Interpreting Shimano Hub Dimensions
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  1. #1
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    Interpreting Shimano Hub Dimensions

    Hi there!

    I'm building up a set of wheels with Shimano XT M8000 QR hubs. I *think* I'm reading the dimensions correctly, but I'd love a second set of eyes on this from the wonderful members of this forum.

    Here are the Shimano pages:

    https://bike.shimano.com/en-US/produ.../HB-M8000.html
    https://bike.shimano.com/en-US/produ.../FH-M8000.html

    For the front hub, it says this:


    Flange diameter (mm) 52.8 / 51.4
    Flange distance (mm) 60.4
    Internal grease sleeve X
    O.L.D. (mm) 100
    Offset (mm) 5.8
    P.C.D (mm) 44 / 41
    I interpret the PCD to be left (NDS) 44mm, then right (DS) 41mm. I see the flange distance of 60.4mm to be the measurement between flanges, center to center. Then, using the offset, I divide 60.4mm by 2 to get 30.2mm, then offset it by 5.8mm = 24.4mm, from left flange to center. The right flange to center would then be 60.4m minus 24.4mm = 36mm. I think "flange diameter" might be the measurement all the way to the outside diameter of the flange, just not sure what to do with that.

    For the rear hub, they give:

    Flange diameter (mm) 52.8/53.8
    Flange distance (mm) 57.4
    Internal grease sleeve X
    O.L.D. (mm) 135
    Offset (mm) 6.6
    P.C.D. (mm) 44/45
    I do the same, 44mm for left PCD, 45mm for right BCD. 57.4mm/2 - 6.6m offset = 22.1mm, only this time it's offset to the right where the freehub is, so 22.1mm is right flange to center. Then that's 35.3mm to the left flange.

    Does this all sound right?

    When I threw these measurements into multiple spoke calculators with DT Swiss 533d hubs (ERD 564mm), I get:

    Front wheel:

    • Left spoke length: 274.1
    • Right spoke length: 275.9


    Rear wheel:

    • Left spoke length: 275.3
    • Right spoke length: 273.8




    Any input would be much appreciated!

    Thank you!

  2. #2
    'brifter' is a lame word.
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    Flange diameter has always been center-to-center. Leave it to Shimano to come up w/ acronyms and terms that are unique and proprietary. Normally you need flange diameter, center-to-flange for each side, number of spokes and crosses, and if you're really anal, spoke hole diameter. Everyone uses these dimensions.

    I have no idea what flange distance, offset, and P.C.D. refer to. It would be so much easier if they'd just do what the rest of the world does. I think the problem is that they employ entirely too many engineers.
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  3. #3
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    Quote Originally Posted by cxwrench View Post
    Flange diameter has always been center-to-center. Leave it to Shimano to come up w/ acronyms and terms that are unique and proprietary. Normally you need flange diameter, center-to-flange for each side, number of spokes and crosses, and if you're really anal, spoke hole diameter. Everyone uses these dimensions.

    I have no idea what flange distance, offset, and P.C.D. refer to. It would be so much easier if they'd just do what the rest of the world does. I think the problem is that they employ entirely too many engineers.
    ^^^This.^^^

    And let me add this. Do NOT trust ANY manufacturers specs. Do your own measurements for everything!!! I have found errors in manufacters specs which would have given me the wrong spoke lengths.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  4. #4
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    Thanks Lombard. I do have the rear hub, and I measured it and it seems to match. Trouble is I'm not exactly sure how to get a precise measurement from center to flange. Any tips on that? Or should I measure from the outside where the hub ends before the axle to the center of the flange when looking down from the top?

  5. #5
    'brifter' is a lame word.
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    Front hub: It's a 100mm OLN so measure from the center of one flange to the center of the other...half that is your center-to-flange.

    Rear hub: It's a 135mm OLN so the center is at 67.5mm from the end of the axle...either end, doesn't matter. NOT the end of the part that sits in the dropout, the end of the axle itself. I use calipers to do all of this. I put a piece of tape on the middle of the hub shell, set my calipers at half the OLN measurement (in your case 67.5mm) and mark that on the tape. Then measure from that mark to the center of each flange.

    Pretend this is a rear hub. Measure from the end of the axle 67.5mm. That's 'center'.



    Make sure you measure from the end of the axle.



    Center of the flange to the center of the hub.

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  6. #6
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    Thanks cxwrench! I'm all good to go now, spokes ordered. Interestingly, if I adjusted the center to flange distances by 1-2mm each direction, the spoke lengths were essentially the same, just moved .2 mm or so.

    Now awaiting the parts to begin the build!

  7. #7
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    Quote Originally Posted by zucchiniboy View Post
    Thanks cxwrench! I'm all good to go now, spokes ordered. Interestingly, if I adjusted the center to flange distances by 1-2mm each direction, the spoke lengths were essentially the same, just moved .2 mm or so.

    Now awaiting the parts to begin the build!
    If you haven't already, buy Roger Musson's e-book on wheel building. It's $12 with lifetime updates. Probably the best $12 you will ever spend. Follow it to the letter and you will be almost guaranteed success.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  8. #8
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    Quote Originally Posted by Lombard View Post
    If you haven't already, buy Roger Musson's e-book on wheel building. It's $12 with lifetime updates. Probably the best $12 you will ever spend. Follow it to the letter and you will be almost guaranteed success.
    Thanks, yep, I've got that book and it got me through my first build a few years back!

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