Swap from GX Eagle (12spd) to GX 11spd - Cassette Depth Differences- Mtbr.com
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  1. #1
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    Swap from GX Eagle (12spd) to GX 11spd - Cassette Depth Differences

    2018 Kona Process 153 (27.5). Rear axle is 12 X 148 boost

    Just wiped out my 4th Eagle GX derailleur due to debris and I'm done with 12 spd. Have all parts to go 11spd. Staying with xD hub so using a 11spd GX cassette which allows me to use a medium cage Shimano derailleur giving me a bit more clearance and hopefully back to a more robust design. Also replacing chain and chainring along with Shimano 11spd shifter.

    I have a question related to cassette dimension differences.
    When I measure depth of the old 12 spd cassette its about 44mm. The new GX 11 cassette is about 41mm. To get these measurements, with cassette flat on workbench I put machinist rule through center and measure from bench up to outer face of smallest cog at the hub interface.

    When I flip the cassettes over, the 12spd cassette has about 6mm offset from outer edge of 50T gear to inner diameter where it fits over hub. The 11spd has about a 3mm offset. For this measurement I ran a straight edge across the back side of the biggest gear and measured from the straightedge to the face of the inner diameter of large gear where it meets hub.

    If you do the math:
    - 12 speed cassette...44mm - 6mm = 38mm depth at the hub
    - 11 speed cassette...41mm - 3mm = 38mm depth at the hub

    Looking for confirmation...the depth difference between the two cassettes is cancelled out by the offset differences and I DO NOT need any special spacer to go from 12 spd to 11 spd cassette.
    12 Santa Cruz Heckler
    18 Kona Process 153 AL/DL (27.5)...:thumbsup:

  2. #2
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    Seems a little suspicious.

    I know the internet is full of claims that the 12sp is a trail vacuum. I don't think I've picked up any more debris on my NX 12 speed than I have with my 2x10 XT derailleur.

    The distance to ground is similar enough that I can't see why the tiny difference would make sticks automatically hop into the chain.

    I wonder if it's because Shimano has their derailleurs tucked away a little more than the SRAM derailleur.
    With that said, I haven't taken notice of a GX derailleur (don't know anybody with one) to compare to the NX that sticks out to the side a mile.

  3. #3
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    Both 11 and 12 speed versions use the same XD driver. You would need a spacer if you wanted to use any of those cassettes on an XD-R ( road version ) driver - but that one is, as far, limited to RED and Force 12 speed AXS groups.

    So - your measurements are correct.

  4. #4
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    Quote Originally Posted by Forest Rider View Post
    Seems a little suspicious.

    I know the internet is full of claims that the 12sp is a trail vacuum. I don't think I've picked up any more debris on my NX 12 speed than I have with my 2x10 XT derailleur.

    The distance to ground is similar enough that I can't see why the tiny difference would make sticks automatically hop into the chain.

    I wonder if it's because Shimano has their derailleurs tucked away a little more than the SRAM derailleur.
    With that said, I haven't taken notice of a GX derailleur (don't know anybody with one) to compare to the NX that sticks out to the side a mile.
    Yeah I've given it over 1.5 years and 2,500 singletrack miles and that's enough confirmation the GX Eagle 12 spd is not for me. In 30 years of riding similar terrain I never had anywhere close to this many issues (including the one that came w/bike I've been through 3 of them and 2 hangers). Pretty sure I would have the same issues with upgrades to higher end 1X12 so that's not the answer either. I really don't 'need' 12 speeds...11 will be fine so I'm giving it a crack.

    I think you're right that it's a combination of the longer cage, the way the jockey wheels are configured, and the position/design of the derailleur body being more susceptible to hits for some riders.

    I'm going to install the 11spd setup later today and see how it works out.
    12 Santa Cruz Heckler
    18 Kona Process 153 AL/DL (27.5)...:thumbsup:

  5. #5
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    Quote Originally Posted by sturge View Post
    Looking for confirmation...the depth difference between the two cassettes is cancelled out by the offset differences and I DO NOT need any special spacer to go from 12 spd to 11 spd cassette.
    The freehub body interface is the same. No spacers are needed. Any difference in overall cassette width is because of the big cogs being dished/offset over the hub flange when you add the extra cog for 12spd.

  6. #6
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    Quote Originally Posted by sturge View Post
    Yeah I've given it over 1.5 years and 2,500 singletrack miles and that's enough confirmation the GX Eagle 12 spd is not for me. In 30 years of riding similar terrain I never had anywhere close to this many issues (including the one that came w/bike I've been through 3 of them and 2 hangers). Pretty sure I would have the same issues with upgrades to higher end 1X12 so that's not the answer either. I really don't 'need' 12 speeds...11 will be fine so I'm giving it a crack.

    I think you're right that it's a combination of the longer cage, the way the jockey wheels are configured, and the position/design of the derailleur body being more susceptible to hits for some riders.

    I'm going to install the 11spd setup later today and see how it works out.
    This is one reason why I was reluctant to go 12spd. I finally did when Shimano went 12spd and had a 10-45 cassette with a shorter cage derailleur. It's been solid, and there have been plenty of occasions where debris has been pulled into the lower pulley and the derailleur just spat it out.

  7. #7
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    I had a twig get bit by the lower wheel a few rides back....laid there horizontally pinched by the chain.

    I knew (thought) it happened, I stopped pedaling then stopped and sure enough a twig was there.

    Shimano 2x10.


    It's remarkable how small the Shimano body is compared to the SARM NX body.

  8. #8
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    'Backwards' 12spd to 11spd conversion complete and shifts like a champ. Hopefully this frequent debris issue is behind me and I'm back to normal.

    For those who may want to pursue this, I ended up with the following on an xD hub 12X148 boost bike that came stock with SRAM GX Eagle 12spd (10-50 cassette):
    -GX 11spd Cassette 10-42
    -GX Sync2 Chainring (bike came stock with 34T, replaced with 30T to keep similar 'low' ratio when combined with 11spd cassette)
    -SRAM 11spd chain
    -Shimano XT M8000 11spd derailleur
    -Shimano XT 11spd shifter w/cable
    -ProblemSolver adapter to allow SRAM Guide R brake lever and Shimano Shifter to share bar clamp.

    Total price just under $300
    12 Santa Cruz Heckler
    18 Kona Process 153 AL/DL (27.5)...:thumbsup:

  9. #9
    just ride
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    I did the same on my recent build, 2019 Pedalhead. I bought a used 11 speed XX1 shifter/cassette/RD for $200 and cleaned/greased/lubed it. 600 miles later, my drivetrain is still smooth and shifts flawless. Cheaper than Eagle and lighter.

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