Bicycle Mechanics - loose cassette???
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06-04-03, 11:55 PM
hi. im looking for some second opinions on my bike problem. i bought the bike maybe three months ago (cannondale cx bike) and then changed the casssette a month ago to a 9spd shimano xt cassette. last week my chaine got caught on it because the whole thing had come loose and was wobbly. it was so loose i couldnt even backpedal because the chain wouldnt wind around it straight. so i figuired the bikeshop just forgot to tighten the lockring and no big deal i had them do it. then today i noticed my shifting being a little crappy and i thought to check the cassette to make sure it was still tight. it has a bit of play in it again so i brought it back to the shop. they tightened the hell out of it and it was still loose. so then they took off the cassette and checked the hub, which they greased up. the hub casing seemed to be a little loose but the hub itself was fine. the mechanic tried to put on a 1mm spacer but that wouldnt fit. he said that probably the hub has always been that way (before the cassette was changed out) and that all he could think of to do is to replace the hub casing, which theyd do for like $25 including a hub overhaul. but he suggested i ride the bike for a while and see how much the small amount of play in the cassette (after a retightening) actually affected my shifting. well a few hours of light riding later and the shifting hasnt slipped, but some gears make more noise than they used to.
any thoughts on this problem? seems weird to me. i dont remember the cassette being loose before but maybe it has been tht way since i bought the bike?
the mech thought that the hub itself didnt need to be replaced, only the casing. but that would be lame if they did change it out and the problem was still there...
06-05-03, 01:49 AM
The casing, commonly called the "cassette body," is held to the hub shell by a hollow tube-shaped bolt that's tightened/loosened by means of a 10mm hex key. One possibility is that this tube-shaped bolt simply isn't tight.
Another possibility is that the cassette body is fastened to the hub shell properly, but the cassette body's own bearing system has excessive play. If that's the case, and it's a Shimano, and you're the original owner, it should be possible to get a new cassette body under Shimano's warranty, provided you didn't abuse it or something. These can be taken apart and a shim removed to reduce their bearing play, but it's not something that I've seen in practice much.
If the cogs are all snugged together and don't have play among themselves, then that would point to one or both of these other possibilities. On the other hand, if the cogs are not being compressed enough to keep them snugged against eachother, even though the lockring is tight, then you are apparently up against the problem that your LBS tried to fix already.
At any rate, if you bought the bike new, then your LBS should have the green light to warranty the whole wheel if necessary (barring neglect/abuse). Good luck! :)
EDIT: I guess I'm assuming that this is, in fact, a Shimano rear hub. There are plenty of non-Shimano-brand hubs in use out there as well. More info on precisely what parts you've got wouldn't hurt :)
06-05-03, 01:14 PM
the cassette itself is brand new. its a shimano 9spd xt. the hub is a shimano 105. the bike is a few years old - 1999 model cannondale xr800. and i bought it used a few months ago (like the above post says). i dont have the bike in front of me but i think that it is the whole cassette that feels loose and not the individual cogs.
do you think that this problem could create other problems down the road? as long as my shifting holds and it isnt going to mess up my cassette or chain or wheel, then maybe i can deal with a little extra cogs noise...
the "cassette body" is the plastic cover on the hub itself? the lbs basically did a hub overhaul trying to figure out what was wrong. i am guessing that this would include the retightening of that bolt you suggested.
"These can be taken apart and a shim removed to reduce their bearing play, but it's not something that I've seen in practice much."
the lbs said they could replace the part of the hub they thought was loose without replacing the whole hub. they had some in stock and said it would cost like $25 with the labor.
i am going on a longish trail ride today. if i have any more problems i think i will just let them do whatever they think will solve it. -- unless someone on this forum tells me that their approach sounds weird or gives me some other advice.
06-05-03, 02:18 PM
The freehub body is metal, and yes riding with a loose cassette can cause damage. The working of the cassette can chew up the splines on the freehub body. This really is a bit of a mystery. I wish you lived close enough for me to take a look at it. It seems to me that a loose freehub body would be obvious to the mechanic. When you say a 1 mm spacer didn't fit, what exactly do you mean? With the spacer in place the lockring won't quite engage the threads so it can't be screwed on? What cogset are is the new cassette? This is a long shot and may even be impossible, but here it is anyway. Your bike is a few years old. Early freehub bodies would not take an 11 tooth cog. More current ones will. The difference is that the splines on more current models do not extend all the way to the end of the freehub body. This allows a little "ledge" to accomodate the smaller diameter of the 11. If you tried to put a cassette with an 11T on it, perhaps the lockring would screw on, but you would only be locking the 11 up against the end of the freehub, leaving the rest of the cassette a little loose, rather than tightening the whole cassette up against the hub itself as it should. As I said it may not even be possible to get the lockring on in this case. I am not sure when this design change came about, but even if it was pre 99 your wheel could be part of an older batch. If you want to read more about this to get a better understanding check sheldonbrown.com and read about cassettes and freehub bodies.
If this is the case, you could resolve it by using a 12T instead of the 11 or by replacing the freehub body itself, which is not expensive.
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