Front mech dropping chain

[Owboduz]

I've had my road bike for three weeks now. The front mech worked well for the first two weeks, but this week, it has begun dropping the chain. I've now dropped my chain six times in the past three days. Each time I adjust the front mech, it seems okay until I ride it a bit, then it starts dropping the chain on the up-shift. It's as though the upper limit is drifting. I've tried setting the limits a little tighter, but then I can't shift into the large chainring. Do I need to tweak the tension? Add some threadlocker? Get the limit set just right?

 

[oldbobcat]

For starters, here's a link to the bible of front derailleur adjustment: http://www.parktool.com/blog/repair-help/front-derailleur-adjustments

Read closely and see if yours conforms.

In my experience, most overshifting problems occur because the outer limit screw is too loose. Once the chain is on the big ring, the cage needs to come to a dead stop. Here are the rest of my tips:

• Make sure the outer plate is absolutely parallel to the rings, and that it clears the tallest teeth on the big ring by no more than 1-2 mm; owners of non-conforming triples may have to set higher to get the inner plate to clear the middle ring.
• Cable tension should be set so the cage kisses the outer limit screw simultaneously with the cable reaching maximum tension. Triple owners should set tension so that the chain goes up to the middle ring from the small ring, consistently from all chain positions on the rear cogs. Double owners should set tension so the outer plate barely clears the chain when it's in the highest (outside-outside) position, and then tighten the limit screw until it just touches.
• The limit screw should allow no movement (or barely perceptible movement) of the cage once it's shifted into the outermost position.

 

[CAMPYBOB]

Quote by Owboduz:
"Add some threadlocker?"

Yes. By all means.

I've seen many spring-loaded derailleur limit screws move. Some screws now come pre-coated with a thread locking adhesive and even those can sometimes benefit from a drop or two of Loctite blue.

Note the slot orientation of your high limit screw when you tune your throw to perfection. Then go out and do a quick test ride (before adding the thread locking adhesive) and just shift the hell out of the front derailleur. Check to see if the screw has moved after a hundred shifts or so.

Follow OBC's instructions for aligning and height-setting your derailleur. Once aligned to the chainrings and the clearance set to minimum, tuning the limits of the throw will be easier.

 

[alfeng]

Originally Posted by Owboduz
I've had my road bike for three weeks now. The front mech worked well for the first two weeks, but this week, it has begun dropping the chain. I've now dropped my chain six times in the past three days. Each time I adjust the front mech, it seems okay until I ride it a bit, then it starts dropping the chain on the up-shift. It's as though the upper limit is drifting. I've tried setting the limits a little tighter, but then I can't shift into the large chainring. Do I need to tweak the tension? Add some threadlocker? Get the limit set just right?

Dropping the chain or throwing the chain?

You have described a front derailleur which is throwing the chain ...

So, the question is WHAT-or-WHICH front derailleur do you have on your bike?

What shifters do you have on your bike?

What chain does your bike have?

Did you buy a NEW bike or was it used-but-new-to-you?

Does your bike have a Double OR Triple crankset?

 

[Owboduz]

I have a FSA compact double chainset with Shimano Claris shifters and derailleurs. The bike was new, period. It was purchased from an online retailer, which leaves me doing my own maintenance or paying to have it done.

After fine tuning the limits, I rode 42km today without throwing the chain. However, when I got back from the ride, as I was putting my bike away, the chain fell off the inside ring, while the chainguide was in the outside ring position, and got lodged between the bottom bracket and the chainset. It was a huge pain to get it out of there.

 

[alfeng]

Originally Posted by Owboduz
I have a FSA compact double chainset with Shimano Claris shifters and derailleurs. The bike was new, period. It was purchased from an online retailer, which leaves me doing my own maintenance or paying to have it done.

After fine tuning the limits, I rode 42km today without throwing the chain. However, when I got back from the ride, as I was putting my bike away, the chain fell off the inside ring, while the chainguide was in the outside ring position, and got lodged between the bottom bracket and the chainset. It was a huge pain to get it out of there.

FWIW. In addition to oldbobcat's & CAMPYBOB's advice, I think that you are possibly going to need to wait for someone else to give you a better (?) answer because MY boilerplate reply is to replace the Shimano shifters with a pair of Campagnolo shifters when an otherwise unresolvable problem with a pair of Shimano shifters is encountered (front and/or rear) -- it's a FAST & EASY conversion (IMO) which is partially offset with re-selling the Shimano shifters on eBay.

 

[Owboduz]

Quote:
Originally Posted by alfeng . I think that you are possibly going to need to wait for someone else to give you a better (?) answer because MY boilerplate reply is to replace the Shimano shifters with a pair of Campagnolo shifters when an otherwise unresolvable problem with a pair of Shimano shifters is encountered ...

I don't think I have encountered an unresolvable issue. I think I have an incorrectly installed front derailleur; a project I hope to tackle this weekend.

Personally, I take all of this as yet one more example of precisely why electronic shifting is necessary. It's just too expensive currently. On the other hand, I've seen the price of good non-electronic groupsets and I believe that there's space for someone to come in and take the bottom out of the shifting market with an electronic system.

