ghost shifting

[sundial]

I just finished a ride in which my chain was busy chatting with the 50T cog and the derailleur or chain or cassette decided to play switch and slip when I used 34T and the 3rd highest gear :mad:

I've measured the chain and it's not stretched out. I had the front derailleur adjusted because I was losing the chain between the 50 and 34 cog, whether I was shifting up or down. Now the rear is jumping from the 2nd and 3rd highest gear even though I've adjusted the rear derailleur. The teeth on the cassette do not look worn and I don't see any light between the chain and the cassette.

I have a SRAM OG 1070 11-28 cassette. Is this the nature of the beast? Do I need to replace anything? I have had this bike for a year now and put about 4000 miles on it. Thanks in advance.

[aicabsolut]

What do you mean by "jumping"? Do you mean the chain feels like it's skipping on top of the cog or is the chain trying to jump between cogs and not settling on any one cog?

The first is "skipping," and the second is "autoshifting."

Skipping: http://sheldonbrown.com/derailer-adjustment.html#skipping

Autoshifting: http://www.sheldonbrown.com/autoshift.html

Alternatively, your indexing may be off. Does it happen such that you have a hard time shifting up or down into that problem cog? If so, then it's an indexing issue. If you can shift fine but then it starts acting up under load, then it may be one of the other problems.

If indexing improves things some but not enough or not for long, then check the condition of your cables. Any obvious damage to the cable or housing? Is it really dry under your bottom bracket? Try lubing the cables under the BB. If nothing works and you're certain it is not a chain wear problem, then you might need to replace your cables. Since you had some issues recently with the FD as well that sounds like a cable tension problem, my guess is that your cables are just getting too old and need to be replaced. That's not surprising at the year mark with the mileage you've got. DA cables might last a bit longer (because they're thicker) but it's probably a good time to change them, particularly if they are not Dura Ace cables.

[DebW]

If you have 4000 miles on one chain, then it's time to replace it. 2000 miles is a more reasonable replacement time. You may have to replace the cassette as well as the chain to avoid skipping.

[sundial]

What do you mean by "jumping"? Do you mean the chain feels like it's skipping on top of the cog or is the chain trying to jump between cogs and not settling on any one cog?

Both. I don't have any problem shifting, but the chain wants to ghost shift over the cassette. Thanks for sharing the links and I'm going to meet with the lbs mechanic and see what we can do to fix the problem.

I guess a new chain and cassette is a small price to pay.

[aicabsolut]

I had my shifting go all to hell when my cables quit on me. Eventually, it would get where I'd lose pretty much all tension on the cables and I couldn't get into any cog in particular. The large end of the cassette was the worst, because that's where you need the most tension on the cable. After 6500 miles on one cassette and chain, it never got that bad. I did have issues in just a couple of cogs when, after a really mucky ride, I cleaned my bike too well and had too much friction going on with the cables under the BB. The chain and cassette were fine. Lubing the cables fixed that.

4000 miles is probably near the end of the chain's life. If the chain checker is still good for sure (on the smallest measurement side), then I'd look to the cables. It could ultimately come down to being time to replace everything. Your cassette might still be fine--they can check that with the chain whip thing. Chain and cables replacement would be the cheapest way to start.

[ridebikeme]

If indeed you have 4000 miles on your chain/cassette, then take Debs advice and replace both. Do NOT replace one without the other; you will simply cause even more problems. It does sound like a cable tension problem, although with that many miles on your drivetrain, I would replace the chain/cassette and have your LBS check the cables and the housing that feeds into your rear derailleur.

[Mr. SR500]

Chain life is all about maintenance, if it's cleaned and lubed it can last for 10's of thousands of miles. Sounds like it just not adjusted properly. I would also have the mechanic check chain length, maybe removing a link or 2 could help. Unless you rarely lube your drivetrain, your cassette and chainrings should be fine. You should go thru 2/3 chains at least per cassette.

[Miranda]

Ok, I'm totally humble :o here to answer, but since I am having and had this same issue with my mtb I'm putting my vote in for "cables" as the problem source.

The mtb was (and still is) doing the same thing. My kids somehow have the habit of throwing their scooters into the bike rack... which leads me to cursing and preying the bars out of my mtb rear wheel:mad:...

I came here and searched my problem and geeked out good ole Sheldon. For srue I thought it was the derailer. I didn't feel confident enough to adjust on my own, and E-ed one of my guy bike pals w/pics. Needing my bike for the holiday w/e camping trip, I loaded her up to the shop. The tech (and my guy pal wrote back by time I got home) both said "cable stretch"...

The tech didn't even take if off the vehicle rack. He showed me how to adjust it at the bars to tighten the cables. Sure enough it got better. Rode it on a flat at home, was ok. Then when I was climbing hard on the trail... bam, right back. Worst time to happen of course. I about bit it :eek: in the steep drop off as the bike didn't perform as expected.

