Wobbly Cassette...?
 

Bought a new Mavic wheelset with Specialized hubs some time ago. Slapped a used Shimano 10spd cassette on it and experienced some skipping in shifting. Took to the shop and they pointed out that the cassette didn’t rotate exactly parallel to the wheel. It’s orbit was tilted away from center. My mechanic tried to shim it and suggested I needed a new cassette. I just bought another used one and the same thing is happening. Me thinks it’s not the cassette. Have any of you’s had this happen before? Does it need a new hub body?

Should learn to provide pertinent details:

1. 105/Ultegra Cassette or Dura Ace
2. Steel Freehub Body or Alloy Freehub Body
3. Size of Shim Tried So Far?

=8-)

It's quite common to have some cassette wobble, but it's quite rare to be troubled by it. Either yours is way bigger than usual, or the skipping isn't related to the wobble.

I think you might be needing a spacer somewhere. Provide pertinent details as requested by post #2.

One other possibility:

This is a loose ball generic cassette hub "relabelled" as Specialized...

Generic hubs - freewheel and cassette type alike - are often found machined off center on one side - or both. This will result in a one-sided wobble, two-sided wobble and if lucky - a rotating rise and fall along the axis.

Even then, while an eyesore - should not have an effect on shifting.

Shifting alignment/mechanical issues for rear derailleurs are usually caused by hanger misalignment, wear mismatch between cassette and chain, and set-screw mishaps.

But get back to us anyway on the earlier details requested...

=8-)

I have a Specialized rear wheel on my bike, and any cassette, including the SRAM that came on the bike will wobble when freewheeling. If the cassette is being driven by the chain, there is no visible wobble. The wheel is getting replaced soon, but I haven't noticed any problems due to it.

I think this is freehub related. If the inner freehub bearing fails the freehub will "tilt" on the axle. This will cause the cassette to "wobble" as it rotates. It will cause people to think it's "skipping" when it's really "ghost shifting" as the cogs move in and out of alignment with the derailleur.

You cannot feel if the bearing has failed by pushing/pulling on the cassette. Remove the wheel and cassette. Rotate the freehub. If it rotates concentric to the axle, then the bearing has failed. You will need to disassemble the hub and replace the bearing. Depending on how long the damage has existed and how extensive it is you may need to replace the internal bearing spacers.

I am going through this exact issue with a Sun-Ringle Dirty Flea hub at the moment.

The replacement cassette I just put on is a used Ultegra.
I'm going to assume the freehub is alloy, but not sure.
The shop mechanic put the shim in, I don't know what size it was.

I haven't ridden these wheels in several months, but my initial complaint was skipping between about the 7-8 cogs. The mechanic first thought it might be a bent hanger, but that checked OK. He was getting frustrated by not being able to smooth out the shifting when he noticed the wobble, he put a shim in it and suggested that I might need a new cassette. I just put on this used Ultegra and when you spin the wheel will looking straight down over it, you can see the cassette weave in and out as much of an eighth of an inch. These wheels are supposedly new Mavic CXP-22 laced to generic Specialized branded hubs. It's almost as if the freehub is not centered on the axle.

The side slop of those top pulleys is supposed to correct for minor wobbles ..

though cramming those 10 cogs back there makes a narrow gap between each

compensating and error get closer together..

1. Verify that the rear wheel is properly dished - using NOT the arms of the dishing tool for reference - but rather USE center-point-on-locknut for reference.
2. Then if wheel turns out to not be dished - get it dished THEN fix the hanger alignment.

If at that point fiddling with barrel and screw adjusters doesn't fix the problem - the issue is elsewhere. I.e., housings, brifters, bent derailleur, cassette and chain wear mismatch, ferrules, etc...

Even wobble of an 1/8 of an inch will have minimal impact on shifting performance.

=8-)

The wobble could be due to the freehub body. Could also be due to the hub body being bent Could also be the cassette is too worn out, and that's what's causing the chain skip.

The easiest to check would be the cassette. Swap in one you know is good and see if it still skips. If it does, ruling out the hub as the culplrit will be trickier.