 

[oldbobcat]

Originally Posted by Owboduz
After fine tuning the limits, I rode 42km today without throwing the chain. However, when I got back from the ride, as I was putting my bike away, the chain fell off the inside ring, while the chainguide was in the outside ring position, and got lodged between the bottom bracket and the chainset. It was a huge pain to get it out of there.

Aye, that's happened to me too. Anything can happen while storing a bike, especially if you're hanging it on a hook.

One thing I've noticed is if I drop the chain off the small ring, it's while shifting onto the small ring while on a smaller (faster) cog in back. The combination of a sudden slackening of the chain that's already somewhat slack and either the gap between the inner plate of the mech and the chain, or the outer plate hitting the chain with extra force because it's on the outside of its range, seems to throw the chain past its mark.

My advice is (a) don't do this or (b) get a chain-catcher.

 

[Owboduz]

The saga continues. My front derailleur tensioner was so tight that I couldn't move it by hand. I used a pair of plumbing pliers and some cloth to remove the tensioner without marking it. Looking at the threads, it seems like the frame had the wrong thread for the tensioner and the mechanic just forced it in anyway.

 

[oldbobcat]

Originally Posted by Owboduz

The saga continues. My front derailleur tensioner was so tight that I couldn't move it by hand. I used a pair of plumbing pliers and some cloth to remove the tensioner without marking it. Looking at the threads, it seems like the frame had the wrong thread for the tensioner and the mechanic just forced it in anyway.

I presume you're talking about the cable tensioner (we Yanks call them barrel adjusters) on the frame. These things get corroded and cross-threaded a lot.

Sometimes you can chase the threads on the frame side clean with a fresh adjusting barrel that has clean steel threads and a glob of grease on it. Or if the threads are shot, remove the barrel and find a step-down ferrule to stick in there. Then mount an inline adjuster on the cable between the handlebar or shifter and the frame.

I know, real men don't need adjusters on their front derailleur cables. But we're talking to a non-expert home mechanic here who is going to need more than one try to get it right.

 

[Owboduz]

Originally Posted by oldbobcat

I presume you're talking about the cable tensioner (we Yanks call them barrel adjusters) on the frame. These things get corroded and cross-threaded a lot.

Sometimes you can chase the threads on the frame side clean with a fresh adjusting barrel that has clean steel threads and a glob of grease on it. Or if the threads are shot, remove the barrel and find a step-down ferrule to stick in there. Then mount an inline adjuster on the cable between the handlebar or shifter and the frame.

I know, real men don't need adjusters on their front derailleur cables. But we're talking to a non-expert home mechanic here who is going to need more than one try to get it right.

obc,
I think you have the right idea. I've contacted CRC; we'll see what they say. If it's not helpful, I'm going to try and replace the adjusting barrel. I don't have a cable crimper or any cable ends and it seems that I need to cut off the cable end to get it through the routing guides and out of the barrel, so it's not a completely trivial bit of maintenance.

 

[oldbobcat]

Don't screw around too much. Nothing sucks more than trying to thread a frayed or kinked cable through eyelets and housing. Replace the cable if necessary. Good luck.

 

[alfeng]

Originally Posted by Owboduz
obc,
I think you have the right idea. I've contacted CRC; we'll see what they say. If it's not helpful, I'm going to try and replace the adjusting barrel. I don't have a cable crimper or any cable ends and it seems that I need to cut off the cable end to get it through the routing guides and out of the barrel, so it's not a completely trivial bit of maintenance.

FYI. At this point, re-cutting the cable is probably NOT a good idea.

Depending on the condition of your cable's end, you can try "lashing" the end of a brake-or-derailleur cable with CLEAR or MASKING tape ...

Try to re-twine (for want of a better description) the strands as tightly as possible before taping ...

You will want the tape to NOT be square to the cable AND to create a point with it which you can more easily pass through the hole(s) ...

If the end of the cable is frayed to the point where you cannot "lash" it then a replacement cable for the bike may be in your future.

Originally Posted by Owboduz
I don't think I have encountered an unresolvable issue. I think I have an incorrectly installed front derailleur; a project I hope to tackle this weekend.

Personally, I take all of this as yet one more example of precisely why electronic shifting is necessary. It's just too expensive currently. On the other hand, I've seen the price of good non-electronic groupsets and I believe that there's space for someone to come in and take the bottom out of the shifting market with an electronic system.

FWIW. I cannot say that you are expressing wrong thinking ...

But, installing-and/or-adjusting a mechanical derailleur system is not as complex or imprecise as you seem to be implying that it has been for you.

Even Electronic derailleurs need an initial adjustment AND presumably some subsequent maintenance.

BTWI. I cannot repeat it often enough, IMO, that if a person is having ANY trouble with his/her Shimano (or, ¿SRAM?) shifters/derailleurs, then installing Campagnolo shifters is a FAST-and-RELIABLE fix whose cost is (partially) offset by re-selling the "old" shifters on eBay.

IMO, ONLY those who have not used post-1998 Campagnolo shifters (which are not really that different from the 1st generation Ergo shifters) will argue against using Campagnolo shifters ... and, the older Campagnolo shifters will share the same benefit of improved the improved Cogs found on modern Cassettes & subsequently clean(er) shifting.

