# Chain slips off lower pulley



## TiCoyote (Jun 28, 2005)

I've had this problem sporadically for a few months. When I shift from the large ring to the small ring on a hill, the chain slips off the lower pulley/jockey wheel. I haven't crashed or done anything to damage the RD or the derailleur hangar. Any suggestions?

I'm running Shimano Ultegra 6800.


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## Marc (Jan 23, 2005)

Are your pulley bolts snug?


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## TiCoyote (Jun 28, 2005)

They are. 

Other info: the chain is due for replacement, but I don't think that would cause this sort of problem. Also, this only seems to happen when I shift into the small ring while climbing hard. It generally only does it if I'm in the largest 2 or 3 sprockets.


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## velodog (Sep 26, 2007)

Have you checked the hanger alignment or just trusting it because of no incidents? Any stiff links in the chain?

What kinda shape are the pulleys in, and are the upper and lower pulleys in their proper positions? As in, you haven't had them out and replaced them in reverse order.


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## TiCoyote (Jun 28, 2005)

I haven't checked the hanger. I suppose it could be that. It could also be that the chain line is off. I'm using a Wheels MFG Outboard BB, and I didn't put in any of the spacers. It didn't seem to need them.


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## velodog (Sep 26, 2007)

TiCoyote said:


> I haven't checked the hanger. I suppose it could be that. It could also be that the chain line is off. I'm using a Wheels MFG Outboard BB, and I didn't put in any of the spacers. It didn't seem to need them.


It could be the shims, but not having them would bring the chainrings inboard but the pic looks as if the chain is unshipping outboard. It seems that it would be vici-verci, unless the crankset is floating out to where it would be with the shims in place, but I'm just supposing on both accounts.


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## ericm979 (Jun 26, 2005)

Is the cage spring tension still good? If it's weak the cage won't snap back fast enough when the chain loosens suddenly as it drops to the small ring. So the chain would come off the pulley wheel.

I once had that spring come unhooked inside the derailleur during a ride. It was on the Death Ride and I was a 1/4 mile coast from an aid station with mechanics who had nothing to do. One of them got the spring back into position and had me on my way in about 5 minutes. I never figured out what caused it and it never happened again.


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## TiCoyote (Jun 28, 2005)

The RD is only a year old. I don't think the spring has come off. Maybe this is just a problem with the 6800 drive train. Sometimes, I also get sloppy shifts in and out of the middle cog. I understand this can also be a common problem. 

I see a lot of threads with the suggestion "check the RD hanger." I'm under the impression that this is kind of a difficult job, and it requires an expensive tool.  Is this something that I can really do myself, or is it an LBS job?


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## Peter P. (Dec 30, 2006)

I'm with velodog-have you removed the pulleys and reinstalled them in the opposite positions, or reversed the rotation of the pulleys? Some pulleys have a "direction of rotation" arrow.

A home brew method to ballpark check your derailleur hanger alignment is to put the derailleur in a gear which directly lines up with either chainring. Then sight down vertically from the cogs to the pulleys. The pulleys should line up vertically with each other and the cage should not appear to point to the left or right.

Aligning a hanger with a tool is pretty easy, but if you have an carbon integrated hanger, you can't do it. If you have a bolt-on aluminum hangar, first try tightening the mounting bolts. If that doesn't solve the problem, these hangers are not meant to be aligned; just replace it. And always buy a spare to keep on hand.


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## cxwrench (Nov 9, 2004)

Peter P. said:


> I'm with velodog-have you removed the pulleys and reinstalled them in the opposite positions, or reversed the rotation of the pulleys? Some pulleys have a "direction of rotation" arrow.
> 
> A home brew method to ballpark check your derailleur hanger alignment is to put the derailleur in a gear which directly lines up with either chainring. Then sight down vertically from the cogs to the pulleys. The pulleys should line up vertically with each other and the cage should not appear to point to the left or right.
> 
> Aligning a hanger with a tool is pretty easy, but if you have an carbon integrated hanger, you can't do it. *If you have a bolt-on aluminum hangar, first try tightening the mounting bolts. If that doesn't solve the problem, these hangers are not meant to be aligned; just replace it. And always buy a spare to keep on hand.*


If they're not meant to be aligned how do you know they're straight? 

