Wrong calculation of rolling resistance

[LBodnar]

Please bear with me. We will go through this mess together!
It's more complicated than it looks. Genta never made it clear in his book for whatever reason. Let me know if you understand what I am saying.

1) In any tyre speed-dependent part of rolling resistance only starts acting above tyre's rated maximum speed. The discussion in Genta's book is purely theoretical - you are not supposed to ever achieve the speed at which V^2 term is relevant. This is where tyres start heating up and self-destruct. So for the sake of real life driving we assume rolling resistance independent of speed.

2) There are different definitions of slip ratio. If you define slip radius centre as lying on the track surface then Fx cannot generate any torque (arm = 0) and rolling resistance torque needs to be defined separately from Fx.

3)The way slip radius is defined in Pacejka works it ends up lying under the track surface. Thus Fx can be adjusted to account for rolling resistance torque. Pacejka magic formulas (at least 1996 and 2004) have speed-independent part of the rolling resistance (fo term) already embedded in Fx formula in the form of Sh term. This Sh term shifts the whole curve left by the value of "free rolling slip." In other words at zero slip Fx(0) = Fr = rolling resistance.

So basically if you are using correct Pacejka formulas and feed them with correct data then you don't need rolling resistance per se.

However!!! Somebody did this:

// horizontal shift
btScalar Sh = 0; //beckmann// b[9] * Fz + b[10];

:o

4) Where did you get "touring" Pacejka data from? It produces free rolling
result Fx(0) / Fz = 0.12 which is 10 times higher than it should be! Maybe this is why it has been commented out? Genta has two reasonable sets of Pacjeka 96 data for family sedan and sports car tyres that look good.

My suggestion: remove rolling resistance torque from cardynamics.cpp, reinstate Sh and triple-check the origin of Pacejka data for "touring" compound, namely b9 and b10.

Thanks
Leo