View Single Post
Ranger Mike
Ranger Mike is offline
Jul30-09, 02:53 AM
Sci Advisor
PF Gold
P: 1,418
Ok, here is how we determine the proper springs for each corner of the race car. you asked about loads on each wheel..well here is an example of our old door slammer running on a medium banked asphalt track.
Stock suspension with solid rear axle.
We calculated that it is under 1.3 Gs in the turn. " F= ( m*v^2 ) / R " is correct formula
one more piece to ponder..

from our cone killing days in SCCA Autocross..skid pad testing ,,go to parking lot, airport,,what ever, set up circle 200 to 300 feet in diameter, drive around the cirle as fast as you can without spinning out..
G = 1.225 x R / T squared
R= Radius of the turn in feet
T = Time in seconds to complete a 360 degree turn

typical Corvette corners at .84gs
road race sedan like Tran Am 1.15 Gs

if you know the tire performance curve from the manufacturer charts weight (vertical load in static pound) vs Traction (lateral load in lbs) you can calculate the Cornering efficiency.

This particular car weighs 2800 lbs. of 35% of weight will transfer under 1.3 G
and 75% will be on front end due to engine weight and corner loading

2800 lbs. X .35% = 980 lbs. transferring or loading tires

75% of 980 lbs. = 720 front end weight
divided by three to determine wheel rate ( two front springs and sway bar )
so we need wheel rate of 240

Wheel rate = (Length of A-arm divided into inside frame mount point to center of spring mounting point) squared

times spring rate

now the hard part
get out the tape measure and measure bottom front A-arm length
1. inside frame mount point to center of outside ball joint
2. distance from inside frame mount point to center of spring mounting point

stock Chevy A-arm is
16.5 inch inside frame mount point to BJ and 9 inch from inside frame mount point to center of spring pocket
assume you have a 800 lbs. spring
wheel rate = 9 / 16.5 = .54

.54 x .54 x 800 = 233 lbs. spring required to handle weight transferred

run a little stiffer sway bar and tune from here..
Chances are the Gs are off a little but we need a baseline t ostart andthis is as good as any.