Bicycle Mechanics - Front derailleur problems, at the end of my rope...

I run bar-end shifters. Double crankset. Shifters and cables are roughly 2 yrs old, with 1,000 - 1,500 miles on them.

The problem:
The front derailleur won't shift the chain into the smaller ring up front. Well, it does work OK when the bike is on my workstand, but not when I'm actually on the bike. I followed directions from several sites as to how to adjust the derailleur correctly, and spent quite a bit of time messing about, but I still get the same result. Fiddled with the limit screws, no difference. Tightened the cable manually, no difference. The cable is really slack when I shift into the small ring up front, it just won't pull the chain far enough over. Also, the little barrel adjustor for the front derailleur cable seems to give way whenever I shift... the cable goes slack again.

I assume you've thoroughly cleaned and lubed the FD. If so, shifting into the small ring when you are pushing hard to climb a hill is shifting too late. Shift to the small chain ring when you are not pedaling hard (i.e., when you're at the bottom of the hill before you start your climb). Unless the return spring or pivots on the FD are broken or gummed up, the problem is your technique. The reason is works on the workstand is that the chain is lightly loaded when you're moving the pedal by hand. Hill climbing is a thinking man's game. You have to anticipate the need for the gear and get to it before the chain is too tight. Once it is, the derailleur spring force is not sufficient to pop it off the chain ring.

Lot's of things work perfectly in the workstand, but get them on the road they don't.

For your setup, would first suggest new inner & outers cables.

Then with the FD un set, make sure it is correctly set up for the chain line, and as close to the rings a possible adn the adjustor screws are un-adjusted.

Then follow the instructions as on the link below (take it yours is a Shimano set up), there are also many good tutorials avaliable on youtube.

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/105/FD_5600/SI_5JM0C_001_EN_v1_m56577569830621301.PDF

If all that fails, go to your nearest LBS, and get them to adjust it.

Check the cable guide under the bb shell, too.

Check the cable guide under the bb shell, too.
Do you mean for alignment or for dirt, sand, or rust?

I assume you've thoroughly cleaned and lubed the FD. If so, shifting into the small ring when you are pushing hard to climb a hill is shifting too late. Shift to the small chain ring when you are not pedaling hard (i.e., when you're at the bottom of the hill before you start your climb). Unless the return spring or pivots on the FD are broken or gummed up, the problem is your technique. The reason is works on the workstand is that the chain is lightly loaded when you're moving the pedal by hand. Hill climbing is a thinking man's game. You have to anticipate the need for the gear and get to it before the chain is too tight. Once it is, the derailleur spring force is not sufficient to pop it off the chain ring.

I probably do need to clean and lube it better (though I did a cursory cleaning). It wasn't a problem on hills vs. flats, I was just testing it out riding around my block, which is flat. But still, your point is well take that there is less force on the chain when I'm pushing it by hand...

Do you mean for alignment or for dirt, sand, or rust?
Yes, for grime, wear or something else catching on the cable.

Since you state that shifting down results in noticeable slack in the cable along the downtube, I'd guess that it's either (1)an issue with the bottom bracket cable guide, (2)incorrectly set low limit, (3)poor FD positioning/alignment or (4)corroded or damaged FD spring.

Well, I did everything you guys recommended (thanks btw) save for replacing cable and housing. I think I'll visit my LBS and have them take a gander... they know my amateur mechanic status and will walk me through their adjustments.

The cable acts very funny. I tighten it, an then just slackens up to the utmost extreme once I shift once or twice... further ideas? (just for diagnostics sake)

But still, your point is well take that there is less force on the chain when I'm pushing it by hand...

I speak from experience... My technique is kinda ****ty too. :P

I had a situation with a brake that was somewhat similar, I would tighten the cable down hit the brakes, and the cable would go slack. The plastic housing on the cable had seperated from the metal inside and was compressing and sliding around every time I would squeeze, causing it to shorten slightly every time.

Did it ever work right?

Front derailleurs are real sensitive to their position on the seat tube both up/down and the angle relative to the plane of the chainrings. That doesn't change itself but, if it has never been right, that could be your problem.

If not mech, technique?
Easier to make the big drop to the granny gear by shifting early in the climb, rather than late.

As a old tourist .. a hint.. double shift granny on crank, + to a middle gear in the wheel cluster, bottom of the climb,
that should be a ratio close to your middle chainring / low hub cog gear,
then you have the rear derailleur to make the needed downshifts after that.

let up on pedal pressure before derailing chain.

If the cable is coming loose it sounds like it may be slipping through the clamping screw unless it's that rather odd housing issue. One way to check that is to see if the free end is shorter after the cable goes slack. If so you need to look at some options to let the clamping screw get a better bite on the cable.

Another possible but not likely option given your slackening cable issue is that the bar end shifter has a limited amount of travel intended for use on double ring setups and just doesn't pull enough cable for a triple. But that's unlikely. And in view of the slackening cable issue probably not the cause. If it were you'd find that even with the limit screws at the derailleur totally loose that you would not have enough travel to reach all three rings.

By the way, at least half of being a good mechanic is looking at a system and being able to mentally break it down into sub assemblies for function and test each to see if it's working properley. We are doing this for you sight unseen in the posts we've made and the ideas we've given just based on our knowledge of the parts and how they SHOULD work. You can get to this point but just sitting down at the bike and looking at each part and how they interact and actually think about what is required to do each function. For example you can determine if the deraileur travels far enough to span all three rings by pulling on the cable to pull the derailleur farther than the shifter will pull it. At the same time it's possible that it'll give you some sign of why the cable is going slack on you. It'll also show you if the derailleur is spanning enough travel to reach all three rings. And it would be an indication about the shifter being able to pull enough cable or not.

Also since these are bar end shifters you may want to draw out the cable and check it. If there's broken strands the cable will stretch quite a bit before it finally breaks. You may be dealing with the strands letting go a couple at a time and that is why you're getting slack.

Just to get on the same page. I'm assuming the FD is sprung to shift in on the spring, and out with the cable. If it's the reverse, stop here and disregard the post.

Also because it works on the stand but not on the road, I remind you that the FD works on the tense loop of the chain and therefore cannot lift the chain over the teeth of the outer cog if you don't ease up pedal pressure to reduce chain tension enough. Try totally backing off pedal force during the shift and verify that it's mechanical and not you.

Since the FD moves inboard on spring power not cable and the cable is slack at the down tube, and not binding at the BB shell something other than the cable is the problem. Verify this, by removing the cable entirely and shifting by pressing on the FD's lever arm to shift and observing if it moves back in quickly and positively. Also check that it goes fully to the inner limit, by varying the limit position and checking that it causes changes in the cages innermost position. If not something else is binding the pantograph or limiting it's innermost position.

If you have any doubt at all move the chain out of the way, and work the FD back and forth against the spring. It should snap back very sharply with zero hesitation, and bang hard on the limit. Flush with solvent and oil with light oil until it does.

Now if you've confirmed that the FD itself is OK, start fresh checking height, alignment and cable settings, you should be able to get it right.

If you have any doubt at all move the chain out of the way, and work the FD back and forth against the spring. It should snap back very sharply with zero hesitation, and bang hard on the limit. Flush with solvent and oil with light oil until it does.


Ha ha! I found the problem. Just a frayed cable, didn't see the loose strand the first five times I looked at it, I guess. The FD needed a cleaning, snaps back much better now. Also the cable guide under the BB had a little snag in the plastic i shaved off. Things come in threes, huh? Looks like I'll be good to go once new cable goes on tomorrow... fingers crossed.

Thanks!