So, my guy pal says that bar adjustment is for "micro" stuff. The piece towards the back end of the cable is for "macro", bigger adjustment. He said try turning it one way... if gets worse... then go the other until it quits. I'm lucky my suv bike rack makes a great work stand. For ME, I just don't feel confident enough to know when to stop turning the adjustment knob. I guess if you have turned and turned the thing... well, the cables have had all the adjusting they can take before replacement.

[aicabsolut]

Cables don't actually stretch. That's a myth. What happens with new cables is that over the first few weeks, they will become more squarely seated in the housing and ferrules due to use (tension), and so then the prior indexing set at installation is then making the cable too slack. So the usual thing is to tighten the cables by turning the barrel adjuster counterclockwise (towards the frame) a bit until shifting returns to normal. In one rare case, the mechanic actually installed my cable too tight, as I discovered when turning the barrel counterclockwise made things worse. If you start running out of room on the barrel adjuster and things are still not right, then the cable is nearing death, or you need to do a big overhaul if it's new. Either way, it helps to loosen the barrel adjuster again (so you have room to re-index). Then grab the cable under the down tube and yank hard sideways to make sure everything is seated properly. Then use a clamp or fourth hand tool to hold the end of the cable, loosen the pinch bolt, take up the slack in the cable, re-tighten the bolt, and then redo the indexing using the barrel adjusters.

If the cables are near death, then you may find they are spontaneously loosening. Re-tightening the cable may only be a temporary fix. Shifting problems will then spread across the cassette. You may also notice fraying of the cables at the ferrules. You should also check to see if the housing has been damaged.

If the issue is just the chain, then skipping only on a specific cog or two suggests that those cogs are unduly worn and the cassette will need to be replaced too.

Because you are experiencing autoshifting as well as skipping, I think there is something going on with your cables, particularly if you're starting to notice hesitation when you try to shift one direction (or both). One explanation is that you've got too much friction going on around the BB. More likely with the age and mileage, I think it's time to replace the cables. That costs like $5, plus new bar tape. Even if that doesn't fix your problem, it isn't going to hurt.

[ridebikeme]

Taking links out of a chain is a very temporary fix.... the issue with chain wear is that the bushings start to wear(people used to say that the chain stretches )when that happens the chain sits differently on the cassette . Removing links does not help this.... my theory is once you have problems fix it the correct way. There are all sorts of temporary things that you can do, but they are simply a band aid and generally don't last long. The problems by doing these temporary fix(s) become bigger and you tend to have more of them. If someone wants a bike to shift well in all gears, then the best solution is to replace the chain and cassette. Although with the sounds of this bike... as others have mentioned I would check cables/housing as well. We can talk these problems all day... but if you aren't able to do the repairs yourself then take the bike to your local LBS ... you'll feel much better when you can ride and you aren't thinking about the bike and its poor shifting.

[sundial]

I won a new cassette and chain today. ;) The chain was 1/16 inch off but enough for me to want a new one. Also, it *seems* like the SRAM cassette wore kinda fast despite the fact that I kept the cassette and the chain super clean and lubed. I'll see if this one does any better. I kind of get the impression that Shimano wears better in the long run but we'll see.

Thanks everyone for your tips and recommendations. I'm off to do a chick ride in the morning and I'll see how the shifting goes.

[wackyjacky1]

My bike is doing the same thing. It likes to do it when I'm climbing a hill -- goodbye, momentum!

Took it to the LBS yesterday, where they adjusted the cables, and the front and rear derailleurs. On my ride to work this morning, it did the same thing, with the added bonus on my not being able to shift into the smallest chainring. Erk!

Today he checked out the cassette and said it seems fine. He went ahead and replaced the chain, even though it wasn't showing any wear. (Heck, I've only put about 200 miles on the bike.) On the ride home from the LBS, I had one incident where it feels like the chain is skipping a tooth on one of the cogs. (What I mean is, it "feels" like it's shifting on its own, but is staying on the same cog.) Annoying! Guess I'm taking it back to the shop tomorrow...

A question: My cats have chewed off the little caps on the cable ends. Because of this, on the rear derailleur, one wire in the cable has unwound itself from the others. (Note how the little one, Erin, is helpfully pointing out the problem for the photo.) If it's a cable issue, is it possible that this could be the source of the problem? :confused:

[aicabsolut]

Well that is definitely not good for the cable. It may not be catastrophic though.

Does the skipping (since the bike isn't trying to jump into other cogs, what you described is called "skipping") happen more on certain cogs? If so, which ones? Does it make a difference if you have shifted down into the problem cog or up?

I don't know why the LBS messed with your front derailleur. That seems to have just gotten your shifting even more screwed up.

