Chain Skip...redux.....
 

Hi all,

I was here a while back in regards to problem with chain skip on my '99 Hardrock (http://www.bikeforums.net/showthread...=#post14201679).

I'm waiting for the new chain (on exchange and hope it will be in this week) but I had a thought about what I was experiencing and thought I might be able to get a bit more help (or insight). I reinstalled my old cassette and chain and discovered after a few rides it had developed some skipping issues, as well (I know...In my last email of the above link, I stated I had completely solved the problem...alas, not to be :(

I adjusted the derailleur (Hi, Low and "B" limits) which seemed to help, but not eliminate, the problem. I remembered there was one other thing I did which is where I could use some expert opinions.

Some time ago, I had purchased a new set (2) of 11T plastic "cogs" for the derailleur and decided to install those this time around (the old ones were worn but had not given me any problems). I noticed a difference between the old and new set. The old top cog seemed to have quite a bit of play in it. Unfortunately, I have no idea if it had always been that way (never looked closely until I had put 13K+ miles on the bike), but while there are signs of wearing and use, the amount is way beyond what I think wear and tear should be (maybe I'm just being naive' here). Based on my limited knowledge, it looks like it was by design given how much bigger the diameter of the bushing "race" was compared to the bushing it rotated on. The new top cog is much like the bottom one (both old and new). The bushing "race" is much closer in diameter to the bushing.

This is the original Acera-X or Alivio derailleur from 1999. I'm wondering if this unit was designed with the amount of "play" for shifting reasons. Or, with the new cog in there, the adjustments have become much more critical? Do I need to go back to the old top cog?

Thanks in advance for any help.

Cheers...Steph

Sounds like the pulleys (cogs) might have been installedin the wrong location. The top one is supposed to be looser so as to have enough play to let the chain drop into the closest gear even if the derailleur isn't spot on, because it's never really perfectly aligned with the cassette.

My bad :( in the old set, it's very obvious the looser pulley is the top one in the setup. However, with the new set of pulleys, they appear to be interchangeable. Maybe I missed something....maybe I got a wrong set of pulleys? Maybe I need to wear better glasses when doing something like this...Hmmm...this may turn out to be a "D'oh!!" moment for me :( I'll go back and recheck the new ones (wasn't obvious when I did the replacement). Worst case, guess I can put back on the old ones until I can figure out what may have happened.

You did confirm that there is 1 pulley with at least a bit of play. Thanks.

Cheers...Steph

Just came back from checking out the pulleys. While it wasn't quite the "D'oh!!" moment I expected, I still should have looked closer (especially when I bought the pulley set a year or 2 ago). Both of the new pulleys are the same...no play in either one. Either I misread the description when I bought the set, or I got a bad package. I've put the old "loose" pulley (top) back on (left the new bottom pulleys) and will test the results on a ride tomorrow morning. I expect I will experience no skipping during my ride.

Now to see if I can find the correct top pulley....

Also, the pulleys are 10T (not 11T).

Cheers...Steph

Nothing is ever perfect...sigh

My ride this morning had some chain skipping, but it was so much less than before. I'm figuring with the adjustments I made to the derailleur before this crap started and that I have no idea if I put the old chain back on the same way it came off (inside-out, reverse flow direction, etc.), the little bit of skipping could be due to one, some or any of these things. However, I feel so much closer to solving this than before. A few readjustments to get it back closer to "normal" (whatever that might have been :( until my new/exchange chain comes in.....

Cheers...Steph

Might as well wait for the new chain.

I've recently had first hand experience with two causes for chains leaving the cogs.

One is a stiff link. As the chain rolls from the derailleur pulleys it shows a kink as it its the cassette cog, which will lead to the chain derailing. You can loosen the link with a chain tool or simply working it in your hands.

The other is a kink or bend. This often causes derailment from a chainring. To detect this, sight along the top of the chain as you turn the cranks slowly. A damaged chain will show a wave, twist, or kink as it passes from the cassette to the chainring. A chain showing this kind of damage needs to be replaced.

Chain Skip...redux.....
 

Thanks oldbobcat...

Kinking/tight link...one of the 1st things I checked for. Both new and old chain were very flexible thru out. I wish it would have been that easy.

Nah, this is definitely a wrong part (lower pulley) in the wrong place (upper pulley) due to wrong or bad pulley set (Someday I'll have to figure out where to get the right pulley....maybe just go for a new derailleur...tho, this one's still in pretty good shape...except for some wear and tear on the pulleys, that is). When the new chain started skipping, I assumed it was (in this order)...Chain, freehub, derail adjustment, chain, freehub....so it took me a few go arounds before I went back and checked the new pulleys. As I said in my previous posting, by then, the adjustments were made to be so sloppy just to see if I could eliminate the skip.

