8 speed vs. 9 speed spacing (where is it)- Mtbr.com
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  1. #1

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    8 speed vs. 9 speed spacing (where is it)

    K I think I have a good one for you guys.

    If I wanted to take apart an 8 speed cassette and a 9 speed cassette and use the 8 speed cogs with the 9 speed spacers could I then run a 9 speed chain? What I'm wondering is where is the spacing difference between 8 and 9 speed. Is it 100% in the cog spacers or is there a difference in the metal cogs themselves?

    If you are curious why, I'm a trials rider that really only uses one gear. I run a very high end stupid expensive cassette, except for the one gear I use to ride trials. I found out I could buy individual cogs from cassettes for a lot cheaper than a full cassette. The problem is I run 9 speed and won't change. I can't buy a 9 speed 21 tooth cog. Only an 8 speed 21 tooth cog.

    Any help would be really appreciated. I called the 4 most reputable bike shops here and 2 said I would be ok, the only difference is the spacers, but the other 2 said no there is a difference in the cogs themselves and I'd get faster wear and possible other problems. So please only replies from people who really really know their stuff.

    Thanks a lot

    Brett McCullough
    www.biketrials.ca

  2. #2
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    Mostly the spacers

    f*nŠtik educated me few weeks ago stating that 9sp is 1.78 mm thick where 8 sp is 1.8 mm. I have measured both with my caliper as 1.8mm (I have only .05mm resoloution).
    This measurement is at the base of the tooth, the profile however is a liitle different between 8 and 9 and this may cause some performance differences.

  3. #3
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    The problem is I run 9 speed and won't change
    If you only use one gear, what difference will it make if you switch from a 9 speed drivetrain to an 8 speed one?
    ...he said "young man pay heed, you listen well to what i say, now there comes a time for a man to walk away"

  4. #4

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    Quote Originally Posted by lastminutebastrd
    If you only use one gear, what difference will it make if you switch from a 9 speed drivetrain to an 8 speed one?
    It would mean throwing out a perfectly good Sram X.O shifter and having to buy a new one. I have a weird deal and I don't run any shimano on my bike. I've tried every one of Srams chains for trials use which is very common to wreck chains fast. The best 8 speed chain they had was the pc51 which they no longer make. Even better than that is the pc99.

  5. #5

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    K I was doing some more thinking.

    How is it possible for a company to sell front chainrings that are 8 or 9 speed compatible but the rear cogs are not compatible? I don't see how it is ok to run an 8 or 9 speed chain on a front ring with no problems but you can't do the same on the cassette cogs (minus the spacing problem with the cassette spacers)

    Anyone have any input on this?

  6. #6

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    do you really thing that 0,02 mm will do a difference when a chain is about the less precise thing on a bike?
    Probably that the compagnie have a ▒0,01mm error on the machine so.... it won't change anything!

  7. #7

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    I'm a relative newbie, so what I say is far from gospel, but everything I've read/seen says a 9 speed chain is fine to use on an 8 speed cassette. Assuming what was said above about the size of cogs is correct, I would bet the tolerances of a chain are greater than the supposed difference between the widths of 8 and 9 speed cogs.

  8. #8

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    Quote Originally Posted by Island Ruffian
    If you are curious why, I'm a trials rider that really only uses one gear. I run a very high end stupid expensive cassette, except for the one gear I use to ride trials. I found out I could buy individual cogs from cassettes for a lot cheaper than a full cassette. The problem is I run 9 speed and won't change. I can't buy a 9 speed 21 tooth cog. Only an 8 speed 21 tooth cog.
    Maybe I am missing something, but why not just run singlespeed if you only ever use one gear?

  9. #9
    JmZ
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    If he's into trials

    Quote Originally Posted by frank n. beans
    Maybe I am missing something, but why not just run singlespeed if you only ever use one gear?
    Depending on the class he's running he may be required to have 'gears' in the back, even if they were never used. I think there was a company that did some carbon fiber 'gears' a while back to be effectively space-holders so that there were 'gears' on a trials bike.

    JmZ
    JmZ

    From one flat land to another.

    Advocate as if your ride depends on it...

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