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Shimano FW "slipping" under load on bumpy ground?

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Shimano FW "slipping" under load on bumpy ground?

Old 07-04-10, 04:02 PM
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Scrockern8r
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Shimano FW "slipping" under load on bumpy ground?

Hi All,
I do all maintenance, repair, and tune-ups for my bikes so I'm reasonably proficient at this stuff. However, this is a new one for me.
2005 Rockhopper w/sunrims, shimano hubs and a 9-speed cassette. All stock with the exception of a replaced FW(cheap, but new) unit installed about 100 miles of mild single track riding ago. Normally I ride in the seat and spin/grind the hills but am now trying to up the skills by standing up and mashing the pedals more. It took about 20 miles of more aggressive riding and now, on occasion, when I mash up the hills while standing, it feels like the ratchet in the freewheel gives out. At first, I thought I had chain slippage, but usually that has a longer sound that I can only describe as being similar to dragging a link chain on asphalt. Usually happens quickly but does have a little duration.
This issue sounds like a socket wrench ratchet pawl giving way. (with the added sounds of popping, spokes ringing, and me cursing because I just got pedal slap on the shin and bashed an elbow against a tree trying to save myself from falling down the hill I'm trying to climb!
Tried it with different gear selections and terrain. Skips while under load on bumpy ground. Is it possible for a fairly new FW to behave this way? I have never heard of this before.

Last edited by Scrockern8r; 07-04-10 at 04:06 PM.
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Old 07-04-10, 04:22 PM
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It still sounds like your chain is slipping....but one thing that is confusing me is that you say you bought a new freewheel, but you also say it's a 9 speed cassette... So, my thought is either your freehub body is toast (which has nothing to do with the cassette itself) or you've just got a wicked bad case of "new cassette/old, stretched chain" syndrome. And just as good measure, if you replace your cogs, you should always replace the chain too.
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Old 07-04-10, 05:00 PM
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Ahh,
Terminology clarification (I made this up on my own, so feel free to correct):
Hub = thingy to which spokes are connected.
FreeWheel = Ratchety thingy that clicks when I don't pedal. (I now will call freehub).
Cassette = Multi-pointed thingy that chain sits upon.

The cassette is separate from the freehub.
I've never had a freehub apart. The LBS assured me that I don't want to get into that and I would be better off buying a new one. (Reading some posts on BF reassured me as well).
Perhaps since the drive train is worn, and my riding style has changed, it could be the large front chain ring. The symptoms on only bumpy ground are at-odds with the type of sound I hear when it happens. I've had chainslip before, but the sound doesn't seem the same this time. Hence my posted question.
Maybe a better question: Can chainslip sound the same as freehub slippage?
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Old 07-04-10, 05:06 PM
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Well, yeah it can....it's easier to see if your chainrings are worn though. If the teeth are not a nice symmetrical shape, (also a dead give-away is if the chainring teeth are very, very pointed) you could be slipping on the chainring. And "lol" to your terminology....I completely get what your saying. It's all good. I do think that if the mechanics in your freehub body are going bad, you would have started to notice, and you would also have some issues even without being under an extreme load.
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Old 07-04-10, 05:12 PM
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Freehub bodies usually fail by either locking solid or freewheeling in both directions. They usually don't "skip". So to me it sounds like your chain is skipping on the new cassette (the collection of cogs that slip onto the freehub body). I'd fit a new chain as soon as possible.
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Old 07-04-10, 05:40 PM
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Originally Posted by redtires View Post
Well, yeah it can....it's easier to see if your chainrings are worn though. If the teeth are not a nice symmetrical shape, (also a dead give-away is if the chainring teeth are very, very pointed) you could be slipping on the chainring. And "lol" to your terminology....I completely get what your saying. It's all good. I do think that if the mechanics in your freehub body are going bad, you would have started to notice, and you would also have some issues even without being under an extreme load.
I'm cool with that. I've got about 500 miles of wet, mud (creamy AND crunchy), branch laden, puddle splashing miles of single track on this set of rings/chain. Lord only knows how many miles are on it from the previous owner. (Although it was shiny and none of the paint was worn off, anywhere at the time of purchase.)
I'll take a closer look at the drive-train wear. With the mileage, environment, and the change in riding style. It makes sense.
Now that I think about it, my prior experience was with BMX and road bikes used on pavement. In that environment, the cogs would have to be extremely worn by the time they failed and that would make it behave different while failing.
Riding MTB and thrashing over bumps would provide symptoms much earlier than riding on flat ground where the equipment can be extremely worn before slippage occurs.
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