Knee pain from one bike, but not the other

Discussion in 'Road Cycling' started by Benjamin Slade, Sep 1, 2005.

  1. I have two bikes, one is a high end road bike (Airbourne - Valkyrie),
    the other is a cheap bang around mountain bike (Gary Fisher - Tarpon)
    that I use for around town stuff.

    On the road bike, my knee is fine. On the mountain bike, my right knee
    hurts. I'm trying to figure out what the difference is. I see two..

    The mountain bike has a lower seat angle. Ie. the seat post is more
    tilted back, effectively moving the seat farther behind the pedals.

    Also, the mountain bike has 3 gears on the front ring. This combined
    with the geometry of the pedal crank arms means that the pedals are
    farther apart (farther left and right).

    With regards to the seat post being tilted back, I've always felt like
    this causes the rider to put more pressure on the knee higher in the
    stroke. Exactly where my knee has problems.

    I'm debating selling the cheap mountain bike, and trying to find a
    hybrid bike that's closer to the geometry of my road bike (pedals closer
    together, seat post less tilted back so the seat is more over the pedals).

    Any experiences to share or opinions on the subject?

    Thanks
    Ben Slade
    Washington DC
    (if sending me email, append 030516 to the subj to bypass my spam filters)
     
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  2. rdclark

    rdclark Guest

    Benjamin Slade wrote:

    > Any experiences to share or opinions on the subject?


    As you've discovered, saddle position relative to the pedal spindles
    can be critical. You should start by quantifying the differences to see
    if they're significant.

    Sitting on the bike with your butt where it usually is, put one crank
    exactly parallel with the ground, forward.

    Drop a plumb line (a weight on a string) from the kneecap on that side,
    from the spot just under the pointy protrusion on the kneecap, and see
    where the weight falls relative to the pedal spindle.

    Do this for each bike. Then see if you can adjust the position of the
    MTB saddle so that it yields the same relationship between knee and
    pedal spindle that you have on the Airborne. You'll have to adjust
    height as well as fore-and-aft position, and you want the same amount
    of knee extension on both bikes, as well as the same knee/pedal spindle
    relationship.

    As for q-factor - the distance between the pedals - the obvious step is
    to measure the bikes and see if there really is a difference. If there
    is, the amount and direction you need to change the MTB will determine
    your strategy. Save that for later, when you know what's required.

    RichC
     
  3. Bill H.

    Bill H. Guest

    Just a thought, but could it be that you're pushing too high of a gear
    on the mountain bike and spinning a lower gear on the road bike?
     
  4. John_Kane

    John_Kane Guest

    Benjamin Slade wrote:
    > I have two bikes, one is a high end road bike (Airbourne - Valkyrie),
    > the other is a cheap bang around mountain bike (Gary Fisher - Tarpon)
    > that I use for around town stuff.
    >
    > On the road bike, my knee is fine. On the mountain bike, my right knee
    > hurts. I'm trying to figure out what the difference is. I see two..
    >
    > The mountain bike has a lower seat angle. Ie. the seat post is more
    > tilted back, effectively moving the seat farther behind the pedals.
    >
    > Also, the mountain bike has 3 gears on the front ring. This combined
    > with the geometry of the pedal crank arms means that the pedals are
    > farther apart (farther left and right).
    >
    > With regards to the seat post being tilted back, I've always felt like
    > this causes the rider to put more pressure on the knee higher in the
    > stroke. Exactly where my knee has problems.
    >
    > I'm debating selling the cheap mountain bike, and trying to find a
    > hybrid bike that's closer to the geometry of my road bike (pedals closer
    > together, seat post less tilted back so the seat is more over the pedals).
    >
    > Any experiences to share or opinions on the subject?
    >
    > Thanks
    > Ben Slade
    > Washington DC
    > (if sending me email, append 030516 to the subj to bypass my spam filters)


    If you're using clips or clipless pedals make sure the ??? what is that
    term?? anyway make sure your toes are pointing at the same angle. Also
    check things like saddle height etc. You may need to play around with
    them a bit or get a couple of opinions from the local bike club or
    LBSs.
    John Kane
    Kingston ON
     
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