You can align ANY hanger and if you (or your mechanic) install a new hanger and don't at least check it _you're doing it wrong._ 9 out of 10 hangers on new bikes or new hangers bolted onto a bike are off and need aligning. Doesn't matter if the hanger is perfect, the frame likely isn't. 

As for the OP's problem I'd check the hanger, then see if the cage is bent at all, then check that the pulleys are installed correctly and spin freely.


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## TiCoyote (Jun 28, 2005)

I've never taken apart the cage, so I can't imagine that it's a problem with the pulleys. 

The bike is a Tarmac SL3. It has an aluminum hanger on a carbon frame.


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## cxwrench (Nov 9, 2004)

TiCoyote said:


> I've never taken apart the cage, so I can't imagine that it's a problem with the pulleys.
> 
> The bike is a Tarmac SL3. It has an aluminum hanger on a carbon frame.


Check the hanger alingment or have someone that is a good mechanic check it. A dollar says it's out.


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## velodog (Sep 26, 2007)

TiCoyote said:


> The RD is only a year old. I don't think the spring has come off. Maybe this is just a problem with the 6800 drive train. Sometimes, I also get sloppy shifts in and out of the middle cog. I understand this can also be a common problem.
> 
> I see a lot of threads with the suggestion "check the RD hanger." I'm under the impression that this is kind of a difficult job, and it requires an expensive tool. Is this something that I can really do myself, or is it an LBS job?


If you do your own mechanical work it's a tool worth having. I picked one up a few years ago and it's earned it's place on the bench. The Park DAG 2 can be had for about $70, others are cheaper or more expensive, or there are DIY applications if you'd rather.

Here's the Park tool with a short video on it's use.

Derailleur Hanger Alignment Gauge | Park Tool


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## duriel (Oct 10, 2013)

Take a real close look at all the teeth on the pulley from the rear. I had some that the teeth somehow got out of alignment (or bent) sideways. One could bend them back straight in line with the rest, but it wouldn't last. Had to replace. 

It sounds weird, but I think the plastic aged and tension or something internally would bend them back out of alignment.


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## TiCoyote (Jun 28, 2005)

Is cracking the frame with the derailleur alignment tool a significant risk? Is this a job "best left to the pros"?


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## Lombard (May 8, 2014)

Here's something nobody has brought up. Did the cage that surrounds the pulley somehow get stretched open a bit? Two words: channel locks.


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## bikerjulio (Jan 19, 2010)

The check is done with the RD removed, and the wheel clamped firmly in place. Thus the top of the hanger is clamped also and the hanger takes all the strain.

Many OEM hangers are cheaply made and not really safe to straighten. If you have one of these, just do the check but don't try to "fix" it. Just buy a replacement from Wheels and work with that.


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## velodog (Sep 26, 2007)

TiCoyote said:


> Is cracking the frame with the derailleur alignment tool a significant risk? Is this a job "best left to the pros"?


My bikes are all steel, so no on mine, but if you're concerned most any decent shop should be able to do it for you.

It's my understanding that an aluminum hanger is meant to bend before the carbon fiber frame breaks, but I have no experience other than with my steel.


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## Lombard (May 8, 2014)

If it bends, it's funny. If it breaks, it's not!

https://www.youtube.com/watch?v=D-_Akm40RJQ




bikerjulio said:


> View attachment 313569


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## MMsRepBike (Apr 1, 2014)

TiCoyote said:


> Is cracking the frame with the derailleur alignment tool a significant risk? Is this a job "best left to the pros"?


The biggest concern is probably scratching a brake track on a carbon rim, cracking a frame? No. I think the tool is worth buying and using. Takes a bit of getting used to in order to perform the job correctly but it's not hard.

And as noted above, most all hangers from China are powdered metal and should not be messed with. I refuse to run such hangers on any bike I own, I always put a wheels manufacturing one on as soon as it gets built up the first time. So if you don't already have a wheels one or other cnc cut solid aluminum one, I'd put one on now just because.


