May 2005
Scrub radius is taking a projected line  through the center of the king 
pin to the ground, then taking the center line of the wheel,not where the 
mounting is, it has to be centerline. Project that to the ground, the 
distance between the 2 lines is the scrub radius. The closer to 0 you get 
the better the car steers at 0 it is like power steering ,that's why when 
people put deep dish wheels on it steers heavy. Stude did some crazy 
stuff on their suspension if you look at the specs. in the manual you 
will see that when you turn the wheel 20 degrees one way the opposite 
wheel only turns 17-18 degrees you now have 2 to 3 degrees toe out.That 
is the reason for the odd ball feathering on the inside of the tire and 
when you have the  tires slightly out of ballance and the shocks a little 
worn you get a little cupping with it too.Also clamped springs the Stude 
HD springs for the 53 Commander are M52627 they have an installed spring 
rate of 270 lbs. inch I have checked this my self on a spring tester.The 
spring rate formula is Rate=Gd4 divided by 8NaD3 where G is the modulus 
of elasticity in torsion (11,500,000 psi for steel) d=round wire size 
NA=active coils only(excluding any end or dead coils. D=mean body 
diameter(od-d or id=d) you will see that the Stude has a 14" free 
standing height and a 10" installed height with the lower a arm parralel 
to the ground. When you take and clamp the coils you kill atleast 2 
active coils the rate jumps to 527.85 lbs inch.I could go on and on about 
Stude Ackerman but that's another story.
             
                      AJ