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  1. #1
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    QR hub on a (similar width) TA frame

    Hello -

    this a more general version of my TA-197 question i posted in Fat bikes (My problem would be solved if what i need was _made_ in TA-197; it's not at least at this time, so I can't take the standard advice of just buying new hubs (or a hub-motor in my case).

    I am not understanding the typical answer that it's impossible to run a quick-release hub in a through axle (or bolt) frame with adapters.

    My understanding is that a QR system's only purpose is to clamp the frame to the lockut; once that pressure is there clamping the two together, all stress is carried by friction and compression.
    • More specifically the load goes: hub-body races --> bearings --> race/axle assembly --> interface from the race/locknut to frame. The forces on the axle are only interior to the hub system, keeping the races from separating under the axial component of the load from the balls.. The axie gets no meaningful radial support from the dropouts. Radial load is carried by friction of the locknut/frame.
    • This differs from a TA afaict in that the TA itself carries the load from the bearings/races and then the axle is supported radially by the frame.


    So, at least in the case where O.L.D. / overall width is similar, why can't i have an adapter that lets me clamp the QR hub's locknuts to the frame? All the adapter would need to do is locate the QR axle in the center of the TA hole at the appropriate offset for the disc brakes.

    Thanks!!

  2. #2
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    BTW, my Through axle system is actually more like a through bolt, and the dropouts are actual dropouts, not holes, so it's a little odd. But possibly relevant to the answers, and it means that my frame is already acting like a QR system where loads are served by the friction of the interface, not radial support of the axle/TA-hole. Frame is steel.QR hub on a (similar width) TA frame-surly_big_fat_dummy_dropout_detail.jpg

  3. #3
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    Quote Originally Posted by high_desert_mud View Post
    My understanding is that a QR system's only purpose is to clamp the frame to the lockut; once that pressure is there clamping the two together, all stress is carried by friction and compression.
    • ... The axie gets no meaningful radial support from the dropouts. Radial load is carried by friction of the locknut/frame.

    That is incorrect. In a QR system the vertical load is transferred from the frame to the axle & visa versa via the shoulder on the end caps. This shoulder rests against the top of the dropout. If you do not fully insert the wheel to allow the shoulder to bear the load you will most often get creaking and popping sounds as the QR nut slips on the frame.



    Friction does act to hold the wheel in place as the frame is lifted, thereby unweighting the wheel.

  4. #4
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    Quote Originally Posted by BlueCheesehead View Post
    That is incorrect. In a QR system the vertical load is transferred from the frame to the axle & visa versa via the shoulder on the end caps
    A good point, and sounds correct, thanks.

    Regarding the question, though - this doesn't seem to preclude using an adapter to fit the 9 or 10mm QR axle into a slot for a 12mm through axle ... the vertical load function is going to be just as functional. The pressure on the frame for the same load should be reduced, actually. as the area increases with diameter.

    So a good correction regardless; but do you think this affects viability of spacers in my application?

  5. #5
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    On another thread someone found these.
    https://surlybikes.com/parts/small_p...dapter_washers

    so it looks like Surly is saying using and adapter is just fine. I wonder why the old threads say it's a no-go?

    Name:  surly adapter washers.jpg
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  6. #6
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    Yes, you can make adapters to work.

    A thru axle hub, thru bolt hub and quick release hub do pretty much the same thing. The hub resists flexing by the axle inside the hub in both cases. The thru axle squeezes the hub in position and so does the QR. So a thru axle is not necessary. The thru-bolt does support the hub in place of the QR end cap nubs, but if the hub has a weak axle inside of it, it can still break, and I have seen hub axles broken in the middle even when a thru bolt was used.

    It looks like you have a standard frame. The nubs at the end of Quick release style hub end caps are designed to fit into the dropouts shown in your image. A thru bolt of the correct size can also fit into these dropouts. The DT SWiss RWS thru-bolt system for 9mm front and 10mm rear drop outs removes the nubs from the hub end caps and replaces them with a 9mm thru bolt front and 10mm thru bolt rear.

    For reference the benefit of the thru-bolt is that it doesn't stretch as much as a QR so the hub should twist less in the drop outs.

    The additional benefit of a true thru-axle frame is that it should allow the hub to fit more consistently in the frame or fork because it has threads to guide one side and a hole on the other (instead of a slot).

    Since you may be trying to bridge a long span to fit your motor into a 197mm width you will need something very strong to support the hub and the cantilever distance outside of the hub. A solid steel thru bolt with spacers on each side may work, but if there is more than a few mm of cantilever it will probably bend.

  7. #7
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    Quote Originally Posted by changingleaf View Post
    ...
    It looks like you have a standard frame. The nubs at the end of Quick release style hub end caps are designed to fit into the dropouts shown in your image.
    It looks standard, but it is not. The Surly Big Fat Dummy utilizes a unique "Thru Axle Dropout", or in plain terms a 12mm slot that a thru axle can fit into. Standard QR end caps will not fit that tightly. The Surly adapters shown above should extend the axle length from 190 to 197 and increase the diameter of the shoulder to fit the larger BFD slot. Again, I would call Surly to confirm. He would then be relying on a quick release to hold all in place.

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