Motorcycle Forum / General / Sportbikes / June 2005

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Thanks or excellent appraisal

Thats because those guys are pushing the edge.. way out of
whack for the normal rider to develop and accomodate to ....
especially when riding on the street...the racers are
demonstrating an extreme.

Andy is demonstrating whats useful on the back roads where one
is not counting on even traction  and is not pushing the G
forces to the same limit....leaning off at those extremes on
the street would force turn speeds needed to keep the bike up
way too high.

Lately Ive been leaning my upper body, shoulders and head into
the turn so my chest is over the outside bar and Im looking
past the side of my tall somewhat narrow wind screen.. that
presses the outside knee into the tank naturally.. seems to
provide a lot more stabiltiy and instill confidence, and the
bike is not laid over near as far in relation to corner
speed...I'd say corner speed is up30% or more as compared to
straight up riding.

With clip ons, from the rear it would look typical to Andy's
race course picture...not that good of form no doubt ...but
along those lines.

With the higher wider bars I have no idea how it looks.. but
it feels  real good to say the least.  Even at the edge of the
front tire it feels better.  I think it might something
related to the center of gravity being inboard of the axis of
lateral rotation.    In other words the CG is *inboard of that
axis so ones body wt has leverage against centrifical forces.

As speeds pick up I tend to get the upper body lower but with
higher bars thats limited.. thus for haul a.s riders the
necessity for clip ons.

With the CG in the center of the rotating mass, as with
Colemans pic, the net CG  it has no leverage against
centifical force on the center of lateral rotation forced by
the bikes contact with the road.

With the CG say outside the center the rotating mass, as if
keeping the body upright in a turn, the CG has leverage in
favor of centrifical forces tending to high side the bike.

Thats why you see the world class flat trackers leaning way
in, with the body mass low..  the more of that you do, the
farther inboard of the bikes natural CG is the net actual
center of gravity rider included.

Why is it then that the dirt track riders lean in but DO NOT
hang off and also keep the bikes much closer to upright than
road racers.

Thats because on the dirt... traction is a killer issue. and
so the bike needs to be kept largely upright on the tire
patches for maximum traction/

centrifical forces are countered by crossing the bike up and
having rear wheel traction drive the front end of the bike
into the turn against these forces.

So the rider leans in, but the bike stays closer to vertical.
On short tracks the bike is very often entirely verticle in
the turns.  It doesnt high side only because the rear wheel is
spinning and there is not enough traction to keep the back
from drifting out...so its a balance... maintained by the
rider/ bike body mass inboard of the bikes CG.

On the street, with unpredicatable traction a mix of the two
works best apparently.

For demo's one would look at motard racing pics.

Phil Scott

Phil Scott