ghost shifting

[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?

[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)?

[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.

[Miranda]

Kids' scooters, chewing cats (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.

[aicabsolut]

Kids' scooters, chewing cats (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!