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## velodog (Sep 26, 2007)

Lombard said:


> If it bends, it's funny. If it breaks, it's not!
> 
> https://www.youtube.com/watch?v=D-_Akm40RJQ


Safety's no joke,

until someone gets hurt, then it's hilarious.


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## crit_boy (Aug 6, 2013)

I have had a jockey pulley crap out on my 11 speed ultegra derailleur. I have no explanation on the cause or desire to argue with anyone that it didn't crap out. 

The upper got me starting from a stop light. I tried to accelerate and the chain just started jumping. Had to pull off the road. In the roadside diagnosis, the upper pulley was very hard to turn. Luckily, I was close to home. I removed the pulley from the derailleur, cleaned it and re-installed it. A week or so later, it did the same thing while riding on the trainer. Replaced. 

While I haven't seen jockey pulleys crap out all that often, I would maybe figure out whether it is hard to turn by hand. Could be debris (e.g. dog hair) making the pulley difficult to turn or the pulley may just need replaced.


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## ericm979 (Jun 26, 2005)

TiCoyote said:


> Is cracking the frame with the derailleur alignment tool a significant risk?


No. The hanger bends pretty easily.

The cage spring can be weak without being unhooked. At least check that the tension is normal. It's not like it's hard to do.

What you describe is not normal for any drivetrain.


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## bikerjulio (Jan 19, 2010)

I'll second what eric says.

Although we have focussed on alignment, which is certainly worth checking, even with some poorly aligned hangers on my bikes, I've never had anything like that happen.

Easy to check RD tension. Also easy to check that the jockey wheels are moving freely. Take the chain off the small ring to take all the tension off. Pull it away from the jockey wheels and see if they spin. 

If a jockey is sticky it delays the chain being taken up as you shift rings, and it would just flop around for a second, and could well do what you show in the first post.


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## Peter P. (Dec 30, 2006)

cxwrench said:


> If they're not meant to be aligned how do you know they're straight?
> 
> You can align ANY hanger and if you (or your mechanic) install a new hanger and don't at least check it _you're doing it wrong._ 9 out of 10 hangers on new bikes or new hangers bolted onto a bike are off and need aligning. Doesn't matter if the hanger is perfect, the frame likely isn't.


They're not meant to be aligned because they're aluminum, which weakens very quickly if it's manipulated.

If you find an aluminum hanger misaligned, my recommendation is to align it but order a replacement right away. In fact, order two.

It never hurts to check a hanger regardless of whether you can align it. If replacing the hanger does not improve the alignment AND the shifting AND it's because the frame is out of whack, then depending on the frame material you may have bigger problems.

I've read the tolerance for alignment on derailleur hangers is +/- 4mm.


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## cxwrench (Nov 9, 2004)

Peter P. said:


> They're not meant to be aligned because they're aluminum, which weakens very quickly if it's manipulated.
> 
> If you find an aluminum hanger misaligned, my recommendation is to align it but order a replacement right away. In fact, order two.
> 
> ...


I'm pretty sure I've checked and/or aligned hundreds and hundreds more hangers than most...and you HAVE to align them. All of them. Pretty much every new bike needs it done. If I replaced all those hangers the new ones would be out of alignment too.


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## TiCoyote (Jun 28, 2005)

All of the springs in the RD seem to have appropriate tension. Everything moves freely. Jockey wheels spin. 

If my RD hanger is out of alignment, do I:
a: straighten it
b: replace it
c: replace it and straighten the replacement
???


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## Jay Strongbow (May 8, 2010)

Make sure your wheel is in straight. It probably is, but doing so isn't 100% dummy proof like you might think. Just a few days ago I switched rear wheels and gave the cranks a few turns before hoping on the bike and exactly what's in your picture happened. It was because I clamped down the skewer with one side not fully in the drop out.


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## velodog (Sep 26, 2007)

TiCoyote said:


> All of the springs in the RD seem to have appropriate tension. Everything moves freely. Jockey wheels spin.
> 
> If my RD hanger is out of alignment, do I:
> a: straighten it
> ...


I'd straighten the one on the bike and buy a replacement or two to have if needed in the future. Even if I was going to replace the bent one for fear of it breaking, I'd straighten it so it would be right while I waited for the replacement(s) to arrive.

