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Thread: Help

  1. #1
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    Help

    I recently bought a Truvativ GXP crankset for my bike, and althought it's a huge upgrade, it threw the rest of my drivetrain off. There seems to be a lot of unnecessary friction on the cassette and rear derailleur. Anyway, the only thing I haven't replaced on my bike would be the f & r derailleur, cassette, and seat/seatpost. Can someone tell me what derailleurs would work with this crankset and what size cassette as well. Thank you in advance.


  2. #2
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    Probably just need to adjust your front derailleur, maybe the rear as well. Try here http://www.parktool.com/repair/byregion.asp?catid=53. What was your old crank setup? Should be able to use just about any cassette and derailleurs you want to, with the limitations set by your shifters (not your crankset). How worn is the chain? The cassette? Time to change them out or just itching to spend money?
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  3. #3
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    Lol, definitely enjoy upgrading, but I do think it's time to upgrade them. The chain isn't too bad, probably could stay if need be, but the derailleurs are POS and are the only thing irritating me when I ride. Right now I'm at 24 speed (8x3) and would like to keep it that way. My question is, I've noticed a few different teeth counts on a bunch of different cassettes, so which cassette (for MTB) and tooth count should I go with? Should I just count the teeth I have now and get as close as possible to that? And since I am spending the money, I want the derailleurs to be of good quality for MTB, so what would you suggest?

  4. #4
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    If you're happy with the gearing with your current cassette, match it (count the teeth; the number of teeth might be stamped in each cog, too). If you need a lower gear now's the time to address it. If you replace the cassette it's probably best to replace the chain at the same time. Since you have Shimano now, stay with it unless you're in the market for shifters too; can't usually go wrong with Shimano's LX level or above.
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  5. #5
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    Awesome, will do, thank you. As for the derailleurs, I wanted the X.0, but my LBS said that it was a long cage, and I needed a medium cage, so would an x.9 work? And for front derailleur, any in particular that you think is better? More reliable, stronger, better material?

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    Quote Originally Posted by mchale20
    Awesome, will do, thank you. As for the derailleurs, I wanted the X.0, but my LBS said that it was a long cage, and I needed a medium cage, so would an x.9 work? And for front derailleur, any in particular that you think is better? More reliable, stronger, better material?
    Don't know why they say you need a medium cage if you're running three rings plus a cassette, long cage is usually better; X0 comes in both versions. You've got a long cage now by the looks of it. X.9 rear derailleur requires SRAM shifter to work. Front derailleurs have little magic in them, they either work or they don't, they don't need to be particularly "strong".
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  7. #7
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    Ok cool, thank you again. Now say I did get a new cassette, would I need a particular chain length, or type. Like, I see how it says so and so cassette works with this length/type of chain. Would the distance between teeth between front and rear differ?

  8. #8
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    Quote Originally Posted by mchale20
    Ok cool, thank you again. Now say I did get a new cassette, would I need a particular chain length, or type. Like, I see how it says so and so cassette works with this length/type of chain. Would the distance between teeth between front and rear differ?
    The chain comes more than long enough, you shorten it to fit your bike. Try this http://www.parktool.com/repair/readhowto.asp?id=26. Get an 8 speed chain.
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  9. #9
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    "There seems to be a lot of unnecessary friction on the cassette and rear derailleur."

    Sounds to me like a chain length issue. Does the new crankset have larger/smaller chainrings?
    I bet all you need is a new chain adjusted to the correct length.
    Looking at the picture of the rear derailleur, it looks like it might need the B-tension screw adjusted as well. But it's hard to tell and probably not what you're complaining about.

    Cassette and rear derailleur doesn't really matter, especially if it was working fine before you changed the crank. You determine the number of teeth on the cassette cogs based on the gearing you want/need, in conjunction with the chainrings.

    Front derailleur could be an issue - look up the number of chainring tooth difference specification and compare to your cranks chainrings - but probably not. And again wouldn't explain the issue you describe.

    So probably a chain length problem.

    Just curious, who installed the crank?

  10. #10
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    LBS. Everything seems to be find up front, it's just the rear that seems to be off. What is a B-tension screw, and how would I adjust it? And how do I tell what length my chain should be?

  11. #11
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    Quote Originally Posted by mchale20
    LBS. Everything seems to be find up front, it's just the rear that seems to be off. What is a B-tension screw, and how would I adjust it? And how do I tell what length my chain should be?
    Read the Park tutorial on derailleur adjustment and chain sizing and you'll find out...
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  12. #12
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    Before we go there, why don't you explain in more detail what "There seems to be a lot of unnecessary friction on the cassette and rear derailleur" means.
    It also might be helpful if you took some pictures of what you're trying to describe. This way we can better understand the problem.

    Or, the other option is just take it back to the LBS and have them fix it - which would probably be the quickest, least headache for you...

  13. #13
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    Quote Originally Posted by chuckji
    Before we go there, why don't you explain in more detail what "There seems to be a lot of unnecessary friction on the cassette and rear derailleur" means.
    It also might be helpful if you took some pictures of what you're trying to describe. This way we can better understand the problem.

    Or, the other option is just take it back to the LBS and have them fix it - which would probably be the quickest, least headache for you...
    I think I'll do that. Save me some time and effort, and I hope they just suggest I get a new derailleur and cassette and chain . I guess I just enjoy upgrading, lol. But I may do a before and after for you guys, just so you see what I was talking about.

  14. #14
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    Quote Originally Posted by mchale20
    I think I'll do that. Save me some time and effort, and I hope they just suggest I get a new derailleur and cassette and chain . I guess I just enjoy upgrading, lol. But I may do a before and after for you guys, just so you see what I was talking about.
    Rather than just spend money for a problem that may not exist, just learn to fine tune your gear...or spend money if that makes you happy (not like I've ever done that ).
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  15. #15
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    Agreed, and that's definitely something I've done in the past, but I know I would be better off with a new derailleur and having my LBS install and tune it would be the easiest option.

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