Try loosening the FD cable (turn the barrel adjuster on the frame clockwise) and see if that lets you shift into the small ring. You may need to really loosen it. Then, once you're in the small ring, see if the chain is rubbing the cage. If so, then it could also be they set your lower limit wrong. Loosen that limit screw (the one closest to the frame) until there's no more rubbing. If you get rubbing now in the large chainring, then you probably loosened the cable too much. Shift to middle ring, tighten cable, then check up and down shifts again.

As for the back, what other information can you give? In addition to my first questions, is it slow (a hesitation) to shift in either direction (inward or outward)?

[Miranda]

Kids' scooters, chewing cats :eek: (oh, and cute cat, btw)... gheez, don't these lil dharlings know we need our bikes to shift right? ;)

aicabsolut... thx for the info on cables. I read this a while back in the thread and didn't pop any more in as it looked like things got resolved, but what a wonderful education. I love TE for this reason. My "cable stretch" term was from the shop owner that sold me my road bike. That place ended up being just a crooked mess for me that never lived up to what they promised:(. It's made me tainted when I go anywhere... sorta like the used car sales lot.

I have been thinking about switching out my spd pedals to eggbeaters on my mtb. Think I'll just leave it at the pedal purchase shop and see if they can resolve the problem with the shifting.

[wackyjacky1]

Does the skipping (since the bike isn't trying to jump into other cogs, what you described is called "skipping") happen more on certain cogs? If so, which ones? Does it make a difference if you have shifted down into the problem cog or up?
Now that I've looked at that Sheldon Brown info, I can say that I have experienced both skipping and autoshifting. What happened this afternoon was skipping.

It only seems to happen when I'm in the smallest chainring, am in the 3rd or 4th cog, and am grinding up a hill. The skip or autoshift will occur well after my last gear change.


I don't know why the LBS messed with your front derailleur. That seems to have just gotten your shifting even more screwed up.
He fixed it today. Front derailleur is fine now.


Then, once you're in the small ring, see if the chain is rubbing the cage.
Had a lot of chain rub after he messed with the front derailleur, but it was fine after he readjusted it today.


is it slow (a hesitation) to shift in either direction (inward or outward)?
Shifting is nice and crisp. The problem only occurs under load, as when I'm going up a hill. It doesn't happen during or right after a shift. It happens well after the last shift, making it totally unexpected when it does occur!

Your advice is sure appreciated! :)

[DebW]

Quite often you'll get more skipping with a new chain and old cassette. We'll typically replace the chain, then ride the bike to check for skipping under load, and replace the cassette if necessary.

[aicabsolut]

Quite often you'll get more skipping with a new chain and old cassette. We'll typically replace the chain, then ride the bike to check for skipping under load, and replace the cassette if necessary.

Yeah, if it's shifting fine and then you run into problems under load, it's likely your cassette. You might also want to take some WD40 and really lube up where the cables run underneath your bottom bracket as well as inside your shifters. That ought to get rid of any unnecessary friction on the cables that could cause the autoshift to occur when the frame flexes. You might also want to get the shop to check your rear derailleur and derailleur hangar. Make sure the hangar isn't bent. Finally, if you *still* have problems, make sure there isn't a lot of lateral play in the derailleur indicating that it's getting worn out and needs overhauled or replaced.

[aicabsolut]

Kids' scooters, chewing cats :eek: (oh, and cute cat, btw)... gheez, don't these lil dharlings know we need our bikes to shift right? ;)

aicabsolut... thx for the info on cables. I read this a while back in the thread and didn't pop any more in as it looked like things got resolved, but what a wonderful education. I love TE for this reason. My "cable stretch" term was from the shop owner that sold me my road bike. That place ended up being just a crooked mess for me that never lived up to what they promised:(. It's made me tainted when I go anywhere... sorta like the used car sales lot.

I have been thinking about switching out my spd pedals to eggbeaters on my mtb. Think I'll just leave it at the pedal purchase shop and see if they can resolve the problem with the shifting.

You're welcome. I started having some shifting problems last weekend and wound up snapping my rear cable out of the blue. Luckily, it happened when I went to tune up the bike after I had climbed up the mountain back to the house where I was staying. I needed my large cogs to make it up that beast. I certainly would have been walking if I'd been stuck in the little cog with a broken cable.

[emily_in_nc]

I am getting ghost shifting or skipping (I don't think it's actually changing gears, it just sounds like it) when I'm going downhill in my small cogs in back (middle crank in front) on my mountain bike. Not under load. Shifting is fine. The cassette is only a year old and a good one (XTR). I don't ride a lot of miles in a given year, so I am sure I haven't worn it out yet. Does this sound like a chain problem? Bent rear derailleur?

One more thing -- I notice it at the beginning of a ride, but then it seems to stop. Odd.

