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  1. #1
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    Understanding frame geometry

    Hey all, I'm looking to purchase a bike, but I want to understand the relationship on the geometry of frames. I'm posting in Frame Building instead of General b/c I'm trying to weed out the answers from people who habe a general understanding.

    I'm 5'7" and currectly ride a Giant Talon. I want something s little more playful, but I really do enjoy this bike over my previous full squish 26. I'm thinking about a 650b, steel, but haven't ruled out a Niner as a shop (who had no 650b alternative) told me I should look at a Niner. Not totally sure I would need a steel frame 29, but a sir 9 is on the list.

    Anyway, I was looking for something that turned a little better, but talon has the shortest wheelbase. It seems counterintuitive that a longer wheel base bike would turn better, but that is why this padowon is seaking the expertise of you jedi masters (Sorry for the Starwars ref).

  2. #2
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    Your question is way, way too general. You can spend a lifetime understanding (or not) frame geometry and how it interacts with rider fit/preference.

    If you try to ask some specific questions, you may get some decent answers but the first step might be to simply get the geometry numbers for your current bike, plus the bikes you're interested in riding, do a lot of reading, and then demo/borrow/rent some bikes to compare.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  3. #3
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    Sorry, had to leave to take my daughter to practice. I ride moto, but not looking for Downhill. More xc w/ flow. Current ride is a Giant Talon. I have a spread sheet w/ specs., but I'm l'm looking at a sir 9, Kona explosif, soma b side, and possibly Jamis Dragon.

    model size H/A S/A T/T H/T C/S W/Base Standover B/B Height
    Giant Talon Small-16 70.5 73 22.5 4.3 17.6 41.9 28.4


    Niner Sir 9 small 69.8 72.3 23.3 3.9 17.3 42.7 28.2
    w/ 100 mmtravel

    Kona Explosif 15 68 73 22.5 4.5 16.5 42.4 30 11.75

    Soma B Side 16.5 71 73 23.03/22.125 4.33 16.81 43.48 30
    Last edited by yzfrider; 05-28-2013 at 08:11 PM.

  4. #4
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    Quote Originally Posted by Walt View Post
    Your question is way, way too general...
    If you try to ask some specific questions......

    -Walt
    When I look at Stack, is there a relation to my leg length?

    When a manufacturer measures reach, is reach the same as as actual for top tube?

  5. #5
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    Stack: not directly related to leg length. Stack is the vertical dimension from the bottom bracket center to the top of the head tube. In general, most bigger frames have a larger stack, but some 29er models (for instance) use about the same head tube length/stack across all their sizes.

    Reach: is the counterpart to Stack. It's the horizontal direction measurement from the bottom bracket center to the top of the head tube. This kind of mirrors ETT, but ETT also takes into account the seat tube angle.

    Quote Originally Posted by yzfrider View Post
    When I look at Stack, is there a relation to my leg length?

    When a manufacturer measures reach, is reach the same as as actual for top tube?

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