Re: Suspension

[Dave Dahlgren <ddahlgren@snet.net>]

Has anyone taken the time to calculate the moment arm between the CG and roll
axis?? If you are getting chassis roll with the car standing still revving the
engine or with an under .5 G accel rate me thinks there is some very basic
design work not done yet. All a anti roll or sway bar can do is take bite away
from one end of the car, it couples the motion of one wheel to the other. I have
owned cars with a lot of sway bar and they are a nightmare to drive at almost
any speed. Most of the cars I have seen have the roll center in the rear way too
low and that probably has a lot to do with the chassis roll. The old moment arm
thing again. You can build most anything in your garage but it does have to be
engineered correctly for the application, not just connect the mounting points.
The word application is important as a drag race setup has nothing to do with a
road race that has nothing to do with a circle track that has nothing to do with
a Bonneville one either..This is not the sort of thing that is way right of the
decimal point either it is to the far left of it. Before you can make any
intelligent decisions about your cars suspension see if you can answer the
following questions about your car and the suspension in general. Here is a
short list...

My front and rear wheel rate is?
My motion ratios front and rear are?
and are they the same left and right side?
My CG is where?
My front roll center is where and how would i change it?Why would i change it?
My rear roll center is where and how would i change it?Why would i change it?
My instant centers front and rear are where and how or why would i change it?
What wheel rates do i need in order to control chassis attitude during a run?
What is the sway bar rate if so fitted.
When or why would i want to change it?
When i do change it how does it effect the corner weights dynamically?
What forces in general are acting on the suspension during a run?
What about the the ones at each wheel during accel and decel and steady state.
What do i need to do for more traction?
What are the corner weights of my car?
How do i know it the chassis is too soft or too stiff and is it the shocks or
springs or suspension points binding?
My moment arm between the CG and roll axis is? What is the effect in changing
it?
Dave