They can't be so expensive that having spares on hand would hurt the pocketbook.


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## bikerjulio (Jan 19, 2010)

velodog said:


> I'd straighten the one on the bike and buy a replacement or two to have if needed in the future. Even if I was going to replace the bent one for fear of it breaking, I'd straighten it so it would be right while I waited for the replacement(s) to arrive.
> 
> They can't be so expensive that having spares on hand would hurt the pocketbook.


If OP is a risk taker who loves to live life on the edge while at the same time having excellent medical coverage, then this advice is fine.

Or why not do things logically, and just check the hanger without doing anything to it.

If bad, then order and install a new one, and align that.

The picture I posted was of a OEM hanger on a Fuji that spontaneously failed on a ride sending the RD into the back wheel.


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## duriel (Oct 10, 2013)

I think the chain is too long. Who put it on and was it ever adj correctly. When your chain drops, if it is long it will be quite slack for a split second.

It would seem that the RD would have to be way out for it not to pick up the chain from the chainrings.


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## bikerjulio (Jan 19, 2010)

duriel said:


> I think the chain is too long. Who put it on and was it ever adj correctly. When your chain drops, if it is long it will be quite slack for a split second.
> 
> It would seem that the RD would have to be way out for it not to pick up the chain from the chainrings.


Possible.

If OP could take a picture from the side of the RD when in the small-small combo then we can advise.


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## Peter P. (Dec 30, 2006)

TiCoyote said:


> If my RD hanger is out of alignment, do I:
> a: straighten it
> b: replace it
> c: replace it and straighten the replacement
> ???


a, then b.

Check the alignment on the original, before straightening. Make note of how far off it is at 12, 9, and 6 o'clock (Three points make a plane-remember your geometry?) so you don't have to check at 3 o'clock, (which is the rim section behind the seat tube.) Manipulating the tool to check the 3 o'clock section is a pain and not necessary.

Straighten it and ride, while waiting for your replacements to arrive.

Install the replacement and check the alignment. If it's off similar to the original, then bring it to a bike shop and explain that the DROPOUT is out of alignment and not the hanger, and you'd like them to correct it.

Of course, if the dropout is made of something other than steel, you can't tweek it.


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## Migen21 (Oct 28, 2014)

I have no idea what is wrong with the OPs bike, but I'd guess more than one of the things already listed.

Re: investing in an alignment tool, i think it is probably the second best bike tool purchase I've ever made ( bike stand is #1).

Since making that investment and leaning how to use it properly, my bikes all shift better. It's saved me countless time and frustration. I just automatically check and adjust the alignment every time i have a chain off. Takes two minutes max.

Sent from my LG-D851 using Tapatalk


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## Jay Strongbow (May 8, 2010)

MMsRepBike said:


> And as noted above, most all hangers from China are powdered metal and should not be messed with. I refuse to run such hangers on any bike I own, I always put a wheels manufacturing one on as soon as it gets built up the first time. So if you don't already have a wheels one or other cnc cut solid aluminum one, I'd put one on now just because.


Took me way to long to learn but I'll second this. Buy two or three while you're at it. Even the "good" ones bend/brake fairly easy, which is an intentional part of how they are made so they break or bend instead of ripping out of the frame and trashing it. Some of the stock ones are complete garbage and don't even hold up to a lot of shifting.


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## bikerjulio (Jan 19, 2010)

Peter P. said:


> a, then b.
> 
> Check the alignment on the original, before straightening. Make note of how far off it is at 12, 9, and 6 o'clock (Three points make a plane-remember your geometry?) so you don't have to check at 3 o'clock, which is the rim section behind the seat tube.) Manipulating the tool to check the 3 o'clock section is a pain and not necessary.
> 
> ...


OP has a carbon framed Scott, so I don't think much realignment of the dropout is going to happen. Plus I will guarantee that it did not come with a steel hanger.


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## bikerjulio (Jan 19, 2010)

I too was dubious that this was just an alignment problem, but then I read the 3 threads linked to at the bottom, all with a similar problem, and all fixed by correcting alignment. 

So I have to think that it's back to either the hanger, or the RD twisted in some way.


