I have been thinking about "Wheel Rates" v "Spring Rates".
I can see this calulating wheel rates form spring rates could be a very comples calulation.
However, I think we might be able to get close enought to use for comparisions if we apporach this in a more simplistic way.
Here is what I am thinking:
The front seems easy. If we look at the front the wheel goes up and down very evenly with the strut. Thus, the spring rate and wheel weight for the front should be prety close to the same. The length of the A arm is mostly irrelivant as all it dose is locate the strut.
The rear is a little more complicated in that the shock is mounted a little over 4" past the centerline of the wheel. The wheel center is about 18.5" from the center of the spring plate arm link. Thus, the rear shock point moves foughly 15% furtner than the wheel at any time. Thus, the rear wheel rate should be about 15% higher than the rated spring rate.
Elephant Racing now offeres coil over kits for 911's and has a spring rate calulator depending on use and weight.
See:
http://www.elephantracing.com/suspension/coiloverkits/911coiloverkits.htm
For a 911 of my weight on a full race car they are recomending a starting point of 400front/550rear.
If my assumptions as to how we might convert spring rate to wheel rates, that would put me at about 400# front and about 630# for the rear "wheel rates".
For compairison I belive the wheel rates for a 23/31mm torsion bars is 250/332#.
Thus, 400/550 rated springs should be about 60% stiffer.
Here are what I belive to be the wheel rates for different torsion bar sizes as being:
Front: (lbs/inch) (% of stock)
19 110# ---------(18.8mm)
21 173 157%
22 210 191%
23 250 227%
24 290 264%
Rear
24 122# ----------(24.1mm)
25 140 115%
26 165 135%
27 191 157%
28 221 181%
29 254 208%
30 294 241%
31 332 272%
33 427 350%
Note that rear TB was 24.1mm till 86 then 25mm. 930 rear's were 26mm.
I would like to know if this is close to being valid and appricate input.
Thx.