Any ideas appreciated -- thanks much! :)

[aicabsolut]

Are you in those gear combos at any other time? If so, do you get the same problem happening? It could be more of a cross chain / chainline issue than something that would manifest under load. But it may get worse under load, if you use those gears on flatter ground. I don't know why it'd go away, though. Hmm. Do you get any front derailleur rub?

[wackyjacky1]

Thanks for the info & advice. I was too tired to stop by the bike shop after work on Fri. and on Sat., so I'll ride over there on Monday and see what they can do.

Mucho appreciado! :cool:

[emily_in_nc]

Are you in those gear combos at any other time? If so, do you get the same problem happening? It could be more of a cross chain / chainline issue than something that would manifest under load. But it may get worse under load, if you use those gears on flatter ground. I don't know why it'd go away, though. Hmm. Do you get any front derailleur rub?

No, no front derailleur rub at all. I normally use only the middle front ring on my MTB unless the terrain gets really steep, and I was not aware that any gear in back was considered cross-chaining when used with the middle crank of a triple. Perhaps I should be shifting to the larger ring in back when using the smallest cogs in back? I only use those smaller cogs for descending and on the flats. The riding I do is very rolling, so it's much easier to stay in the middle cog all the way than try to go back and forth in the front for short distances, but if that is what is causing the problem, I can definitely give it a try.

Thanks!

[aicabsolut]

It could be. Looking at how to test the indexing for triples, you tighten the cable such that you don't get rubbing in the middle ring / large cog combo. I've seen a bit of rubbing going on in the middle ring / small cog combo a lot (it's my friend's favorite gear).

The chain is pretty slack at this point, though not as much as in small ring/small cog. I wonder if you're getting symptoms of a stiff link. What happens if you put it in the small ring/small cog (you may have to use some FD trim to keep the chain from grinding around on the FD). You could also just try trimming when in the middle ring / small cogs in case you do get some slight rubbing when the frame flexes.

I'm pretty perplexed, though.

If it's trying to autoshift in the small cogs, can you tell which direction? Does it try to jump up or down? You might want to recheck your upper limit.

The first place I'd look would be to see if there's a stiff or bent link or if your derailleur hangar is bent.

[emily_in_nc]

It could be. Looking at how to test the indexing for triples, you tighten the cable such that you don't get rubbing in the middle ring / large cog combo. I've seen a bit of rubbing going on in the middle ring / small cog combo a lot (it's my friend's favorite gear).

The chain is pretty slack at this point, though not as much as in small ring/small cog. I wonder if you're getting symptoms of a stiff link. What happens if you put it in the small ring/small cog (you may have to use some FD trim to keep the chain from grinding around on the FD). You could also just try trimming when in the middle ring / small cogs in case you do get some slight rubbing when the frame flexes.

I'm pretty perplexed, though.

If it's trying to autoshift in the small cogs, can you tell which direction? Does it try to jump up or down? You might want to recheck your upper limit.

The first place I'd look would be to see if there's a stiff or bent link or if your derailleur hangar is bent.

Thanks for all the great ideas, aicabsolut -- I'll check it out (to the best of my ability) this weekend when I have a bit more time.

I did ride tonight and noticed the skipping sound while in the two smallest cogs in back and middle in front, pedaling on the flats. I shifted to the large ring in front, and the problem stopped. That may mean it's not a bad chain link, I'd think.

From then on, I always shifted to the large ring when I needed to use higher gears, and things were fine.

I'd still like to get to the root of the problem, though, in case something needs adjusted/changed.

Thank you!

[aicabsolut]

Well a stiff link would be most noticeable in the smallest ring (according to Sheldon Brown). Honestly, I have no experience with bad links other than when my BF broke a link on a brand new chain, but then I could see one plate sticking out, making a click sound each time it went through the wheels in the derailleur.

That it shifts and rides fine in the small cogs while you're in the big ring does tell me that your H limit screw is set right and that your cassette is probably ok.

I'm thinking that maybe your chain is probably getting too old for you to be cross chaining in the middle ring, even if it is harder to really cross chain on a triple. Next, instead of shifting up to the big ring, try using a little FD trim when you want to use the small cogs/middle ring combo (like a 1/2 shift with the front shifter). See what happens.

[emily_in_nc]

I'm thinking that maybe your chain is probably getting too old for you to be cross chaining in the middle ring, even if it is harder to really cross chain on a triple. Next, instead of shifting up to the big ring, try using a little FD trim when you want to use the small cogs/middle ring combo (like a 1/2 shift with the front shifter). See what happens.

I'm going to measure my chain for stretch too.

I am not sure I can do a half-shift in the front. These are mountain-bike shifters (XTR rapid-fire). I could always half-shift on my road bike with either Shimano or Campy shifters but haven't noticed that I can do that on my mountain bike. :confused:

Thanks!

[aicabsolut]

Oh yeah, I guess I was just thinking road bike. I don't know what kind of trim you'd have on those if any.