setup on the TT geometry

Discussion in 'Cycling Equipment' started by andyanansu, Apr 2, 2005.

  1. andyanansu

    andyanansu New Member

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    Hi
    I'm just building my first Time Trial/Triathlon Bike (I will use for both)
    some thing I want to make sure about the setup:

    1:
    Because the seat tube angle is more steeper than the normal road bike,
    as a result, it 'push' the rider more to the front,
    do you still adjust your saddle so that your knee is just above the pedal?
    or should your knee in front of the pedal? if so, how much?

    2:
    When I'm on my Tri Bar position, what sort of angle (to horozontal) should my arms be? (my arms between my shoulders & elbows)

    Thanks for any helps
    Andy
     
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  2. biker7

    biker7 New Member

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    Ans. 1. : The whole concept of a Tri bike is a slack tube frame that automatically places the knee forward of the pedal axis to provide (in theory) more power. The downside aside from higher knee flexion is as you say your weight now tends to fall more forward which is less comfortable to the recreational cyclist but that isn't the objective with a Tri bike as you want your body weight to load the pedals. Keep in mind when you ultimately power the pedals you will thrust yourself out of the seat which proves the point. As to how much, that is rider specific. A revisionist or contrarian view point is that of a recumbent bike which applies pedal force at a 45 degree angle or so to vertical in the opposite direction. In the case of a recumbent the seat has a back rest which acts as a reaction surface that allows the rider to provide pedaling force. In the case of a conventional bike it is the force of gravity or the vector of gravity based upon where a rider sits relative to the pedal axis that determines level of pedaling efficiency. As with a recreational cyclist there is no idealized position so you will have to determine what works for you. As to how forward you position yourself is largely based upon your pedaling intensity. If you reduce your effort you will be most uncomfortable as you will be falling forward and putting undue stress on your hands and upper body.

    Ans. 2: As with KOPS...there is no idealized back angle for all riders...it is rider specific based upon body proportions, preference and flexibility.

    HTH,
    George


     
  3. andyanansu

    andyanansu New Member

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    Hi

    Thanks for the detailed Answer in question 1,

    The question 2 is about my arms angle, not back angle.
    e.g. how far should I set my tribar in front of me
    so what sort of angle should my arms be compare to verticle?
    This will be very important for me to handle the steering safely & correctly.

    Thanks
    Andy
     
  4. biker7

    biker7 New Member

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    Arm angle is related to back angle which is a function of not only your proportions relative to frame size including top tube length but your muscularity/flexibility. I couldn't even begin to speculate a target or range. Geometry is specific to each one of us. What I suggest is before you purchase or build a frame is to call around and ask for the most knowledgeable TT bike man in your area for a fitting. Your bike will end up being a compromise if you use it for anything more than pure speed because comfort and speed are generally on oppose poles.
    Best of Luck,
    George
     
  5. blacktoe

    blacktoe New Member

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    There is a good article on "slowtwitch" (Tech Center) web page about tri bike setup that may answer some of your questions. I am a beginner so my knowledge is limited.

    According to this article a 90 degree angle or as close to it as possible is what to shoot for with the chest - upper arm angle. A 90 degree angle is also preferred between the chest and leg (position defined in the article). This article pretty much says if you can maintain these angles you can do what you like with the rest of the setup.

    I hope this helps,
    Randy
     
  6. andyanansu

    andyanansu New Member

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    George:

    I think the back & arm angle shouldn't be affecting each other
    because you can bend as low as to horozontal as possible
    and you can still can set the tri bar as front or back as possible
    this could be done by different top tube/ stem (adjustable)/ tribar combinations

    What I'm not sure here is how front/back should the tribar set to so it's theoretically the best for TT

    But thanks for your helps

    Andy
     
  7. andyanansu

    andyanansu New Member

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    Hi Randy
    Have you got a link for that article? I can't find it.
    Thanks for your helps
    Andy
     
  8. blacktoe

    blacktoe New Member

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  9. andyanansu

    andyanansu New Member

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