MTB Front Derailler problem

[Matt Peeler]

I built a Mountain bike over the winter and I used it mostly for dirt road riding and I have a
46/36/26 crank and a Alivio FD using 8sp on the back. The problem I have is this. Everything seems
to be smooth on the 2 lower rings except that it won't shift from the middle to the small ring
correctly. When I shift to the 46 ring, it seems that the chain rubs against the inside of the FD
until I move down to the smaller cogs. And also when I downshift from the big ring it jumps to the
small ring.

Any suggestions? It looks like to me that moving the entire FD up would eliminate the big ring rub
on the inner part but not sure it that might mess everthing else up. I am sort of worn out trying to
make adjustments with the limited screws so not sure which way to go now.

Thanks

Matt P

 

[Dan Daniel]

On 5 Mar 2004 06:05:00 -0800, [email protected] (Matt Peeler) wrote:

>I built a Mountain bike over the winter and I used it mostly for dirt road riding and I have a
>46/36/26 crank and a Alivio FD using 8sp on the back. The problem I have is this. Everything seems
>to be smooth on the 2 lower rings except that it won't shift from the middle to the small ring
>correctly. When I shift to the 46 ring, it seems that the chain rubs against the inside of the FD
>until I move down to the smaller cogs. And also when I downshift from the big ring it jumps to the
>small ring.
>
>Any suggestions? It looks like to me that moving the entire FD up would eliminate the big ring rub
>on the inner part but not sure it that might mess everthing else up. I am sort of worn out trying
>to make adjustments with the limited screws so not sure which way to go now.
>
>Thanks
>
>
>Matt P

What's the spacing between the derailleur cage and the large chainring? I recently moved my Alivio
down so that it barely clears the large chainring and things are fine. This is with a 44 tooth
ring, not a 46.

The limits screws do two things, and two things only. On the inner movement, I set it so that on the
small chainring/large cog, it has *just* stopped giving me rub. On the outer movement, large
chainring/small cog- just where rub stops again.

All other shifting is set by the cable tension. If you are dropping the chain on a downshift, from
large to middle, the cable tension is too loose.

There is a chance that you will get chain rub in some combos no matter what you do- large chainring
and larger cogs is one place that I expect it, and I avoid the largest 2 or 3 cogs most of the time.

My Alivio front derailleur has developed a lot of slop in less than a year. I am surprised by this,
but it is my first top swing derailleur. Maybe the slop is normal, or maybe it has just worn with
minimal use. Try wiggling the cage by hand to check for excessive wear.

Well, maybe others will have better suggestions or more experience. I am doing mainly road riding
and the Alivio has worked just fine. I am putting little stress on it.

The following comments might be of help. Lots of the comments are, well, let's just say misinformed,
but sometimes reading through them I have found either a definite pattern or a tip hidden in there
that has helped me get a component working-

http://www.mtbreview.com/reviews/Derailleur/product_20845.shtml