Originally Posted by
Kensei
Bought the book and studied it.
The way you explain roll center I understand.
As I understand it you can change the height of the roll center by moving the inner upper pivot point.
However I hear and read about changing RC by putting shims in between chassisplate and the mountingblocs of the suspensionarms.
For instance: what does the RC do when adding shims?
I hear people say that RC is raised then. Is that correct or not?
I don't quite understand. Because adding shims leads to heigher inner pivot points which would suggest a relatively lower roll center (your book page 61). But maybe I am wrong here. By adding shims not only the upper inner pivot link raises but also the lower.
See my problem?
- people tell me that adding shims leads to a higher RC
- I thought that it lead to a relatively lower RC, because the inner pivot point are raised as a result of the added shims
In the book you say:"With low traction tracks you will want the car to roll more to increase traction."
I race at low and medium traction tracks. So I would say my RC would have to be low to increase traction. In that case I would add shims.
Christopher Krapp, Kyosho TF6 teamdriver, told me he had 2mm shims added on outdoor tracks and 1mm on indoor (carpet) tracks.
I understand that as that indoor (carpet) is more traction and therefore less roll is needed/wanted, therefore reducing the roll center of the chassis is needed and that means that the roll center has to be higher. He does that by shimming less.
However I read a Testreview on the Kyosho TF6 where the tester raced with 2mm shims and said that the car didn't roll in the corners and had to go to 1mm shims.
That is a contradiction I think. That is if more shims equals lower RC ecquals more roll.
to hopefully clarify this for you,... if raise the inner upper link pivot point you lower the roll center. If you raise the lower arm inner pivot point you raise the roll center.
Regarding the quote from my book....what I meant to say is that by having softer springs on low grip tracks it allows for more weight transfer to the front and rear of the car during acceleration and braking and initil turn in, thus giving you the ability to control the balance of the car more with the throttle.
To increase lateral grip you want to minimize the amount of lateral weight transfer (optimizing the grip efficiency of the tires). So it may seem odd to have softer springs on a car as this will actually reduce the lateral grip. Remember that lateral grip is different than balance and by having longitudinal weight transfer (or pitch) you can better control the longitudinal weight transfer using throttle and braking...thus giving you more control over the balance of the car.