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## Blue CheeseHead (Jul 14, 2008)

bikerjulio said:


> If OP is a risk taker who loves to live life on the edge while at the same time having excellent medical coverage, then this advice is fine.
> 
> Or why not do things logically, and just check the hanger without doing anything to it.
> 
> ...


Have you not read CX's posts that straightening a derailleur hanger is normal operating procedure and needs to be done on new bikes AND on new replacement hangers?

Tweaking a piece of aluminum a few times over it's lifetime is not going make it fatigue to the point of failure. Large movements are not involved here.


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## Peter P. (Dec 30, 2006)

Blue CheeseHead said:


> Have you not read CX's posts that straightening a derailleur hanger is normal operating procedure and needs to be done on new bikes AND on new replacement hangers?
> 
> Tweaking a piece of aluminum a few times over it's lifetime is not going make it fatigue to the point of failure. Large movements are not involved here.


If the manufacturers can't build frames that are in alignment, then there's a manufacturing problem.

Perhaps what we're seeing is the difficulty in building carbon fiber frames with straight dropouts. There's no reason the replaceable hanger shouldn't be straight; it's a machined piece of aluminum.


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## bikerjulio (Jan 19, 2010)

Blue CheeseHead said:


> Have you not read CX's posts that straightening a derailleur hanger is normal operating procedure and needs to be done on new bikes AND on new replacement hangers?
> 
> Tweaking a piece of aluminum a few times over it's lifetime is not going make it fatigue to the point of failure. Large movements are not involved here.


You will no doubt be aware that there are different types of aluminium alloy, and several ways of making it into a hanger. Just as mild steel is different from cast iron. 

On this thread MMsRepBike (also a pro I believe) had this to say



> And as noted above, most all hangers from China are powdered metal and should not be messed with. I refuse to run such hangers on any bike I own, I always put a wheels manufacturing one on as soon as it gets built up the first time. So if you don't already have a wheels one or other cnc cut solid aluminum one, I'd put one on now just because.


What I can tell you from my own experience, is that the hanger in the photo (OEM Fuji), was mildly tweaked by myself - once, appeared to be OK, and then spontaneously failed while I was riding the bike, sending the RD and chain into the rear wheel with predictable results.


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## Migen21 (Oct 28, 2014)

So you have experienced one spontaneous derailleur hangar failure? Is it possible that that one unit was somehow defective? Or it was part of a bad batch?


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## Kerry Irons (Feb 25, 2002)

Peter P. said:


> They're not meant to be aligned because they're aluminum, which weakens very quickly if it's manipulated.


You're confusing misaligned with bent. A bent aluminum hanger most likely has been compromised. An out of alignment hanger can be straightened. Obviously there is some undefined boundary between misaligned and bent so some judgement is required, but unless it is visibly bent, the hangar can be aligned without issue.


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## bikerjulio (Jan 19, 2010)

Migen21 said:


> So you have experienced one spontaneous derailleur hangar failure? Is it possible that that one unit was somehow defective? Or it was part of a bad batch?


As per one of our other resident pros, MMsRepBike



> And as noted above, most all hangers from China are powdered metal and should not be messed with. I refuse to run such hangers on any bike I own, I always put a wheels manufacturing one on as soon as it gets built up the first time. So if you don't already have a wheels one or other cnc cut solid aluminum one, I'd put one on now just because.


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## TiCoyote (Jun 28, 2005)

The frame is a Specialized Tarmac SL3 Expert. It's CF. 

The chain is the correct length. However, it is worn to the point that it has 1/16" stretch over 12." I suppose this could cause it to fail to mesh with the teeth in the jockey wheel, but that's unlikely. 

It seems like aligning the hanger is probably good practice as part of maintenance, so I ordered the alignment tool from Art's Cyclery. It's backordered, but it was on sale for $60, and then I used the SAVE15 code to get another $9 off. 

I also ordered a Wheels MFG hanger from Art's. It was $16. Should I add a second one to the order, in case I break the first one adjusting it?


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## cxwrench (Nov 9, 2004)

TiCoyote said:


> The frame is a Specialized Tarmac SL3 Expert. It's CF.
> 
> The chain is the correct length. However, it is worn to the point that it has 1/16" stretch over 12." I suppose this could cause it to fail to mesh with the teeth in the jockey wheel, but that's unlikely.
> 
> ...


