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New chain AND cassette, now skipping (a lot)
#1
I just had the bike shop install a new cassette and chain. (I've been looking around online all evening and similar threads are all about only one or the other part getting replaced and problems resulting.) I've had this Giant mountain bike 12+ years, street use only, supposedly originally made for a bike messenger company so it had 9 gears in back, no parts replacements to speak of this whole time. Partly the reason for the new parts now was how old everything was, and mostly because I was starting to experience more and more skipping in the past month or so.

The new pieces should match each other (Shimano HG chain - box says ok for 9-speed, and Shimano SLX HG80 Cassette 9-Speed). If they aren't in fact a match, please set me straight! The chain and gears are aligned just fine. No problems with the front gears ("chain rings"?). From standstill especially or even while moving, placing load on the pedals is resulting in skipping over 90% of the time. Have tried using gears 4 - 8 without success, but normally I start from standstill with 5, 6, or 7.

The bike shop tech said the he set the chain length to "standard" length. He adjusted a screw making the chain "wrap" more underneath the cassette, but it made no difference. And even looking closely we couldn't see any part of the gears where the chain didn't mesh.

Any place we haven't looked? Any ideas?
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#2
If the setup is correct otherwise, the chain rings could be worn. If the bike has a lot of kms on it without any parts being replaced (as indicated by your description) this is the likely source of your problem. Get a new crank set.
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#3
Is your chain a CN-7701, CN-HG93, CN-HG73 or CN-HG53

Theses are the only ones working with your cassette... Also as said earlier, take a look at your chainrings or see if your chain is properly mounted
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#4
(12-27-2011, 10:45 AM)bobtravers Wrote:  Is your chain a CN-7701, CN-HG93, CN-HG73 or CN-HG53

Theses are the only ones working with your cassette... Also as said earlier, take a look at your chainrings or see if your chain is properly mounted

Thank you. I'll have a look at the precise chain product number. I left the box at the shop.
I'm not sure what problem to look for with the front gears. As I said, I don't see any problems or anything different with them. How are the front gears relevant to the slipping in the back?
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#5
Take a look at this Website so you can check for worn chainrings:

http://www.utahmountainbiking.com/fix/chainrng.htm

Also, is there some broken or bend teeth on chainring?

Your problem should be chainrings since you explained earlier that slippage was getting worst by the time
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#6
Thank you. I see your reasoning and had a look at the page on chainrings. I left my bike at the shop yesterday, so I'll ask about the chainring wear next time.
So, if I understand you correctly, even though there is no slippage, no apparent problem in the front, (i.e., the slippage with the old cassette and especially now with the new cassette and chain is in the back) the problem is highly unlikely to be in the back?
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#7
I don't think it's the chain rings. More likely the rear derailleur is not aligned. Ask the shop to check the alignment. Even better, have them get on the bike and try it! Or have them ride next to you while you try it out before you leave the store.

The other thing to check is wear of the jockey wheels in the rear derailleur.

The chain should say the model/part number if you look at it very closely.

I guess it's possible the cassette might be slipping too.
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#8
At this point, the shop said they had 2 people look to figure out what was going on, and they saw the slippage start on the front gear. Since I've had the thing for a long time, and in the interest of time, I am following their recommendation to change the front chain ring (actually they said just the middle one because of how much torque it normally receives/makes, but I asked for the middle and biggest ones to be replaced since I use both of them and the timing seems right).
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#9
(12-27-2011, 10:21 PM)AndrewB Wrote:  I don't think it's the chain rings. More likely the rear derailleur is not aligned. Ask the shop to check the alignment. Even better, have them get on the bike and try it! Or have them ride next to you while you try it out before you leave the store.

The other thing to check is wear of the jockey wheels in the rear derailleur.

The chain should say the model/part number if you look at it very closely.

I guess it's possible the cassette might be slipping too.

Misaligned rear derailleur doesn't cause slipping, it's more a misshifts...
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#10
Any new 9 speed chain should work with any new 9 speed cassette.
In this case I would go for the front chainrings or slippage in the rear freehub.
Does it do it on all the front chainrings or only one?
Or maybe the freehub pauls are worn?
Ride hard or ride home alone!
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#11
I tend to agree with Joe-W as you mentioned nothing has been replaced in 9 years of use. Sounds like the front chainrings are excessively worn and with a new chain you will see where the chain sits UP off the chainring instead of down into the recess between the teeth. I have seen this many times and with a new rear cassette and chain, the chainrings are about the only other thing that can cause slippage. If the pawls in the rear hub are worn you will get a sensation where the crankset will start to spin partially before engaging the rear gears. Easiest way to check the pawls is to remove the wheel and feel how the cassette engages when rotated forward. It should feel even.
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#12
Hello , every time I have a slipping problem I change the chain cassette and front chain rings ,it seems to be the only way ,of course it should not be that way and it wouldn't if the cassette and front gear rings where made of higher tension steel ,but is all about money isn't it .
Patrick .
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