I just found out earlier this afternoon that Performance Bike messed up on my exchange (gave me a credit card refund instead) of the chain. Now I have to go back in and re-order...sheesh. The folks at the Performance Bike here in MV are usually friendly and helpful, but sometimes......hopefully I can get them to expedite it directly to me so I don't have to make another trip.

I can continue to ride the bike until I get the new chain (hopefully early next week) and reinstall it along with the new cassette. Until then, I'll have to climb hills in 6th gear.

Thanks again and cheers...Steph

Forget the pulley, that's not it. There was nothing wrong with the replacement pulley set you bought.

Shimano has this thing they call a Centeron-G pulley; the upper pulley is slightly narrower than its bushing, allowing some lateral float (if there's an actual diameter discrepancy, you're looking at wear).

The purpose of this is to allow for poor adjustment. It actually detract slightly from shift quality; some folks (myself included) are apt to intentionally swap the pulleys.

Chain Skip...redux.....
 

Kimmo,

Thanks for the input. I'll go back and double check things, but given the age of this derailleur setup (Alivio, 1999), I wonder if the way Shimano got the "play" back then was thru the diameter difference between the I.D of the pulley and O.D. of the bushing. I know the Centeron-G you speak of...I can see that embossed on the original "loose"/upper pulley. I don't remember either of the new pulleys having any reference to Centeron-G. I do remember one time that I pulled the original pulleys to clean them, put them back on swapped and found there was a width difference which caused one of the pulleys to bind.

Since you were kind enough to chime in, I have another question re: cassette "wobble". If I lift the tires off the ground and spin the rear tire so that it's not engaging the freehub (i.e. coasting, so to speak) I can notice a very slight wobble in the cassette and looks to coincide with wheel revolution. It's most obvious on the low (28T) gear and is prob'ly <1/8" total back and forth movement (on that gear). It's barely perceptible (if at all) on the 7th gear cog (which is where my chain skip has been occurring). I checked the axle and it's straight. Any thoughts on whether this is a bearing issue (recent greasing showed bearings and race in good shape and bearings all accounted for). I'm wondering if somehow a few spokes came loose and the hub is somehow misaligned...

Thanks again for the help....Steph

BTW - How are things in your hemisphere of the world? You must be getting near your winter. I visited eastern OZ (and NZ) over a decade ago and loved it (Spent a day in Melbourne before heading over to camp on Tasmania). Want to get back someday to see the western 1/2.

OK, just having come back from an early morning ride...everything is back to normal...before I tried to "repair" the chain/cassette.

Went up and down bridges this morning in 7th gear and not even a hint of chain skipping. So, here's the way I see it...2 problems, one extending the other. First, wrong pulley, wrong place. Second...putting the chain back on not in the way it came off (but then, I never expected to have to put the old chain back on). Now, just waiting for the new chain (which the LBF, Performance Bike, was kind enough to expedite directly to my house....they normally charge if not delivered to the store for pick up, and shipping was more than 1/2 the price of the chain....bless their customer service hearts :) Then I can reinstall both the chain and new cassette (which is where this all started....)

I discovered 2 other potential problems I will need to deal with at some point. The cassette "wobble" I mentioned above seems to be due to somewhat excessive play in the freehub (afterall, it's only got 18K+ miles on it ;) That may be a contributor to some of the chain shift issues that started me on this journey originally. The other is my rear rim looks like it has a very slight warp in it. Should prob'ly do something about that sometime soon.

Thanks again for everyone's help. It's amazing how just getting back to normal made me so happy this morning :)

Cheers...Steph

I actually ordered up a new jockey/Centeron-G pulley and received it today. I didn't even have to compare it next to the old one. The old one had waaaaaay too much play in it. Apparently I was not very good (as in never) about keeping the derailleur pulleys clean and oiled. I'll put on the new cassette, chain and pulley and I'm expecting the bike will shift like it was new. And I plan to be much better about maintenance ;)

Cheers....

Just a followup. I installed the new pulley. OMG :) - What a difference!!

Shifting is very crisp now. Some minor shifting issues I had going from 6th to 7th have pretty much disappeared. I'm still getting a very occasional chain skip here and there, but my guess is that's about better adjustment.

I took a closer look at the old jockey pulley. It definitely has some wear and tear on the race part (bushing didn't look too bad at all), but I don't believe it is really all that serious. My sense is at the time this bike (and derailleur) was mfg'd (~1999), this particular jockey pulley was designed with a lot of slop in it...side to side and around the bushing. It seems to me that that was the technology at the time. Maybe I'm wrong, but it doesn't seem like it.

The new pulley has only side to side play, and I think that "tightens" up the adjustment spec and reduces forgiveness for sloppy alignment. It also has a slightly different marking than the old one does.

Anyway, I'm happy to have found new life for my bike. :)

Again thanks to those who offered their insight.

Much cheers.....Steph