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  1. #1
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    Will an 8 speed rear derailleur work with a 9 speed shifter and cassette?

    Can an 8 speed shimano deore rear derailleur be made to work with a 9 speed shifter and cassette? I recall a lbs employee saying its possible to make a 9 speed derailleur work on a 10 speed set up awhile back. True? Are either of these possible?

  2. #2
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    Yes (within the respective brands) and no, not reliably, respectively. 7/8/9 all use the same cable pull, 10 speed in both brands is unique.

  3. #3
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    Sure no problem at all, now the 10speeds are different than the older models and require more cable pull..

  4. #4
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    So I take it its all a matter of derailleur adjustment and mating it to a 9spd shifter and cassette? How would I go about making the adjustments to make it work? Are there any complications to worry about? Wschruba mentioned that there may be reliability issues.

  5. #5
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    I ran an 8 speed Alivio RD on a 9 speed XT / XTR drive train as a stop gap after I kopped a trail snake and bust the cage on the XTR one. I needed a lightly longer B screw to clear the 34T cassette and one of the limit screws (think it was the high) was right at the edge but other than that it worked surprisingly well - one thing I would say is make sure you have a chain stay protector - the RD spring is not as strong as the Shadow RD's and you will get chain slap over even moderate bumps - it occasionally dropped the chain when very rough so I wouldn't go DH or anything with that set up but for XC or general trail riding it's OK.
    BTW you can use Shimano 9 speed MTN RD's with 10 speed road shifters but not 10 speed mtn shifters.
    Last edited by SimpleJon; 04-12-2013 at 11:32 PM.

  6. #6
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    Quote Originally Posted by CyclesnIPAs View Post
    Can an 8 speed shimano deore rear derailleur be made to work with a 9 speed shifter and cassette? I recall a lbs employee saying its possible to make a 9 speed derailleur work on a 10 speed set up awhile back. True? Are either of these possible?
    Hmm, which model is it exactly as I don't remember Shimano Deore ever being specifically an 8-speed derailleur... Nevertheless it doesn't really matter as an 8-speed derailleur should work with 9 speeds.

  7. #7
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    I didn't want to start a whole new thread, but have a question. I have been debating going to a 10 speed cassette, and go from a 8x3 to a 10x2 setup, but maybe I can get most of what I am looking for with a 9x2 drivetrain

    I have a old XTR M900 rear free hub and derailleur
    It looks like I have a 12x28 cassette

    I was thinking maybe I can go with a 9 speed 11x32 or 11x34 cassette, new shifters, chain and keep my current hub, and derailleur

    here are some pics, let me know if I am right about having a 12x28 cassette, will my rear derailleur work if I go to a 9 speed cassette, and any other suggestions

    Also would only use the rear 32, or 34 tooth gear when I am using the smaller front sprocket

    Will an 8 speed rear derailleur work with a 9 speed shifter and cassette?-xtr28a.jpgName:  xtr12.jpg
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Size:  55.2 KBWill an 8 speed rear derailleur work with a 9 speed shifter and cassette?-xtrhub.jpgWill an 8 speed rear derailleur work with a 9 speed shifter and cassette?-xtr.jpg

  8. #8
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    Those guys above your post did that. You wouldn't gain much by changing since 8s cassettes are also available with 32t, just a little closer gear ratios.

    Great, clear pics. The other side of the teeth are the side that wears in the first pic. Can't really tell if it's worn or not from that angle. The way some people test them is install a new chain and see if it slips.

  9. #9
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    Quote Originally Posted by Dons Stang View Post
    I didn't want to start a whole new thread, but have a question. I have been debating going to a 10 speed cassette, and go from a 8x3 to a 10x2 setup, but maybe I can get most of what I am looking for with a 9x2 drivetrain

    I have a old XTR M900 rear free hub and derailleur
    It looks like I have a 12x28 cassette

    I was thinking maybe I can go with a 9 speed 11x32 or 11x34 cassette, new shifters, chain and keep my current hub, and derailleur

    here are some pics, let me know if I am right about having a 12x28 cassette, will my rear derailleur work if I go to a 9 speed cassette, and any other suggestions

    Also would only use the rear 32, or 34 tooth gear when I am using the smaller front sprocket
    Yes, your XTR derailleur will work with 9 speed shifter and cassette. 8 and 9 speed Shimano RD's are for all practical purposes interchangeable.

    From what I have seen written, the XTR M900 rear derailleur has a listed max cog size of 32t. That said, I have exceeded max cog size by 2 teeth on several Shimano and Sram RD's, and was always fine, and everything I read says it is generally not a problem. You might just need a longer B-tension screw (though I never did).

    Yes, it looks like you have a 12-28 cassette, but if in doubt just count the teeth.
    15mm is a second-best solution to a problem that was already solved.

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