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  1. #1
    Senior Member CHAS's Avatar
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    75 mm fork bend with 45mm trail?

    70mm rake with 45mm trail?
    Ordered a frame. Just got the option of having 70mm bend put into the fork. This will be with a 71.5 degree angle.
    That should equal 45mm trail or maybe more as the short frame has a greater angle than the taller ones.

    I want low trail. Is this too much?
    Pivot 5.7
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  2. #2
    Senior Member ftwelder's Avatar
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    Quote Originally Posted by CHAS View Post
    70mm rake with 45mm trail?
    Ordered a frame. Just got the option of having 70mm bend put into the fork. This will be with a 71.5 degree angle.
    That should equal 45mm trail or maybe more as the short frame has a greater angle than the taller ones.

    I want low trail. Is this too much?
    What is your wheel diameter? To calc trail posters need that info.

  3. #3
    Senior Member CHAS's Avatar
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    584 for 650B
    It should also take 622-700c wheels
    Pivot 5.7
    Rawland Drakkar 650B love it with 38mm Soma tires
    2009 Specialized Roubaix Ultegra
    Santana Fusion Tandem
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    Challenge Concept Trike
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    Homophobia is so gay.

  4. #4
    Senior Member Cassave's Avatar
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    Quote Originally Posted by CHAS View Post
    70mm rake with 45mm trail?
    Ordered a frame. Just got the option of having 70mm bend put into the fork. This will be with a 71.5 degree angle.
    That should equal 45mm trail or maybe more as the short frame has a greater angle than the taller ones.

    I want low trail. Is this too much?
    70mm rake at 71.5 degrees using a wheel radius of 340mm (700c) gives 40mm of trail.
    A 355mm radius would yield 45mm of trail.

    If you plan on carrying loads on the front that would make sense.

  5. #5
    tuz
    tuz is offline
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    homebuilt commuter, mixte, road and track (+ Ryffranck road)
    bla bla blog

  6. #6
    Randomhead
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    is the head tube angle slack to increase toe clip clearance? When you have a slack head tube angle, you need a lot of rake to get a low trail geometry

  7. #7
    Senior Member CHAS's Avatar
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    Thanks to all of you.
    Pivot 5.7
    Rawland Drakkar 650B love it with 38mm Soma tires
    2009 Specialized Roubaix Ultegra
    Santana Fusion Tandem
    2010 Specialized TriCross
    Challenge Concept Trike
    One knee scoped so far.

    Homophobia is so gay.

  8. #8
    Tell it as it is Silverbraze's Avatar
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    Quote Originally Posted by CHAS View Post
    70mm rake with 45mm trail?
    Ordered a frame. Just got the option of having 70mm bend put into the fork. This will be with a 71.5 degree angle.
    That should equal 45mm trail or maybe more as the short frame has a greater angle than the taller ones.

    I want low trail. Is this too much?
    the builder is giving you the option to decide your fork rake and trail?
    if so
    then this is the wrong approach
    the builder should have the nuts to know that they need to build for you
    for your desires and needs in the bespoke bicycle.
    what geo to fit under your position data
    To give the client options on geo is bad on the builders part atmco
    it's steel
    it's lugs
    let the others get on with the madness
    www.llewellynbikes.com
    www.framebuilders.org

  9. #9
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    I prefer a bit less trail for a road-going 650b with handlebar bag. If you're not using a bag, 45mm will feel pretty good, especially with medium-width tires. If you're using very wide tires it may be overly stable on the road.

    All of it is pretty unimportant, though. If you read enough (especially Bicycle Quarterly) it can come to seem as if a few mm of trail can be Earth-shaking. It isn't.

  10. #10
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    "To give the client options on geo is bad on the builders part atmco "

    I think you have a fair point there, but I would say there are exceptions. He may just be asking what kind of front end the bike should have in the same way the cogswell porteur had several, then the client has the options before them in the same way they would have options on an MTB vs a cross bike, except it is a little more narrow.

    For better or worse, we live in a world where the heart surgeon asks me what I want to do relative to various treatment options...

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