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Thread: Chain slips

  1. #1
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    Chain slips

    I bought my bike used which is a Trek Fuel 80. The previous owner said he just replaced the cassette and the chain. After I bought the bike, I found out the chain was slipping so I took it to the bike shop for a tuneup. The problem still occurred so I took it back to the shop with my friend. They tuned it 3 or 4 times, but still, the problem occurred with the chain slipping. Aftewards the mechanic did a pretty thorough inspection and found out that the bottom bracket was loose and needed replacing and the hanger was bent.After taking it to the Trek shop and replacing the bottom bracket and straightening the hanger, the problem is still occurring. The mechanic said the problem might be with the shifters, but I am not sure if that is the case.Can anyone give any help or advice? Thanks

  2. #2
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    Is it slipping or skipping ? Skipping is caused by mismatched chain and gears ,or bent teeth on the gears. Is it in every gear or only one? I'd look for a different shop if can't fix it by the second time.The "mechanic" should be able to tell you exactly what wrong and tell you how much it's going to cost to fix it.

  3. #3
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    Quote Originally Posted by rangeriderdave View Post
    ...I'd look for a different shop if can't fix it by the second time.The "mechanic" should be able to tell you exactly what wrong and tell you how much it's going to cost to fix it.
    Agree

  4. #4
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    Does it make any clicking noises when you pedal it in a stand(no load)? That would indicate a partially shifted condition aka adjustment. While rare, I have also seen underprofiled cassette cogs out of the box. It hasn't happened to me in a long time but it has happened a couple times. Check if it only happens in a particular gear(s) and then inspect accordingly.
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  5. #5
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    Yep, take it to another shop. A shop should be able to figure out if the problem is the chain, the cassette, or a front chain ring.

  6. #6
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    Whenever this sort of thing happens, I initially suspect a bent hanger. Regardless, it should have been fixed the first time. A new shop is definitely in order.

  7. #7
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    Quote Originally Posted by bikeRider88 View Post
    ...The previous owner said he just replaced the cassette and the chain...
    You need to replace the chainrings too. Middle and small, almost certainly not the big one. The chain that was on there before the previous owner replaced it was very stretched methinks.
    Don't you hate it when a sentence doesn't end the way you think it octopus?

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    Re: Chain slips

    Gummy cables on an older bike too. You can adjust, but if the cable is still stuck a bit and drifting, it won't matter. Way cheap to do yourself.
    Can't hurt to check for a mismatch. Check the chain model (stamped on link) check for xspd usage whatever you have.
    I don't want to bandwagon, but that shop...

    I have a Fuel 70, and I Love it. It's had some updates, but overall, it's been a good rig. Haven't broke it enough to justify replacing it.


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    Quote Originally Posted by zebrahum View Post
    You need to replace the chainrings too. Middle and small, almost certainly not the big one. The chain that was on there before the previous owner replaced it was very stretched methinks.

    I'm guessing this ^^, That or the seller wasn't being honest about the chain/cassette being new.

  10. #10
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    Quote Originally Posted by J.B. Weld View Post
    I'm guessing this ^^, That or the seller wasn't being honest about the chain/cassette being new.
    Could actually be better if everything is worn even.

    The cassette and eventually the chainrings get worn but a worn chain speeds that process. Once everything gets worn enough if you just change some things, like the chain or the chain and cassette in this case, problems like this can occur.

    But we're all just guessing over the internet. More input from OP is needed or it's just a shot in the dark.
    Last edited by theMeat; 04-29-2013 at 10:46 AM.
    Round and round we go

  11. #11
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    hey guys, I found out that the chain was not completely new... I found a segment that was repaired/attached.

    problem with chain skipping - YouTube

    I took a video of what I think the problem is. I have yet to find the source of the problem though. The bike shops have told me nothing...

    I hope you guys can help me find a solution!

    btw there was no shift in gear, just straight pedaling

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    I can't seem to watch the video, but the "repaired" segment is probably what's called a power-link. It makes taking the chain off easier. Some chains (like KMC and SRAM) come with it already attached.

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    Got the video to work. What it looks like is that your cable tension is slightly too tight, causing to to try and jump a little bit every couple revolutions. If adjusting it didn't fix it (the shop should have done that) dropping some lube on the cables or changing the cables completely should help.

  14. #14
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    Another problem is a tight link ,pedal backwards slowly with the bike upside down watching the chain go though the jockey wheels on the deraileur if the chain jumps or lifts in one place ,there is a tight link. Grab the chain in that spot and flex the chain sideways back and forth recheck though the jockey wheels.

  15. #15
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    Re: Chain slips

    I am big on the tight link theory as well. I had done all the rest, adjust, then clean, then new cables, clean, adjust, and still it would 'pop' every now and then, every few rotations. Turns out I had a stiff link, (from impact).
    Turn the cranks slowly and watch as the chain exits the derailleur to freewheel. The links should bend in. Look for a set of links that exits without bending. It could be tough to find. I have a thread on it somewhere with photo.

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  16. #16
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    A good bike mechanic would have noticed the bent hanger and a worn chain right away before doing ANYTHING else. these are easy to diagnose with basic tools. A good bike mechanic would have tested theories and test-ridden the bike until the problem was gone. that's what I do with every bike I fix- test ride until it's perfect.

    you have to check the entire system:
    frayed cable in the shifter
    gummed up or broken shifter
    frayed, worn, cracked, or worn out shift housing/ ferrules
    bent hanger
    worn chain
    crooked QR
    loose cassette
    loose hub bearings
    worn/ skipping freehub
    worn cassette
    worn rings
    worn/loose BB
    plus a few other culprits I can't think of.

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