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Thread: HTA changes.

  1. #1
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    HTA changes.

    If I didn't show up lit to math in high school I may be able to figure this out. I posted here because I need a frame builders math.
    I have a HT with a 100mm fork with a 70.25 HTA. If understand correctly and install a 120mm fork that will slacken he HTA by 1degree. Would this be static or after the 5-7 mm extra sag?
    So the head tube would end up rising 20mm static. If I put a 1 degree head set to slacken it then how much would that lower the head tube?
    Would the head tube be close to original height? Static or after sag?
    I have seen posts about angle headsets but no one seems to mention how this drops the front down.
    Am I making sense?

  2. #2
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  3. #3
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    I did say I spent high school math lit up didn't I?

  4. #4
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    You got measuring tools?

    Right Triangle Calculator and Solver

    Maybe calculator 4 would work for you, if you have the A2C lengths of each fork, and you can confirm your confusion regarding static vs sag by measuring your current setup.

  5. #5
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    Try this tool to compare changes:

    https://bikegeo.muha.cc/

  6. #6
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    Quote Originally Posted by rlee View Post
    If I didn't show up lit to math in high school I may be able to figure this out. I posted here because I need a frame builders math.
    ...
    Am I making sense?
    To answer your last question: sorta, but not really.

    What's you're underlying concern? That the bars be at exactly the same height? It's unclear to me if the point of the angleset is for it's own sake (i.e. you really want to slacker the bike even more) or if you are just trying to lower the bars back to their original height.

    (Side note: I'm not sure what bike that has a >70 HA also has a headtube sized to take an angleset, but I guess it's plausible)

    You seem to have a reasonably good grasp of the numbers themselves and what does what given that you (self-described) don't understand any of the math behind it. Rather than go through the calculations, maybe it'd be helpful for you to take one more step away from the numbers to get at what your concern really is.
    I make bikes. www.feldybikes.com

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