Understeer ... the good, the bad & the Technical

[Farnborough]

I'd answer O if I understand the phrase "Which car's yaw velocity increases most quickly?" Correctly.

I agree with you venkyhere, in that a chassis set for high speed has to have a "latent " understeer characteristic, if it's a high power rear wheel driven layout, to ultimately be cancelled out (the natural understeer balance) by application of torque.

One that has a knife edge response to steering becomes ultimately slower as you can't use much torque before it starts to rotate too far, that's from my experience in driving various different arrangements.

I would say that at the far reaches of pace in long corners, how much throttle you can apply is proportional to how much "understeer" exists through that period of operation.

There's clearly a different view on just how much understeer warrants that word in "layman" discussion on here.

[Greg Locock]

Yaw velocity is the rate at which the heading of the car changes. So in the very simple case, you apply 5 degrees of SWA to the left and hold it, and after some transient behaviour, the car steers to the left at a certain number of deg/s, which is its yaw velocity.

[Farnborough]

I'd still say the O car.

That is from my experience across different platforms, but could also see the answer as no difference if the example was not at the highest limit of adhesion for the tires given.

To place context of experience ... kart in dry or wet conditions, rally in tarmac (slick tire) or gravel, winter driving in Alps accent and decent with surface driven variables etc. Quite possibly my interaction is pollutant in pure technical response terms, primarily as I'm using descriptor in place of theory.

[Greg Locock]

Well I suppose I've had my fun. I'd have thought the way the question was set up made it obvious that I was expecting people to say O, when the answer is U. So, I guess we can kill this thread in its entirety. Whatever you are discussing is not understeer.

As to why, U has a higher natural frequency in yaw velocity/SWA, and is less damped. So while the driver of O is flailing about trying to get the nose of the car round, U is able to drive smoothly and get to the apex.

[venkyhere]

Most probably my flawed understanding stems from my interpretation of what you meant by the phrase 'step steer maneuver' - I imagine it to be like a zig-zag (one sudden step, then another sudden step with steering wheel), like a sudden lane change or a moose test, at high speed. Kindly clarify

[Greg Locock]

Step steer is an industry standard term for what I described in a previous post. You apply a fixed SWA and hold it.