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New cassette wobble I think causing spontaneous shifts

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New cassette wobble I think causing spontaneous shifts

Old 08-30-14, 04:57 AM
  #1  
natch
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New cassette wobble I think causing spontaneous shifts

I bought a used 1993 Raleigh Technium Pro last year, with Shimano hubs. But it had a 13-23 cassette which was just too arrow for me since I frequently do a lot of hills and needed the low end power for climbing. I changed it out for a new wider range 11-28 cassette. But it wobbles. I am not talking visual wobble during rotation. I can grasp the cassette and wobble it a few degrees while on the repair stand. I tried putting the original cassette on and it is solid. No wobble at all. It is not the tightening of the lock ring, as I tried really tightening it, and on the original, I don't even need to tighten it that much. I also notice that I get spontaneous gear changes when riding in the middle to the larger toothed rings of the cassette. (but never 11 or 28). So what is the problem and how do I fix it?
Note: I did search thru a few cassette wobble posts, but there are a lot, and after a few that don't seem to be quite relevant, I just decided to post my own.
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Old 08-30-14, 05:15 AM
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Do the cassettes have the same number of cogs? 11-28 very likely has ten, which is more than a 1993 bike would have (8?) unless the drivetrain has been updated in the past 10 years or so. The new cassette needs to have the same number of cogs as the old (and be compatible with the wrap range of RD).

Given the right number of cogs, the outer end of the cassette should protrude slightly beyond the free hub so that the threaded ring tightens against the cassette and not the free hub. If the cassette is loose on the freehub after tightening the ring, this isn't the case and a spacer is needed between the base of the free hub and the cassette.
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Old 08-30-14, 06:02 AM
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The gear count matches at 7. The original cassette had a spacer, but it was between 13 & 14 and gave it the proper spacing between the gears. It is thin, however. A mm or 2. Maybe I can try putting it at the bottom, behind the biggest gear, closer to the center of the hub to see if that allows me to properly tighten the cassette onto the hub. Obviously, I'd then need to adjust the rear derailleur, but that's not hard to do. Do you think that might work?
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Old 08-30-14, 07:15 AM
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Number of cogs match, which is good. Perhaps someone with a better memory or more recent experience with these cogs can weigh in, but lacking that I'd carefully examine and measure (using calipers) both cassettes to ascertain exactly where and how they differ with respect to spacing and how they sit on the free hub, determine on which end it would be appropriate to place a spacer, and how thick the spacer needs to be.
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Old 08-30-14, 08:51 AM
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It ain't supposed to wobble.

Yeah, I know. Duh.

Dunno what's wrong, though I know something is. Once the more experienced regulars get here you should get some good feedback.
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Old 08-30-14, 10:31 AM
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My 7-speed road cassettes have the thin spacer, but from what I remember the spacer goes between the 5th and 6th cogs at the top of the stack of cogs that are screwed or riveted together, NOT between the 6th and 7th cog (smallest).

Is it possible that your new cassette is missing the spacer? What brand is it? If the spacer is missing, it would be hard to tell by looking, because the difference is so minor without it (other than the cassette not tightening). What about taking the spacer from your old cassette, and using it with the new cassette in the place that the spacer goes in the old cassette?
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Old 08-30-14, 12:39 PM
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Have you tried searching on your cassette's model number to find an exploded diagram? Usually the model number followed by "PDF" will give solid hits. Then it will be clear which spacers go where. After the cassette is correctly assembled inspect the assembly to ensure that the cassette overhangs the shoulder of the freehub a couple of millimeters. Then torque the lockring correctly (it takes more than you might think) and check for play.
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Old 08-30-14, 01:03 PM
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Stack the two cassettes side by side on a table. You should be able to tell fairly easily where the problem is.
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Old 08-31-14, 11:10 AM
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The 11 tooth small cog may not be compatible with your freehub.

Search Sheldon Brown for 11 tooth sprocket, or Hyperglide-C
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Old 08-31-14, 04:09 PM
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I think I may have solved the problem. It may be that the 11 tooth sprocket isn't compatible, without a little finageling. I did put the spacer (actually not really a spacer as much as a little ring that fills the space between the littlest cog and the next bigger one fitting over 3 pins) onto the freehub 1st, or at the back of the cassette, closest to the center of the wheel. The reason there was a wobble, was because the smallest 11 tooth cog, unlike the 13 tooth smallest cog on the other cassette, was not slotted all the way thru. rather it had a cap arrangement on the outside that limited how far it could be mounted onto the freehub. So it wan't really meeting the inner "solid" part of the cassette when it was mounted. There was a gap. Thus the wobble. By bringing out the main body of the cassette the mm or two that the spacer provides, the smallest 11 tooth cog was able to snug up against the main body of the cassette without bottoming out on its cap to the slots. Take Note: the locking ring that came with the old hub, did not have enough thread to seat with newer cassette. But the newer cassette's lock ring did have more thread (it was longer) and could extend deep enough to lock the cassette into the hub. I still have to make some minor adjustments on the derailleur now and test drive it, but I think I have the fix, finally. Does anybody see any pitfalls with this "solution?"
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Old 08-31-14, 05:26 PM
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I would modify the freehub body. See the hyperdrive-C link in my previous post.
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Old 08-31-14, 05:28 PM
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Natch,
If you haven't already done so, having moved from 13 to 11, you will want to check your chain length to ensure that RD still has tension when in 11 & smallest front chainring.

This isn't a solution to your cassette wobble. But nevertheless, should be checked when changing to a lower teeth last sprocket.

Last edited by UltraMonkey; 08-31-14 at 05:32 PM.
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Old 08-31-14, 06:04 PM
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You may want to evaluate if that 11 tooth sprocket will do you any good. I replaced a 7 cog 13-26 with a 13-30, and got more useful gear combinations in the midrange. So far, have not wanted smaller than the 13, but the 30 gets used. The -30 will bump the jockey wheel on my original RD if not careful.

Last edited by wide45; 08-31-14 at 06:18 PM.
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Old 09-01-14, 04:39 AM
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Looks like they are saying, adding a spacer will do the trick. So it looks like I did the correct thing. Is that what you mean by modify freehub body?
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Old 09-01-14, 05:06 AM
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I think you are right that the 11 might not be such a useful gear to have added. I'll probably go Simano 13,15,17,20.23.26.30 next time. There is even a 13,15,17,20,24,29,34 available, but that might be too choppy at the easy pedaling range. Part of my modifications on this last bout of "doing my own maintenance" was to climb hills easier. The original bike components were the standard 42-53 Shimano 105 crank & a 13,14,15,17,19,21,23 cassette with a short armed 105 RD. I now have an 11,13,15,18,21,24,28 with a Shimano LX Delore RD that has a long arm (chain length is fine now) and a Shimano Ultegra Crank triple A52-B38-A30. I think I finally have this bike in decent shape and more hill friendly gearing.
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Old 09-01-14, 06:33 AM
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I'm sure you checked for clearance with the chain on the small sprocket, so using the shim should be good, particularly if you may be going back to 12 or 13 tooth.

I have that same 105 53-42 crank, and RD. I really don't want to go to a triple.

Last edited by wide45; 09-01-14 at 06:36 AM.
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