T-man,
Well I'm not sure that what those photos are indicating is in the area of classic 'countersteer' in the motorcycling world. What we're seeing is perhaps closer to the countersteer we all experience when driving a car on ice.
'Countersteer', as the motorcycle books call it, is a suble flip of the front wheel that results in quickly throwing the center of gravity slightly askew of the tire contact patches, ahead of and slightly to the inside of an approaching curve, so that the process of leaning can begin. It's a subtle and almost instanteous tweek, and is probably learned instinctively on those first few shakey rides on a bicycle.
When running and walking we do the same thing. Without a shift in the center of gravity in relation to the center of support, there ain't no turn going to happen.
What the photographs are illustrating is a loaded chassis during hard cornering, which is perhaps different than 'countersteer'.
In a hard cornering scenario, both tires are fully loaded in a lateral direction with the rear tire also bearing an additional thrust force forwards. There isn't a lot steering going on with the front tire since the front tire is siding sideways as it turns (pushing), and the rear tire is sliding sideways and rearward as it turns (drifting).
Riding in that posture is like surfing sideways across the front of a wave. One throws the bike into the curve and then one surfs around the curve without a lot of control. Steering is done by subtly altering the front wheel push with the inside hand, while altering the rear wheel drift with the throttle and body load on the seat and the pegs.
Flat track riding illustrates all of the above in extreme. The same things are happening on a bike when rounding a curve on asphalt as are happening when sliding sideways around a curve on a flat track. Only because of the higher friction of the asphalt, everything is subtler.
Watch Rossi in slow motion while cornering. He is constantly shifting his body position in a curve. that's how he's steering. Just like the flat trackers.
Now . . . add to all the above the geometrical fact that when the projection of axles strike the ground at a location inside of the curve radius point, the bike wants to turn-in sharper than the radius of the curve. Picture a rolling cone, where the point of the cone is the spot where the axle projection strikes the ground and the base of the cone is the wheel. That cone wants to turn-in when it's rolling using the point as the radius point. Something has to counter that inward force on the wheels.
I think the straight-ahead or slightly outward direction of the front tire in the photographs is the result of surfing the combination of tire slide, plus any small steering inputs, plus countering the tendancy of the tire to want to turn-in sharper than the curve radius.
That's the beauty of track tires. They provide a lot of leeway in the safe envelope of surfing and they are very, very sticky. A wide envelope lets a rider feel when a slide is easing out of control towards a tire release. Street tires (because they are much harder) have a much narrower surf envelope and very few riders can feel the edges of that envelope before the tire lets go.
All of this is just my opinion, though it's based on experience and observation.
WTF do I know.
C
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Another sunrise, These bright and crystal moments, Crow flies overhead.
Terrytori said:
