roll stiffness ratio

[Frank]

I am a little distressed at how tail happy our car is at the moment, and I'm wondering if anyone using Hoosier's could possibly give a ballpark figure of what roll stiffness ratio they are running.

I believe the numbers will be sensitive to other car parameters, WB:Track, castor, RC height, diff choice etc etc etc.

I would have thought it was probably going to end up a bit tail stiff ..... say F:R 45:55

Can anyone share some info?, it would be much appreciated

Frank

[murpia]

Normally a car with a rearward weight distribution (most FSAE) will be stiffer in roll at the front than rear. Exact numbers will depend on exact weight distribution, tyre sizes F&R, roll centre heights etc.

If you really have a roll stiffness distribution of 45% front / 55% rear, that would explain a tail-happy car.

Ian

[Frank]

"If you really have a roll stiffness distribution of 45% front / 55% rear, that would explain a tail-happy car. Ian"

Yes we do currently have that roll stifness distribution, and 5 sets of springs, and an adjustable swaybar, and yes the car is tail happy.

My question was what is YOUR roll stiffness distribution, if you happen to be using Hoosiers.

[This message was edited by Frank on October 24, 2003 at 07:26 AM.]

[ben]

Surely this is what testing is for?

Roll stiffness distribution is only one aspect of lateral load transfer distribution. To compare like with like you'd neeed RC heights and migration characteristics, track widths, and tyre pressures.

If you've got various different springs try and go to extremes, 60:40 50:50 and 40:60 that will easily show enough of a balance change to fine tune.

Ben

University of Birmingham
www.ubracing.co.uk (http://www.ubracing.co.uk)

[Denny Trimble]

Our '03 car:

Front Track 51.0 in
Rear Track 48.5 in
Tires: Hoosier 20x7 F/R

Weight Distribution w/ Driver: 46F/54R

Roll Moment Resistance:
55F/45R

University of Washington Formula SAE ('98, '99, '03, '04)

[Frank]

thanks heaps denny!!

perhaps we shall change the springs front to back and see what happens

we're just doing reliailty testing ATM, and are about to start the rough tuning process

I would have thaught the roll stiffness ratio was typically rear stiff, I shall try a little front stiff and see what happens

thx

Frank

[Frank]

ahhhh

F55:R45 all good now

thx again for setting my mind at ease Denny

[Denny Trimble]

No problem, good luck http://fsae.com/groupee_common/emoticons/icon_smile.gif

University of Washington Formula SAE ('98, '99, '03, '04)