USD Conversion (Bearing Cup Method)

  • USD Coversion (Bearing Cup Method)

    I've been asked on many occasions on how I managed to fit Upside Down Forks to my DTRE.

    I remember thinking foolishly about it back when I bought the forks. I bought a set of miss match components before quickly realising I am going to need to need the match together components.

    So before you go ahead a buy anything, I'd suggest having a quick skim through this to familiarise yourself with what is necessary.

    I shouldn't bother about what bike to obtain your forks from. There is no simple method to this conversion, they all require some amount of work to get it right. Whether it's modifications to the frame or the wheels. You will want to spend time getting it right.

    The key thing to do is ensure you get both the Triple Clamps and the Fork Stanchions. It will be helpful if you obtain the front spindle and nut whilst you're here.

    Obtain Like Items

    • Triple Clamps
    • Fork Stanchions
    • Spindle & Nut

    From here you should be able to fabricate the rest.

    What are you going need then?

    You may be lucky, you might find your forks just fit and away you go. But somehow I do doubt it.

    You are going to be scrapping the DTR Forks and Triple clamps. You are going to notice that the stem on the DT is considerably smaller than your USD's. It's this component that presents a problem.

    The stem is going to be shorter and thinner. And this means the bearings used on the DT won't fit the USD's.

    That's fine, they are crappy push bike bearings anyway. We want to derive a system that utilises taper roller bearings.

    This conversion is going to raise the height of the handle bars, as well as uprate the whole suspension system.

    If you look at the head stock on the DT. You will notice that the tube is a consistent size throughout ( except the two tapers that houses the bearings. In this sense, so long as the stem you are using fits through this hole (I'd be surprised if it didn't) then you're good to go.

    The bottom bearing on my DT was the same as the bottom bearing on my forks. Taper roller bearing already. And for me this was a straight swap, well not exactly, I needed to space the bottom bearing out but it was relatively simple process.

    If you find that it doesn't fit, then you will need a bearing cup to fit both the bottom and top of the head stock. I am going to describe the process I went through for the top of my headstock, but repeat the process for the bottom, ensuring that your measurements for the stem take into account you are going to space the lower and top components.

    Let's examine a 2D representation of the DT Headstock.


    Imagine that's the tube that the stem runs through. Your triple clamps are fixed to this. Bearings sit inside the frame to allow you to rotate the wheels.

    What you want to do is to create an extension to this frame to enable you to run bearings suitably big enough for your stem.

    The bearings you are going to fit only need to be big enough in the internal diameter. I once had someone tell me this method wouldn't work for them due to the lack of availability of bearings for their forks. Which is rubbish. You design the size of the cup to take whatever bearing you want to fit. In otherwords, so long as it fits on the stem, the width and depth can be whatever your cup designs account for.

    Eventually you will design a cup to sit inside the frame (Where the old bearing went) ensuring you remove the race before hand.


    In this picture, notice how the internal diameter of the frame has been enlarged to allow the new bearing to sit inside here. The red will fill the space of the old headstock housing. Your triple clamps should now be at the right height, with enough space for the bearing to sit inside. It should be able to rotate freely.

    Here was my exact dimensions for 2001 WR450 Forks.

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    Here is the product you will aim to make.

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    With the new race for your bearing installed.

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    With the bearing installed

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    How it compares contrast to the existing frame.

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    Get it painted to match your bikes theme and enjoy fabulous suspension!

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    Don't forget, new brackets will be necessary for your clocks.

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    Hopefully this is helpful!