Jerald Powell
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Folks.
In addition to all that's been said: lifting your lead but off the
saddle, probably more significantly transfers your weight to the bottom
bracket rather than the top of the seat tube... Also, there are a
number of riders, some pros even, that for reasons really obscure to me
insist on sticking their tails up in the air and putting their weight
on the handle bars. This may work OK under some limited conditions...
but generally it exacerbates any tendency to fork wobble, unweights the
back tire allowing it to bounce around, squishes the front tire
increasing road resistance, and puts the rider in a really awkward
position to corner, absorb bumps or holes, or maneuver out of harms
way.
Seems to me that rider position has a great to do with how comfortably
and how safely the rider descends. When coaching new racers, my
recommendations are generally to keep your weight over the bottom
bracket, keep your hands light on the bars and either up in the bend
(elbows way bent) or hands on top, elbows tucked in. Pedals should be
generally keep moving or for short periods rest in a horizontal
position so that the bike is evenly weighted laterally... outside pedal
down and weighted cornering of course.
Finally, It's pretty clear that spoke tension is often culprit in an
unstable bike... and that many riders fail to go over their wheels
anywhere frequently enough. If you're going to race, learn how to
maintain your wheels and check them before every start.
On Jul 14, 2004, at 9:38 AM, Peter LaPorte wrote:
"Finally, let us talk a little about death wobble, or high-speed
wobble, or high-speed shimmy. This tends to happen on larger frames
and with larger riders, and is NOT caused by bad or loose headsets or
misaligned frames. As one Rec.Bicycles.Tech regular well described it,
'Wobble is a harmonic effect and the resonant frequency of the
bike/rider combination is what determines when a frame will wobble.'
(Brian Nystrom). The best way to get your bike to cease its wobble is
to place your thighs against the top tube, and to unseat yourself from
the saddle. Nystrom continues: 'Anything that affects the resonant
frequency of the system (tire pressure, spoke tension, fork stiffness)
will affect wobble. Raising your weight off the saddle decouples your
body from the frame at the saddle and often stops wobble cold.'
Therefore, as a long-term solution, changing your wheels or tires may
help, or you might simply have your bike shop re-tension your spokes."
Jerald M Powell, AICP
Community Planning
1926 SW Madison Street
Portland, OR 97205
503 222 7173
503 799 7823
jpow-@spiritone.com
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Folks.
In addition to all that's been said: lifting your lead but off the
saddle, probably more significantly transfers your weight to the
bottom bracket rather than the top of the seat tube... Also, there
are a number of riders, some pros even, that for reasons really
obscure to me insist on sticking their tails up in the air and putting
their weight on the handle bars. This may work OK under some limited
conditions... but generally it exacerbates any tendency to fork
wobble, unweights the back tire allowing it to bounce around, squishes
the front tire increasing road resistance, and puts the rider in a
really awkward position to corner, absorb bumps or holes, or maneuver
out of harms way.
Seems to me that rider position has a great to do with how comfortably
and how safely the rider descends. When coaching new racers, my
recommendations are generally to keep your weight over the bottom
bracket, keep your hands light on the bars and either up in the bend
(elbows way bent) or hands on top, elbows tucked in. Pedals should be
generally keep moving or for short periods rest in a horizontal
position so that the bike is evenly weighted laterally... outside
pedal down and weighted cornering of course.
Finally, It's pretty clear that spoke tension is often culprit in an
unstable bike... and that many riders fail to go over their wheels
anywhere frequently enough. If you're going to race, learn how to
maintain your wheels and check them before every start.
On Jul 14, 2004, at 9:38 AM, Peter LaPorte wrote:
<excerpt>
"Finally, let us talk a little about death wobble, or high-speed
wobble, or high-speed shimmy. This tends to happen on larger frames
and with larger riders, and is NOT caused by bad or loose headsets or
misaligned frames. As one Rec.Bicycles.Tech regular well described it,
'Wobble is a harmonic effect and the resonant frequency of the
bike/rider combination is what determines when a frame will wobble.'
(Brian Nystrom). The best way to get your bike to cease its wobble is
to place your thighs against the top tube, and to unseat yourself from
the saddle. Nystrom continues: 'Anything that affects the resonant
frequency of the system (tire pressure, spoke tension, fork stiffness)
will affect wobble. Raising your weight off the saddle decouples your
body from the frame at the saddle and often stops wobble cold.'
Therefore, as a long-term solution, changing your wheels or tires may
help, or you might simply have your bike shop re-tension your spokes."
</excerpt>Jerald M Powell, AICP
<italic><x-tad-smaller>Community Planning</x-tad-smaller></italic>
1926 SW Madison Street
Portland, OR 97205
503 222 7173
503 799 7823
jpow-@spiritone.com
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