adrial

They will not effect the amount of weight that is transferred. A swaybar acts as springs that only really work when you are cornering.

If you had a mushy front end, the front end would (obviously) drop more than with a firm front end under braking. The time it takes for the car to reach full dive (in the case of braking) is controlled by shocks.

Manning

I understand anti-sway bars are for roll control. Your comment was that springs/bars do not effect weight transfer, but in fact they do. If you have a lightly sprung front end, then the front will dive more radically under hard braking and the weight will effectively transfer to the front of the car. Shock valving will help control the initial dive and how quickly/rapidly either end of the car rebounds. Rebound valving in the rear can play just as important a roll in transfer to the front end as compression damping in the front does.

adrial

Weight transfer is just (Accel * Static weight * CG height)/wheelbase (or track for cornering)
Use units of G's, lbs and a consistent measure of distance (ie feet or in....whichever juse use it all the way through).

Unless we're talking about extremely severe angles here I dont think that the amount that the car dives/rolls has an effect on weight transfer.

Manning

OK, so then when you brake into a turn or even just turn in there is no appreciable impact on weight transfer imparted by stiffer or lighter springs? (I am including bars and shocks here since they do impact effective spring rate) I don't buy that. Considering how much you can effect handling by corner weighting/jacking a car, and considering the fact that either end/side of the car can dive or lift several centimeters while braking or turning in, how do springs, etc. not impact weight transfer?

EDIT I am not implying that the amount of weight transferred is greater or less as a result of springs, shocks, bars, tire stiffness, etc. I am saying that the direction of transfer is impacted. The amount of weight is impacted by acceleration.

Serge944

Very true. I was definitely referring to a street car as that is the only place mine is used. This is true for 75% of this board as well.

I was merely trying to point out that increasing springrate is only a compromise solution for an dated suspension design.

Take it easy.

Serge944

It has an INCREDIBLE impact. Why do you think running biased springrates caused under/oversteer?

adrial

I'm just learning all this stuff myself, but this is my understanding...

If you draw up a diagram showing the forces acting when you accelerate/decelerate in any direction... you can see where the equation comes from if you sum the moments about a corner of the car (when looking at only half the car...ie only front, or only the right side...)

This website does a decent job of explaining.. http://phors.locost7.info/phors01.htm

The change in angle of the chassis due to dive/roll I think is negligible.

Stiffer springs/sways are great for quick directional changes and keeping camber change due to body roll in check. There are some threads on the racing forum that can probably explain this way better/more correctly than I or that website can.

adrial

Because the stiffer sprung side has less traction.

adrial

Imagine taking a monkey wrench to a big pipe coming out of the back of the car...and applying a load that would produce the same bodyroll that a 1G corner would.

Say the rear is real soft and the front is nice and stiff.

The rear will want to just fall over while the front will put a stop to it...in this scenario the car will understeer under steadystate cornering.

That is my understanding anyhew... I am sure there are others that can explain what I am saying much better.

Manning

I've only glanced at this page, but it seems to bear out what I am saying

http://home.tiscali.be/be067749/58/c4/

Are the physics incorrect?

EDIT not only does it bear out what I am saying, but it does so with almost the same wording I used in the edited bit I put in my post above. Frightening coincidence.

adrial

I think the wording is a little misleading...but I may be wrong.
Like I said I'm just learning this stuff myself so its difficult for me to explain what I'm thinking.

To really explain whats going on in weight transfer/understeer vs. oversteer characteristics of a 4 wheeled vehicle with real numbers...things get complicated.

Serge944

The softer the springs, the less load is transferred onto the outside wheels. But obviously, a stiffer spring will not only increase the load transfer, but will also decrease the lean.

Its not the lack or roll that causes more optimal grip...its the fact that less weight is absorbed by the spring, instead of being transferred to the ground.

The lack of lean is merely a by-product. I can see how it can be misleading though.

So I think that I agree with adrial.

Manning

Try this one on for size then.

http://www.advancedracing.com/produc...rtchassissetup

adrial

I think I'll take a 24 hour break and regroup my thoughts.

Here is yet another link...

http://www.grmotorsports.com/swaybars.html

"A firmer anti-roll bar in the rear will increase the rate of lateral load transfer, placing more demand upon the rear tires, accelerating lateral traction loss and creating more oversteer, holding all else constant."

Another one... http://www.rqriley.com/suspensn.htm
"An oversteering tendency will be reduced by locating the anti-roll bar at the front where it will reduce the cornering force and adhesion of the front tires. "

The net result of traction is the same, but how it is explained varies a lot. Most of these things we'll find online are probably dumbed down for the public.

I think if we search hard enough we can find a link that proves that pigs can fly and are actually superior beings plotting to make their move to take over the world!!

luckett

Come on guys! You're engineers. Break out the math and show a proof!