Very highly doubtful you'd break it aligning it but it's always good to have a spare.


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## TiCoyote (Jun 28, 2005)

I wanted to share the resolution of this issue. I was talking about the problem with the manager of my LBS, and he suggested that it was probably the chain, and he also gave me some tips on aligning the hanger. I also mentioned that it was a little sloppy in the center cog, and he said that was a further symptom of a worn chain. 

The chain and cassette had about 3k mi on them. I probably could have gotten more ouf the of the cassette, but I wanted to switch from 12-25 to 11-25 I replaced the chain and cassette, and the shifting improved about 90% and the dropped chain/pulley problem nearly disappeared. 

The derailleur alignment tool arrived, and I gave the hanger a few tweaks. The instructions said to align it within a tolerance of 4mm, and it was pretty much there already. Right on the edge of aligned/not aligned. The tool does have some play though, so I think it might be a little subjective and there might be a bit of an art to it.

Overall, I would say that the shifting is substantially improved, and I'm happy that I didn't break the hanger. Though I do have a spare one.


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## Peter P. (Dec 30, 2006)

Thanks for the update.

3k miles on a chain and cassette is nothing, so you shouldn't have had a problem caused by a WORN chain or cassette in the first place. I go at least triple that distance before I replace anything and never have shifting problems.

If however, the chain was slightly twisted along its axis (which is rare but which I've seen) then THAT could have been a cause of your problem. Usually you can spot it by sighting down the length of the chain, top or bottom, front to back, doesn't matter. 

Buying the spare hanger was a sound decision.


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## Lombard (May 8, 2014)

Peter P. said:


> Thanks for the update.
> 
> 3k miles on a chain and cassette is nothing, so you shouldn't have had a problem caused by a WORN chain or cassette in the first place. I go at least triple that distance before I replace anything and never have shifting problems.



The chain SHOULDN'T have worn out in 3K miles, but it is entirely possible that it did based on a number of factors like riding in rain, dirt and lack of lube in the chain.

As the saying goes, YMMV.


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## duriel (Oct 10, 2013)

Peter P. said:


> 3k miles on a chain . I go at least triple that distance


I assume your changing out every component at that point. or your not going very hard.


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## TiCoyote (Jun 28, 2005)

I used to change my chain every 1500 miles, and my cassette every 4500. Then, I read a lot of posts on this forum about how chains can last much longer, provided I keep it clean and lubed. I always lube and wipe it every few rides. I also use the Park chain cleaning tool if I do a rainy ride and/or the chain gets particularly dirty/gritty. I kept this chain on until 3k miles, and I was clearly having shifting problems. Just beginning to have them, but still. I measured the chain, and it had stretched by 1/16". I understand that this is the beginning of the time to think about replacement, and 1/8" is when you have worn your chain so far that you probably need to replace your cassette as well. By those guidelines, I imagine I could have gotten another 3k out of the chain. But how much does a chain cost? $20? $25? If I'm spending an extra $25 or $50/year to get better shifting, I'll take it. 

If you do a quick Google search for chain life and miles, you'll find that the general guidelines are 1500-3000 miles, but mileage alone is not a good indicator of chain wear. 

Furthermore, this article is really good: Bicycle chain wear explained - BikeRadar USA

"Some riders who don't put a lot of torque into their drive train will wear out the chain rollers before wear becomes apparent on a traditional chain checker. "Think of petite riders, or riders that may be of average size but spin a higher cadence," says Quade. "These riders will wear the roller down (side to side, not OD/ID) and the chain gets sloppy side to side but isn't 'stretched'.”"

At 140 lbs and with a cadence above 90, this might describe me pretty well. 

I appreciate all the advice in this thread. But I'm not sure why after I'm writing that I resolved the issue, I'm still getting posts telling me that I didn't, or that I resolved it incorrectly. I do not mean to offend anyone. I'm not trying to start a war. 

I mean, it's not like I'm asking for a comparison between chain lubes, or aero vs. weight, or tubeless vs tubes, or lube preference, or disks vs cantilever, or Coke vs. Pepsi.


