|Dura Ace Front derailleur adjustment question||Chas|
Aug 6, 2001 7:24 AM
|The limit screw on my front derailleur seems to vibrate out of adjustment. It must be happening when I'm on the big ring because it actually tightens and prevents a shift to the small ring. I'm planning on using lock tight to solve the problem but was wondering if anyone else has experienced this?|
|Highly Unlikely, but Possible||grzy mnky|
Aug 6, 2001 4:31 PM
|Well it is possible although I've never experienced or heard of this - so what. I had brand new der. this spring that had a stripped hole which resulted in the limit screw always coming loose. If you're going to use Loctite make sure it's the medium strength "blue" type - red is permanent. More likely is that there is something else at work here. Something is loose, the cable housing is too short and is moving, the der. clamp is loose, the pivots are so worn or just loose as to introduce play in the mechanism (very common) and poor shifting, the screw that holds the two sides of the cage together has come loose (very sneaky). If the screw were loose enough to tighten on it's own it would also be loose enough to loosen on it's own when the der. is in the small ring and there is pressure on it. there are only a couple screws other than the limit screws - verify that each one is snug WHILE THERE IS NO LOAD ON THE SYSTEM - that way you feel if something is loose. |
Really what you need to do is keep playing with it and figure out under what conditions does it misbehave such that you can repeat the problem at will. Most of the time mysterious and complex results have surprsingly simple explanations. Good luck - I hope this helps
|Highly Unlikely, but Possible||Chas|
Aug 7, 2001 10:39 AM
|Thanks, I did use the blue, I let it dry overnight so I'll test it later today. |
It is a loose limit screw, I was able to move it by hand when there is no presure on it. I may have caused the problem because when I built the bike I stripped the head of the original limit screw and replaced it with what appeared to be the same size screw. May have been just different enough to cause the problem. Trying to order replacement screws from Shimano. Hoping loctite will work for now.
Thanks for your info.
Aug 7, 2001 3:11 PM
|Replacing the screw with something that wasn't an exact match would explain a lot - maybe everthing. You should be looking in the METRIC section at the hardware store and I'd advise you stick with stainless steel - you want to be able to not worry about it corroding in place, but the SS/Alu. combo isn't good either... |
The best place to get the screw would be out of a trashed unit at a bike shop - the 105 and Ultegra pivots wear easily so there should be a good "bone pile". Here's another tip - if you remove both limit screws you can actually slide out the threaded steel plate that rests inside the alu. der. casting. If you take this with you may have a better chance of getting a good match. You may have changed the size/pitch of the threaded hole with the replacement bolt.
Methinks that a visit to your LBS would be quickest and easiest.