The front derailleur on my Trek 1000 has given me problems since I got it. I bought it used, so not sure what the guy who had it before me did with it. I think he may have had different chainrings possibly.
When shifting to the big ring, the chain would often have problems catching, and getting on to it. Other times, the chain would go too far, and fall off the big ring. I played with the limiting screw, but where the heck to set it? In or out?
Yesterday I thought about it, and wondered if the derailluer was set too high above the big ring? When I got home last night, I loaded the bike onto the repair stand, and took a look The cage on the front derailluer was about about 5mm off of the big chainring at it’s closest. My book suggests about 1-3 mm. So I loosened the clamp holding the derailler to the seat post tube, and slid it down a little bit. I tried to adjust the angle of the cage as well. The outside part should be in line with the big ring. But the problem is the sides of the derailluer cage are curved. I wondered if these are supposed to be curved, or are bent. But it looks like it is made that way. So I adjusted the front and back edges of the cage to be lined up with the chain ring. At the suggestion of one website I found, I turned the front edge in about 1% or as close as I could figure. I tightned down the clamp.
I tested the shifting by hand turning the cranks, and shifting the gears into the various gear combinations. The bike now shifted on to the big chainring with no problems. And I didn’t get it to throw the chain off either.
The real rest will be how it handles out on the road. I may need to tweak the limiting screws a little now that I have re-positioned the front derailleur.