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## velodog (Sep 26, 2007)

TiCoyote said:


> I used to change my chain every 1500 miles, and my cassette every 4500. Then, I read a lot of posts on this forum about how chains can last much longer, provided I keep it clean and lubed. I always lube and wipe it every few rides. I also use the Park chain cleaning tool if I do a rainy ride and/or the chain gets particularly dirty/gritty. I kept this chain on until 3k miles, and I was clearly having shifting problems. Just beginning to have them, but still. I measured the chain, and it had stretched by 1/16". I understand that this is the beginning of the time to think about replacement, and 1/8" is when you have worn your chain so far that you probably need to replace your cassette as well. By those guidelines, I imagine I could have gotten another 3k out of the chain. But how much does a chain cost? $20? $25? If I'm spending an extra $25 or $50/year to get better shifting, I'll take it.
> 
> If you do a quick Google search for chain life and miles, you'll find that the general guidelines are 1500-3000 miles, but mileage alone is not a good indicator of chain wear.
> 
> ...


I like root beer.


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## Lombard (May 8, 2014)

TiCoyote said:


> I appreciate all the advice in this thread. But I'm not sure why after I'm writing that I resolved the issue, I'm still getting posts telling me that I didn't, or that I resolved it incorrectly. I do not mean to offend anyone. I'm not trying to start a war.


What can I say? The important thing is that you found what works for you. Others have different experiences and have found what works best for them. That quote from the article is definitely some food for thought.

Nobody here is offended. Some just like to throw their anonymous blog weight around while others simply feel they know best and are just trying to help. We're just a bunch of schmucks who like to talk about bikes. Sometimes we get it right, sometimes not.

You forgot:

Cannondale vs. Trek
Shimano vs. SRAM


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## TiCoyote (Jun 28, 2005)

Thanks, Lombard. It's nice to see some humility and sanity on the 'net. And I totally forgot mechanical vs. electronic!


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## Peter P. (Dec 30, 2006)

duriel said:


> I assume your changing out every component at that point. or your not going very hard.


At that point, I replace the chainrings, cogs, and chain. Everything wears together so they seem to mesh well and shift fine. If I were to replace only the chain at that point, it would skip on every cog. Trust me, I know...


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## tigeo (Jun 6, 2010)

Interesting. Have this same issue on my Ultegra 6800 mid-cage. Had it on my 105 5800 short cage. The lower pulley actually get cock-eyed once in a while and I have to push it back into place. This caused the 105 to get ripped off. Not sure what is causing it but would suspect cross-chainring angle putting side-force on it.


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## Migen21 (Oct 28, 2014)

Cross chaining, while not ideal, should not pull a jockey wheel out of alignment unless something else is way out of whack.

Twisted derailleur cage, bent or twisted hangar, really terrible chainline/alignment issues, etc...


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## tigeo (Jun 6, 2010)

I blame the SCS spacing on my rear hub. Specy CruX.

Sent from my SM-G900V using Tapatalk


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## fronesis (Jan 22, 2014)

Just posting to give my own 2 cents of contribution to the debate staged here about aligning derailleur hangers. 

FWIW, I side completely with cxwrench. Over the past few years I have built up half a dozen carbon frame road bikes. EVERY single one of those had a hanger WAY out of alignment on a brand NEW frame. 

On each of those bikes I aligned the hanger with the Park Tool. I have yet to cause any damage to the frame or the hanger, and collectively those bikes have now had about 15k miles put on them – no problems. 

I DO have spare hangers just in case I need to replace one. But I'm confident that on the bikes I've dealt with, a brand new hanger would be just as much out of alignment as the one I was replacing. So the advice to "measure it, don't adjust it, but get a new one" doesn't square with my own experience.


