Mountain Bikes · Public discussion

Need stretch: stem or seat post?

Started by Raptor · · Last activity · 24 posts · 1,013 views

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Mountain Bikes
Published
7 July 2006
Last activity
10 July 2006
Original author
Raptor
Posts
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  1. Raptor said:
    CowPunk said:
    Mark Hickey said:

    The key is to always (always, always) start with a bike that fits.
    Trying to force fit the wrong bike means you'll spend all your riding
    time having less fun than you should.

    Mark's right.
    A frame has a top tube length designed to obtain a certain
    center-of-gravity.
    When you go adjusting a saddle way back with a bent seat post you screw
    that center-of-gravity up.

    That's kind of silly when you realize that people are different. I have
    several pounds of weight above my waist that many mountain bikers don't.
    By bending or straightening my arms, I can move my COG instantly, on
    most any bike.

    You could say the same about pretty much any size bike for any size
    rider - they could "force" a good balance going into a corner - but
    most of us are happiest when the bike is balanced optimally when we're
    JRA (Just Riding Along).

    Quoted message said:

    Most high performance bikes are bought "small," the smallest frame that
    fits. My bike's seat tube is long enough. The top tube might actually be
    optimal for a different rider with my particular build. I've just become
    comfortable leaning forward with arms more outstretched than many riders.

    Proper fit affects a lot of aspects of the bike - biomechanical
    efficiency, handling, comfort, etc... we all search for the best
    compromise between all of those, and your search has resulted in a
    position that most of us would find somewhat uncomfortable and
    inefficient, and that almost certainly results in handling quirks that
    someone riding the same bike in a "normal position" wouldn't
    experience. But if it works for you, go for it.

    Quoted message said:
    Quoted message said:

    If you can't get your saddle back far enough with a regular post then
    you need
    to go and buy a larger frame with a longer top tube.

    Seat tube angle and length has more to do with "proper" saddle location
    than top tube length.

    All seat tube angle does is sets the fore/aft range of the saddle. As
    long as the combination of the frame's seat tube angle and the seat
    post's offset allow you to put the saddle in the correct position
    relative to the crank, the rear half of the bike "fits". Much more
    important is the ability to get the "cockpit length" right without
    having to resort to a too-short or too-long stem.

    Mark Hickey
    Habanero Cycles
    http://www.habcycles.com
    Home of the $795 ti frame

  2. Duncan said:

    "CowPunk" <[email hidden]> wrote in message
    news:[email hidden]...

    Quoted message said:


    Quoted message said:

    "Duncan" <[email hidden]> wrote:

    Quoted message said:

    >Even off the seat I have a tendancy to weight the back wheel:


    http://www.ftf.com.au/racegalleries/Statechampsgal2/images/CIMG0640_JPG.jpg

    Are you sure that's a 19" frame?

    It looks too small for you.

    Yeah it's definatly a 19", brands vary a lot in shape and where they
    measure. Keep in mind the bike is a race bike where agility is quite
    important. Our local race courses have a tendency to by quite tight
    singletrack where quick steering pays off.

    The difference in wheelbase between a 17" and 19" or 21" frame is
    pretty minimal in terms of the effect on handling the twisty stuff.
    Much more important is the balance on the bike. All I can say is that
    I know I'd have to slow down in twisty singletrack if I were to
    unweight the front wheel even half as much as you do in that photo.

    Mark Hickey
    Habanero Cycles
    http://www.habcycles.com
    Home of the $795 ti frame

  3. CowPunk said:
    Raptor said:

    Seat tube angle and length has more to do with "proper" saddle location
    than top tube length.

    So, with your rear saddle position, can you drift both wheels in a
    corner,
    or does one break loose before the other?

    I bet your rear slides out first?

    I don't think I can drift both wheels in a corner in any saddle
    position. 🙂 If I want the front to slide out first, I put more weight
    over it. Or less, depending on the traction.

    --
    Lynn Wallace http://www.xmission.com/~lawall
    I have nothing but contempt and anger for those who betray the
    trust by exposing the name of our sources. They are, in my view,
    the most insidious of traitors."
    George H.W. Bush, April 16, 1999,

  4. "Mark Hickey" <[email hidden]> wrote in message
    news:[email hidden]...

    Quoted message said:
    Duncan said:

    "CowPunk" <[email hidden]> wrote in message
    news:[email hidden]...

    Quoted message said:


    > "Duncan" <[email hidden]> wrote:

    > >Even off the seat I have a tendancy to weight the back wheel:
    >

    Quoted message said:

    http://www.ftf.com.au/racegalleries/Statechampsgal2/images/CIMG0640_JPG.jp


    g

    Quoted message said:
    Quoted message said:
    Quoted message said:


    Are you sure that's a 19" frame?

    It looks too small for you.

    Yeah it's definatly a 19", brands vary a lot in shape and where they
    measure. Keep in mind the bike is a race bike where agility is quite
    important. Our local race courses have a tendency to by quite tight
    singletrack where quick steering pays off.

    The difference in wheelbase between a 17" and 19" or 21" frame is
    pretty minimal in terms of the effect on handling the twisty stuff.
    Much more important is the balance on the bike. All I can say is that
    I know I'd have to slow down in twisty singletrack if I were to
    unweight the front wheel even half as much as you do in that photo.

    That photo was more to show the general geometry of my setup. The actual
    pose is in anticipation of some heavy breaking back into the single track.
    It would get very uncomfortable riding around like that everywhere.

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