Thanks again for taking the time to help me improve the book.
Caster: If you are getting more steering at corner entry and mid corner, then it sounds like your are simply finding the optimum caster angle to give you the optimum camber angle in the corner, given the static camber you already have. As you clearly understand and as I point out in my book, you can take adjustments too far and actually get the reverse of what you are looking for. This is an important point to remember. For example although in general if you want one end of the car to grip more then you soften the suspension at that end of the car. However if you soften it too much you will actually loose traction. The concept of going too far with an adjustment and getting the opposite results is why I was not surprised that you were getting results that differed from my book.
If it is only the initial turn in that gives you more steering then as I discuss in my book, less caster can give you more initial steering. Less caster will give you a much quicker initial steering response because you keep a larger contact patch of the tire on the ground during this initial turn-in point before the car reaches the extent of it’s “roll”. When the car does reach the extent of it’s “roll” however, you could end up with a smaller contact patch with less caster and this is why you might have less steering during the middle or end of the corner.
Kick-up: I went back and checked the diagrams. You are correct, there is a "typo" in the kick-up diagram. The "Positive Kick-up" diagram has some text saying "towards front of chassis", and it should say "towards back of chassis". Time to fire my editor eh!
. Sorry about the error and confusion. This will be corrected, thank you. Although I did intend the text to say "towards back of chassis", I have run negative kick-up at the advice of David Spashett at a foam tire race earlier this year.
Toe and Ackerman: Yes it is true I did not include an explanation of Ackerman. I already have plans to include this and other topics such as tires and inserts in the next version.
Over Simplified Explanations (e.g. shock angles): This is a tough one to balance, as different readers like different levels of complexity. You are correct that in general layed down springs do change their compression rate more than stand-up springs. However, for most cars, layed down springs are more progressive in their compression rate and thus get stiffer as they are compressed. This is because as the lower “A” arm starts to lift up, then the force against the spring is getting closer to the plane the spring is on.
In addition to adding something that talks about the above paragraph, what do you think about adding the following concept to this section on shock angles/springs? It provides a more complete explanation of why layed down shocks are softer.
In my "simplified" explanation I suggest that a layed down shock gets compressed less and thus is softer. There is actually more to it than that as this explanation does not always hold true when the springs have truly constant linear spring rates. I have talked with some engineers about this and the way they explained it to me is as follows. When a spring is vertical (lets call this vertical plane the Y-AXIS), then the entire force of the spring pushes against the Y-AXIS force that is compressing the spring. If however the spring is layed down then only a portion of the springs force is applied to the Y-AXIS force that is trying to compress it. This is because the force of the spring is now split between the Y axis and the X Axis. In other words the more the compression force is on the same plane as the resistance force of the shock/spring the harder the suspension will be.
I was also thinking of adding some content around progressive spring rates.
Thanks again for your help in making this a better book.