 

[Owboduz]

Originally Posted by alfeng FYI. At this point, re-cutting the cable is probably NOT a good idea.

The cable has been crimped off with a proper cable end. Since this is a brand new bike--well, three weeks old--I doubt that cutting and re-crimping the cable would be a big problem, except in available length; they trimmed it to 3-5cm past the front derailleur. The problem is that while I have some pretty potent cutters (Channel Lock 909, for example), the only crimpers I have are for electronics/electrical. I would probably need a cable crimping tool for replacing the cable end.

So cutting the cable is not a problem, but crimping it might be.

Never mind. Cables can be replaced. But they shouldn't have to be on a 3-week old bike, nor should barrel adjusters be cross-threaded or mis-threaded. We'll see what the vendor says.

Originally Posted by alfeng FWIW. I cannot say that you are expressing wrong thinking ...

But, installing-and/or-adjusting a mechanical derailleur system is not as complex or imprecise as you seem to be implying that it has been for you.

Even Electronic derailleurs need an initial adjustment AND presumably some subsequent maintenance.

Sure. That's not what I want. The shimano dealer manual offers a very nice step-by-step process for correctly installing a front derailleur. If you can follow it, it works beautifully. Unfortunately, mine was installed wrong and the barrel adjuster was jammed in, despite taking a superhuman grip, or some kind of wrench, to install.

It may be that what I want out of electronic shifting doesn't exist yet. I just want an electronic system that, given the correct installation, doesn't throw the chain. Remember, while electronic cables may stretch, they won't change shifting performance if they do!

Originally Posted by alfeng BTWI. I cannot repeat it often enough, IMO, that if a person is having ANY trouble with his/her Shimano (or, ¿SRAM?) shifters/derailleurs, then installing Campagnolo shifters is a FAST-and-RELIABLE fix whose cost is (partially) offset by re-selling the "old" shifters on eBay.

IMO, ONLY those who have not used post-1998 Campagnolo shifters (which are not really that different from the 1st generation Ergo shifters) will argue against using Campagnolo shifters ... and, the older Campagnolo shifters will share the same benefit of improved the improved Cogs found on modern Cassettes & subsequently clean(er) shifting.

And, once again, a different shifter will not fix an incorrectly installed derailleur and barrel adjuster. We all know you like Campagnolo. I'm not arguing against them. I'm arguing that changing shifters won't change a derailleur from incorrectly installed to correctly installed.

 

[oldbobcat]

If the cable isn't kinked, frayed, or unraveled in a way that prevents it from being reused, then by all means reuse it. But just because it's a new bike don't put yourself through heroics to save a questionable cable. A bad cable will diminish your riding pleasure indefinitely.

By all means pursue QA issues with the vendor. Good luck with that.

And you're right about Campagnolo. Buying new shifters won't fix the incorrectly installed derailleur or the cross-threaded cable tensioner. And it's stupid to be compelled to upgrade shifters on a brand new bike.

If you don't mind my saying, I see this sort of problem at work every week, and we'd most surely get it fixed for $10-25. But pursue it with the vendor first.

Regarding the cable tensioner, have you taken pliers to it, unscrewed it, and looked at the damage yet?

 

[Owboduz]

Originally Posted by oldbobcat If you don't mind my saying, I see this sort of problem at work every week, and we'd most surely get it fixed for $10-25. But pursue it with the vendor first.

Regarding the cable tensioner, have you taken pliers to it, unscrewed it, and looked at the damage yet?

If I can't get any joy via the vendor, I'll either take it to the LBS or DIY it if it looks doable. I'm generally pretty competent, mechanically, just inexperienced and I don't have all the bike-specific tools yet.

I have pulled the barrel adjuster out... I'm not sure what to make of it. I'll try to get a decent macro shot of the threads.

 

[Owboduz]

You should be able to see that there's something wrong with the threads in these. I can upload larger if these aren't big enough.

 

[Owboduz]

This should be better.

 

[oldbobcat]

I'll bet the male thread took most of the damage and the female (frame) thread is pretty intact. If you can't wait for the vendor, get a replacement at local shop and use it to chase the threads with a glob of grease before reassembling it for keeps. Even better, see if he has a steel bolt that matches this.

You shouldn't have to go through this on a new bike.

 

[Owboduz]

Originally Posted by oldbobcat
I'll bet the male thread took most of the damage and the female (frame) thread is pretty intact. If you can't wait for the vendor, get a replacement at local shop and use it to chase the threads with a glob of grease before reassembling it for keeps. Even better, see if he has a steel bolt that matches this.

I will definitely give that a try if I can't get any results through the vendor.

Originally Posted by oldbobcat You shouldn't have to go through this on a new bike.

I agree. And their response to this will certainly decide the tone of the review that I submit to this and other sites. I'm waiting for the ultimate end of this exchange before I finish writing my review of this bike.

I recognize that this is the problem with purchasing a bike from an online vendor. If something goes wrong, you can't go back to the shop. There is a certain element of buyer beware. Hopefully, they will resolve this sensibly.