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## GreasyBici (3 mo ago)

I just fixed my friend's bike, who was having issues with the chain falling off the jockey wheel, but in his circumstance the problem occurred while rear shifting. His problem was related to the rear derailleur not maintaining proper chain tension, and it was fixed by an adjustment of the B-screw, also known as body gap screw, which is the third limit screw that pushes on the derailleur hanger and adjusts the gap between the guide wheel of the derailleur and the teeth of the cassette. On my friend's bike, this screw came out too far resulting in lack of consistent chain tension. If you unscrew the b-screw all the way you can actually make the chain go totally slack, hard to demonstrate without a video. When there is enough slack in the chain, it doesn't get held on the guide/jockey wheel tightly enough to stay put and the chain falls off. His bike is a 1x, but I bet the problem could also occur with shifting a standard 2x or 3x front crank. Anyway, we tightened the b-screw just by 1 turn and you could see the tension returning to the chain and derailleur hanger and voila the bike was fixed!

I've seen numerous comments that the above issue could be due to a bent rear derailleur hanger or cage. Speaking from experience, I have ridden many bikes with significantly bent derailleur hangers and cages and never had an issue with the chain falling off the guide/jockey wheels (albeit the shifting was garbage), presumably because when the chain tension is appropriate, the chain is not given the opportunity to jump off. Not saying the cause of your woes cannot be due to a bent hanger/cage, but based on my experience I think the rear derailleur cage/hanger would have to be so far bent that the defect would be obvious on visual inspection. The reason a lot of people think this problem is because of a broken rear derailleur is because the problem will go away when you install a new derailleur and adjust the new derailleur's b-screw to the proper position.

Other possibilities to explain why a chain might be falling off guide/jockey wheels:

Chain line issues- I've worked on some bikes with chain line issues that were caused by incorrect bottom bracket/crankset combinations. This manifested primarily as sloppy shifting, and the chain would also fall off the crankset when pedaling backwards quickly. Theoretically this could also cause the chain to fall off the derailleur wheels. If this were your problem, your bike would have been performing poorly ever since owning it, not an acquired problem.
Bent, twisted, or sticky chain link.
Badly worn dérailleur pulley wheels. This means there is not enough tooth left to hold the chain on the pulley wheel. 
Worn chain. A badly worn chain will slip off the pulleys in this manner, sometimes. I imagine the chain would be so badly worn it would be jumping off the cassette under heavy pedaling. A mildly worn chain/cassette should not cause this problem.
Hope this helps!


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## Kerry Irons (Feb 25, 2002)

GreasyBici said:


> I just fixed my friend's bike, who was having issues with the chain falling off the jockey wheel, but in his circumstance the problem occurred while rear shifting. His problem was related to the rear derailleur not maintaining proper chain tension, and it was fixed by an adjustment of the B-screw, also known as body gap screw, which is the third limit screw that pushes on the derailleur hanger and adjusts the gap between the guide wheel of the derailleur and the teeth of the cassette. On my friend's bike, this screw came out too far resulting in lack of consistent chain tension. If you unscrew the b-screw all the way you can actually make the chain go totally slack, hard to demonstrate without a video. When there is enough slack in the chain, it doesn't get held on the guide/jockey wheel tightly enough to stay put and the chain falls off. His bike is a 1x, but I bet the problem could also occur with shifting a standard 2x or 3x front crank. Anyway, we tightened the b-screw just by 1 turn and you could see the tension returning to the chain and derailleur hanger and voila the bike was fixed!
> 
> I've seen numerous comments that the above issue could be due to a bent rear derailleur hanger or cage. Speaking from experience, I have ridden many bikes with significantly bent derailleur hangers and cages and never had an issue with the chain falling off the guide/jockey wheels (albeit the shifting was garbage), presumably because when the chain tension is appropriate, the chain is not given the opportunity to jump off. Not saying the cause of your woes cannot be due to a bent hanger/cage, but based on my experience I think the rear derailleur cage/hanger would have to be so far bent that the defect would be obvious on visual inspection. The reason a lot of people think this problem is because of a broken rear derailleur is because the problem will go away when you install a new derailleur and adjust the new derailleur's b-screw to the proper position.
> 
> ...


Given that this issue was discussed 6 years ago, I expect the OP has solved it by now. Just saying.


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## GreasyBici (3 mo ago)

Kerry Irons said:


> Given that this issue was discussed 6 years ago, I expect the OP has solved it by now. Just saying.


 Thanks for the input. Posting to help everyone else who has a problem like this. And who knows, if OP is still working on it, hopefully I just ended a 6 year struggle!


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