Amateur mechanic needs help with front derailer, can't get to work right.

[kyperman]

I took my rear tire off my new (used) Trek 760 to change the tire. Now I can't get the front derailer to work right. It moves when I shift to the large crank position, but won't move back. In addition, if I am not careful, it moves too far to the large crank position and the chain comes off.

I called my local Trek dealer and they will tune the bike up for 70 dollars, but I don't really want to pay that much if I can do it myself. What am I missing, I have tried to adjust the shift position and loosen things here and tighten them there, but I think I am just making the whole thing worse. Is there any articles or quides out there I can read and follow?

 

[xxamr_corpxx]

Do a gooogle search for Sheldon Brown, or park tool. They have good tips.

 

[RussB]

Park tools website is great, just go to the derailer section and follow the setup in order. Start right after the cable replacement section and check out the setup from there. I've used it to get both on my derailers set up perfectly (30 speed)


http://www.parktool.com/repair/

 

[j.r.hawkins]

For information about bike setup and repair, either of Lennard Zinn's books are great. I have a MTB, so the one I got was "Zinn and the Art of Mountain Bike Maintenance."

I had this problem early on, and ended up replacing the front derailleur with something a little better. The danged thing just didn't cope with the load of my route's steeper hills, badly timed beginner changes, and 80kg weight. It would end up twisting and it ony took a fraction of a millimeter movement for the change to go off. So I got a DR with a stronger band clamp and better cage and pivots.

It turned out the real issue (unreliable changes, chain jumping off and missing the little chainring altogether and wrapping around the BB) was caused by the chain being two link pairs too long, and the rear DR therefore not applying enough tension.

If not for a snippet on chain length I picked up from the Zinn book, I'd still be chasing my tail I reckon, because it slipped right past the LBS mechanics.