Re: Countersteering

"Timberwoof" <timberwoof.spam@xxxxxxxxxxxxxxx> wrote in message news:timberwoof.spam-17EB8A.08441117092007@xxxxxxxxxxxxxxxxxxxxxxxxxxx
> Yeah, but the torque is expressed on the tire by turning the tire in
> relation to is direction of travel. It doesn't take much sideways force
> to get the bike to tip over, so the motion is pretty slight.

Very slight indeed. So much so that it takes bugger all to see it.
But on tighter turns (say radii under 100 feet), the front wheel seems
to be tangent to the turn. The rear wheel is turning inside (remember
the front wheel out-riding?). So the steering head is pointed into
the turn by just a tiny but sometimes visible bit.

You're saying that motorcycles oversteer.

Actually, that's understeer. If it were completely neutral, the steering angle at steadystate is 0. Deviation from 0 indicates over- or understeer. Steering into the turn at steadystate indicates understeer. The front requires a greater slip angle than the rears to maintain the same instantaneous turn rate.

We saw before that steering geometry and camber thrust dominates up to some lean angle. For the one tire that we saw published data, that angle was about 22 degrees of lean. Slip angle was zero or even slightly negative in this performance region. The important point is that geometry dominates in most turns in street riding. A naive planview diagram of a bike in a turn is thus sufficient for understanding front wheel outriding. Both wheels are tangent to their respective arcs of motion. The planview instantaneous center of turn is the intersection of their projected axes. The radius travelled by the front, steerable, wheel is larger than that travelled by the rear. This fully explains outriding, I think, without resorting to talking of slip angles. (Over- and understeer relate to slip angles.)

One decidedly simple way to magnify the motion of the steering head for measurement is to rigidly mount a long pointer to the steered wheel. That is, duct tape, clamp, or weld a spear (or broomstick) to the front fender, parallel to it's plane of rotation. Its motion should be unambiguous and obvious when videotaped from the rider's point of view.


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Relevant Pages

  • Re: Countersteering
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    (rec.motorcycles)
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    (rec.motorcycles)
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