the der. so that it's over the chain, and looking down you can check to see if it's parallel over the chain.

If it's barely getting up to the big ring, the cable is too tight. This won't fix the chain rub, but it's one of your problems.
Another quick check, is to put the chain on the big ring, shift to the 5th cog, and the chain should be dead nuts between the cages(chain line alignment).

Start from scratch.
small chain ring, largest cog
Take off the cable.
Put the barrel adjust so that it has equal adjust thru the housing so that you can trim later.
With cable off, is the der. about 2 mm from the inside plate? Adjust with inner stop.
Pull cable tight(use pliers) and straight thru the groove on the der, and tighten. Cable should be sraight up, not bent over the bolt when properly set.
Shift to large chain ring, small cog, adjust outer stop so that chain is 2 mm from outer plate. If you still have a problem shifting to outer chain ring at this point, you have other problems like the cable is binding in the shifter, not properly inserted. check this once you take off cable.

If done correctly, there should be no chain rub.

Now, if i do get chain rub, I use the barrel to trim. CCW will bring the inner plate closer to the chain, CW away from the chain. This is a little tricky, and I have my own method. Don't remember Shimano instructions exactly.

You really have to make sure chain is parallel to der., if not you can adjust forever and get chain rub.

Front der. in my book is more difficult to set up then the rear. If you can't do it, find a good wrench. Average wrench will usually screw this up. Learn how to do it.
re: need help Dura Ace front derrailleurTheKid
Jun 7, 2002 6:02 AM
I have the same problem. It seems to be the limitation of the shifter that is causing my problem. I adjusted the derailleur by loosening the cable, and made sure the shifter was "reset" to the small chainring. If you adjust the drailleur so the chain does not rub when on the small chainring and largest rear spocket, you can shift onto the large chainring but not far enough to eliminate the chain from rubbing when it is on the three smallest rear sprockets. The shifter seems to have reached its limit and will not allow you to move the derailleur farther out to eliminate the rubbing.