BL

I'll try this one more time then let it die. I don't have any other cassette to try, but this is the second one that has had the same result. If you look straight down over the cassette between the large cog and the spokes, you can clearly see some of the hub grooves on one side while the other side is snug. It's almost as if something is keeping the cassette from completely seating on one side. However, when I've examined the free hub, there doesn't seem to be anything that would cause this. I thought about trying to slide on a spacer first, then the cassette to see if that would force the cassette become flush with the freehub. Although, it seems like that may cause some other complications.

"you can clearly see some of the hub grooves on one side while the other side is snug"

That definitely warrants a very close look at the freehub splines, freehub stop, and each individual cassette cog and spacer...hopefully it's just some kind of burr or machining error that can be filed away - and not a bent cog or something.

=8-)

It is probably the hub, I have had three different cassettes on that same OEM Specialized hub and they all wobble. I've tried just tightening the lockring finger tight, and also torquing it down, no difference. The hub/freehweel assembly is junk.

This has been my suspicion all along. Would replacing the freehub correct it, or could it be more serious?

rothenfield1

Don't start going in circles guy...

As already stated...the wobble is unlikely the cause of shifting issue...

1. Verify hanger alignment WITH properly dished wheel.
2. Then tackle adjustments, barrels, housing, cables, ferrules, derailleur body straightness, pulley's, etc.

The wobble is found on most if not all cheap OEM hubs and has little or no effect on shifting.

However if you see visible defects in the freehub splines, cogs, spacers, freehub stop, then by all means it doesn't hurt to clean them up if possible.

Having flush spacers and cogs under a tight lockring with no gaps or play is always a good thing. It prevents damage to the freehub body - especially alloy ones.

=8-)

Thanks mrrabbit, I'll cool my jets for now. This bike build is coming along very nicely. Just need brakes and a chain. I'm hoping to have the chain & cable it up in the next few days. Then can put it on the stand and try the shifting. Never seems to be the same on the stand and in the field however.

That is very true. Very rare is the person who can dial in today's index systems such that they work as well in the field as in the shop. Usually this person is someone who can practically dial in ANY index system within 15 minutes - almost as if they can do it in their sleep. These kinds of folks are work every penny you pay 'em. I'd say they are worth more than a wheelbuilder. People will tolerate wheels slightly out of true - but I've found that customers simply don't tolerate poor shifting. It really does irritate folks to no end.

If you ever are in San Jose, see Chuck at Bicycle Express in downtown San Jose. Even though I do a fair job - I never hesitate to have him check over my setups anyway for a second opinion. He never fails to do an adjustment or two which seems to take whatever shift hesitation was left in my work and eliminate it entirely.

=8-)

Pics.

Otherwise, all I can believe is that you failed in your examination.

If your freehub body is ally, but has normal-depth splines, there's a chance the cassette is getting hooked up on damage from previous use (normal HG splines are too shallow for ally; the cogs dig in).

Using a single cog, find out why you can't slide it all the way home on the splines.

Found the culprit! Took the cassette off and found that the thin ring inside the large cog had broken into pieces along one side, thereby not allowing the cassette to lay flat. I removed it and reinstalled the cassette. Problem solved. Hopefully that ring is not important.
http://i700.photobucket.com/albums/w...assette001.jpg

1. Good
2. Ride!

=8-)

Based upon what you found, this is THE most disturbing part of this whole thread...

New issue, let's see if anyone is still watching this old post. With that little ring gone, the cassette snugs so closely that to reach the large cog requires the derailer nestle within a hairs breath of the spokes. I hoping to finally ride tomorrow, 'cept calling for rain. Seems like one big bump in the road might put the RD unto the spokes. Anyone used a spacer at the back of the cassette to push it out a little away from the wheel?

Get a replacement for the one that got damaged...the original was probably 2mm thick?

=8-)

You really don't want to take chances here....derailleur in the wheel does one helluva lot of damage...

Thought so as well, thanks Rabbit. Don't know where to get that internal ring. Do you think that adding a spare cog spacer would work. Or, would that be too big to secure the lock ring?