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Old 10-24-08, 01:30 PM   #1
ehilge
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Front Derailleur... UGH!

Hey all, So I've been having trouble with my front derailleur lately. Last week I think I somehow jammed the chain in between the derailleur and cahinring or something like that and my shifting hasn't been the same since. I've tinkered with it quite a bit but haven't benn able to fix it. Last week I had it working in and out of low gear (I have a compact w/ 105 derailleur) but still overshifting and undershifting in high. Today I was working on it more and now its fine in high gear but won't drop to low. After loosening the limit screw and cable tension to no avail, I inspected the derailleur and realized that it actually is not hitting the limit screw even when the cable is unattached. I don't see any pieces of debris or anything that may be limiting motion. And it can't just be the derailleur b/c it was working fine before my little incident. I also tried tri-flowing it and cleaning up the derailleur a little. Any ideas on what the problem could be, any chance it could have incurred some damage even though I can't see anything obvious?
Thanks for your help!
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Old 10-24-08, 01:44 PM   #2
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How do you know it's not hitting the limit screw?
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Old 10-24-08, 02:39 PM   #3
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Usually there's an extension of the parallelogram arm that contacts the limit-screws. Definitely easy to spot when it touches the tip of the limit-screw. I'd suggest you start from the beginning and re-position the FD correctly on seat-tube before trying to make cable & limit-screw adjustments. Those won't do any good if the FD is too high above the chainrings or if it's rotated incorrectly (parallel to chainring IS incorrect, regardless of what bike-shop monkeys tell you).

http://www.parktool.com/repair/readhowto.asp?id=75




You actually want the tail of the FD to be rotated outwards a little to be parallel with the chain (when set in tallest gear). This gives you a better sweep of the RD before having to trim.

Last edited by DannoXYZ; 10-24-08 at 03:13 PM.
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Old 10-24-08, 03:10 PM   #4
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I just installed a Shimano XTR on my Trek FX 7.5. This gives some perspective on the closeness of the derailleur to the outer chainrings at it's closest during shift.

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Old 10-24-08, 03:14 PM   #5
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Also make sure the FD cage isn't bent.
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Old 10-24-08, 03:23 PM   #6
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A top view would indeed show the outer cage (the one you see closest to you above) is aligned with the chainrings and the chain.

When installing the FD - make sure the outer-cage (on a triple chainring crankset) is adjusted so it does not run into the large chainring when it's shifting from the small (inner) ring and the middle ring. During this shift, it will come closest to the outer (large) chainring as shown in the photo.

Last edited by Panthers007; 10-24-08 at 03:27 PM.
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Old 10-24-08, 03:32 PM   #7
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Front derailler... the best fix would be to get rid of it. Front deraillers are the worst, clunkiest performing part on any bike. I hope that Shimano or someone licenses that Shlumpf 2-speed crankset and that becomes the standard.

Sorry this was totally unhelpful.
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Old 10-24-08, 03:56 PM   #8
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On Shimano's newer front-derailleurs, they put that little depression into the front part of the outer cage-plate. This emulates the effect of having the tail-end of the caged rotated outwards. So on these designs, you want the FD parallel with the chainring. On older designs with simple flat outer-cage, you'll want to rotate the tail outwards so that it's parallel with the chain when shifted into the big-chainring/small-cog combo.
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Old 10-24-08, 06:24 PM   #9
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Originally Posted by drpaauwe View Post
Front derailler... the best fix would be to get rid of it. Front deraillers are the worst, clunkiest performing part on any bike. I hope that Shimano or someone licenses that Shlumpf 2-speed crankset and that becomes the standard.

Sorry this was totally unhelpful.
Double chainring front deraillerus 105+ are perfectly fine and shift fine. The only problem is when you start putting low end components (re: $5 wholesale FD's) and triples together.

Then you have a recipe for annoyance.
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Old 10-24-08, 09:27 PM   #10
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I know its not hitting the limit screw because when I look into the derailleur I can see a small gap between the limit screw and the part of the derailleur that should hit the limit screw, and this is when the cable is unattached. I am a former bike mechanic so I'm familar with how derailleurs work and how they need to be adjusted. Given, I never got very good at front derailler adjustments so theres still a chance its not adjusted correctly. Last week I took the derailleur off and readjusted everything. I also looked to see if the cage was bent but it didn't seem like it to me. Here are a couple of photos of what have right now for what its worth. In the first one you can just see the small gap between the limit screw and the derailleur. And now that I look at it I could probably drop the derailleur a little and se if that helps.
Thanks for you input!
Attached Images
File Type: jpg front derailleur_01 ed.jpg (95.6 KB, 13 views)
File Type: jpg front derailleur_05.jpg (94.4 KB, 16 views)
File Type: jpg front derailleur_08.jpg (90.6 KB, 14 views)
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Old 10-24-08, 09:35 PM   #11
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Yeah, you can drop the FD a lot. It has to do with angles and for the FD to bend the chain 10-degrees, it has to move a lot farther laterally if it's high.

Also if you bend the tip of the inner cage towards the outside a tiny bit, it'll really help it shift from the small ring to the big.
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Old 10-27-08, 06:52 PM   #12
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What I was kinda getting at was whether the cage would go all the way to the limit screw if you pushed it. In other words, was it getting hung up by something else? If it won't hit the screw when unattached, I'd say there's something wrong with it.

As an aside, I'm having a similar problem right now. I tweaked my barrel adjuster to relieve some rattle and the thing wouldn't shift down to the granny (triple) with a slack cable. So I dropped the lower limit 1/2 turn. Later in the ride the thing started overshifting and I had to raise the LL 1.5 turns to get it back to normal ! WTF?? I haven't had to time to spend trying to figure this out, but know that you're not alone. I'm starting to believe that all FDs are cursed.
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Old 10-27-08, 07:49 PM   #13
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Quote:
Originally Posted by operator View Post
Double chainring front deraillerus 105+ are perfectly fine and shift fine. The only problem is when you start putting low end components (re: $5 wholesale FD's) and triples together.

Then you have a recipe for annoyance.
Maybe I've gotten lucky but I've never had problems tuning even the crappiest FD paired with the crappiest crankset on department store bikes, and yes, they were triples. The two Sora triples and the one Acera triple currently in my garage were equally as easy. My Ultegra triple shifts quicker/smoother but that should be expected.
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