I wanted to post up some discussion I had with Bob that might help some other people using the program:
I asked:
On the dynamics page it seems that stiffer = grip, I'm assuming this is just a result of the formula, is there a way to relate weight transfer into that? For instance when I change my spring rate 50% I have to expect xx% less weight transfer to that given corner.
Bob’s response:
Actually softer will develop more grip than stiffer on the basis of Lateral Load Transfer (LLT). If you watch the 'Suspension Dynamics" screencast video on the website and/or read the Dynamic Page Help file LLT is explained in detail there.
A stiffer setup will be more responsive but may have less total grip than a softer setup. The reason being that under the right circumstances the chassis CG will actually drop if you reach the limit of your droop settings in roll. You can see the effect by changing your droop settings and watching the animation carefully or looking at the graph of CG position versus lateral G. When the CG drops the LLT from the inside to outside tires is reduced. A pair of tires with less difference in load between the inside and outside tires will develop more grip.
Dynamics Youtube video:
http://www.youtube.com/watch?v=G6n1d1g0_qE&feature=plcp
Next I asked about chassis roll:
In the roll angle vs Lat G graph you have about 3dg of roll, if my maths are right a normal TC at 5.5 ride height and a 90mm chassis should have almost 7dg before contact is made (triangulating the plane under the chassis) I'm not sure what you are using for the dg of roll measurement.
Bobs response:
Regarding the chassis roll question. The roll versus lateral g graph shows how much the chassis rolls at the maximum lateral g value entered. The simulation rolls the chassis about the dynamic roll centre until the maximum g level entered is reached. If you want the chassis to roll more enter a higher lateral g value in the box. The simulation will run until the lateral g valu7e entered is reached or the chassis contacts the ground whichever comes first. Your 7 deg calculation is correct for chassis roll about the mid point of the chassis. The maximum roll angle achievable will be different when rolling about the roll centre and with droop effects considered.
I admit that I never read the help page in the program, but I looked at it, and it is very helpful, for example:
Lateral Load Transfer (LLT) versus Lateral g – LLT is the amount of load that is
transferred from the inside wheels to the outside wheels during cornering.
So to minimize the LLT you want to reduce the car weight, lower the CG or increase the
track width. Ok so why would you want to reduce the LLT. The reason is tires. Consider
two load cases with tire pairs both carrying the same total loads. In the first case the
tires carry close to the same load (low LLT) and in the second case the tires carry
significantly different loads (high LLT). Because of the way tires convert vertical load
into lateral grip the tires with similar loads in case 1 will produce more grip than case 2.
(couldn’t paste the pictures).