converting from 9sp cassette to 8sp- Mtbr.com
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  1. #1
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    converting from 9sp cassette to 8sp

    I'm having a terrible time friction shifting the RD with a 9 speed cassette. I don't feel I need all those increments anyways so I want to replace it with an 8 speed cassette..

    What do I need to do? I'm thinking:

    Get an 8 speed cassette (Or convert the 9 speed to 8)?
    Get 8 speed chain ( do I need it?)

    What else am I missing? I have a 2012 Pugs complete so it's got the Shimano freehub. I believe I have to get Shimano branded cassette correct?

    thanks!

  2. #2
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    Quote Originally Posted by boogman View Post
    I'm having a terrible time friction shifting the RD with a 9 speed cassette. I don't feel I need all those increments anyways so I want to replace it with an 8 speed cassette..
    That's pretty much why they went to index shifting it just works better for most people. Practice should help, there was an art to it, a bit of over shift and then back off. In addition you may not find an 8 speed cassette all that easier to shift until you practice a bit.

    Quote Originally Posted by boogman View Post
    What do I need to do? I'm thinking:

    Get an 8 speed cassette (Or convert the 9 speed to 8)?
    Get 8 speed chain ( do I need it?)
    If you just delete one gear from your 9 speed cassette you won't change how hard it is to shift because the cogs are still at the same closer spacing. You don't need the 8 speed chain, the 9 speed chain will work fine on an 8 speed cassette. Well at least it does with index shifting.

    Quote Originally Posted by boogman View Post
    What else am I missing? I have a 2012 Pugs complete so it's got the Shimano freehub. I believe I have to get Shimano branded cassette correct?

    thanks!
    Shimano or Sram cassettes will work on the Shimano freehub.
    Latitude 61

  3. #3
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    Thanks.. I did more research as well an now thinking of doing a 7 speed cassette. I know that will require a spacer behind the cassette...

    I think another factor thats preventing good shifts is the 2:1 actuation ratio on the shimano RD.. It literally only takes a few milimeters of movement to shift between the higher gears..

  4. #4
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    Quote Originally Posted by boogman View Post
    Thanks.. I did more research as well an now thinking of doing a 7 speed cassette. I know that will require a spacer behind the cassette...

    I think another factor thats preventing good shifts is the 2:1 actuation ratio on the shimano RD.. It literally only takes a few milimeters of movement to shift between the higher gears..
    If I remember correctly, and People will let us know if I don't, the 7 speed cassette has exactly the same cog spacing as the 8 speed. They just made the whole cassette one cog wider on the 8 which is why you need the spacer to go back to the 7. Since the spacing is the same they will shift exactly the same.

    Why do you want friction shifting so badly? You can get thumb shifters that are indexed if thumbies are what you want to keep.
    Latitude 61

  5. #5
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    Quote Originally Posted by sryanak View Post
    If I remember correctly, and People will let us know if I don't, the 7 speed cassette has exactly the same cog spacing as the 8 speed. They just made the whole cassette one cog wider on the 8 which is why you need the spacer to go back to the 7. Since the spacing is the same they will shift exactly the same.
    Shimano 7/8 speed casette spacing is not identical, 5.0mm and 4.8mm respectivly. Campagnolo and early Sachs 8-speed both used 5.0mm spacing for 7 and 8 speed but shimano jumped at the chance for incompatability and planned obsolense .
    Sheldon Brown's Bicycle Frame and Cassette Spacing Crib Sheet

    I built my snowbike with a 7-speed casette, nice thing about narrower 7-speed casette is that the freehub body is also 5.0mm narrower so I was able to build the rear end with a perfectly dished symetrical spoke tension wheel that that is ofsett only 12mm instead of 17mm like a pug. For my riding, 7 speed casette is still plenty of gears.

  6. #6
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    Quote Originally Posted by boogman View Post
    I'm having a terrible time friction shifting the RD with a 9 speed cassette. I don't feel I need all those increments anyways so I want to replace it with an 8 speed cassette..

    What do I need to do? I'm thinking:

    Get an 8 speed cassette (Or convert the 9 speed to 8)?
    Get 8 speed chain ( do I need it?)

    What else am I missing? I have a 2012 Pugs complete so it's got the Shimano freehub. I believe I have to get Shimano branded cassette correct?

    thanks!
    For a casette with individual cogs (no alloy spider carrier) it is possible to disassemble the cogs and then you would need different width (8-speed) spacers to drop a cog and re-space to 8-speed. The thickness of 8 and 9 speed cogs is sliightly different (0.02mm) but close enough it would probably still even index OK as a 8 speed. One benefit of 7-speed casettes is that they use the thickest cogs so wear out slower.

    Note that it is also usually possible to transplant a narrower casette body from a older 7-speed casette hub onto a 8/9 speed hub if it works to your advantage to move the hub flanges toward drive side when using 7-speed or you can use a 9-speed casette with one cog dropped and run it as 8 of 9 on a 7-speed body.

  7. #7
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    Yeah I was also told be the LBS the 7 speed and 8 speed cogs are spaced the same.. so I just picked up a SRAM 8 sped cassette and will throw it on to see it improves..

    I want thumb shifters because the trigger shifters hurt my thumb.. I also heard those are difficult to use with gloves..

    I'm using cheap sunrace fiction shifters and don't want to shell out the money for thumbies and bar-ends right now

  8. #8
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    Dumb Question?
    What is the reason for removing a gear? I know its for clearance but why not just adjust RD to not shift that far?
    Please explain

  9. #9
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    So at least I learned something, Thanks GrayJay The remaining question is will a .34 mm farther apart spacing between the 8 and 9 speed cassettes be noticible in friction mode. Hopefully you will have better luck with thumbshifters than I did. The old Shimanos were stiff and I messed up both thumbs racing with them back in the day. I have to use Grip shift now as anything that requires pushing with my thumbs only works for a short while.
    Latitude 61

  10. #10
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    Boatracer.. One less speed reslts in greater spacing between the cogs. The idea is to allow easier friction shifting .

    Sryanak.. I have thumb pains from my prev trigger shifters.. The thumbshifter are a huge improvement.. In one direction, I just push the shifter with the side of my hand. Going the other way, i press down the lever with my hand or any combination of fingers or knuckles.. Very flexible and allows me to change it up.. No thumb pains now

  11. #11
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    cog spacing

    Here's a handy cribsheet detailing all the different Cassette / Freewheel spacings.

    Scroll down a little....

    Sheldon Brown's Bicycle Frame and Cassette Spacing Crib Sheet

    With this info, I've built many custom cassettes of varying speeds.

    RIP Sheldon Brown.

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