Not to play one-upmanship, but I emptied some pennies as well....
Penske 7500DA...just go ahead and give up now, because everyone knows that Penske only supplies winnars, y0!
(Just kidding, of course.)
If I did the math correctly I measured the front and rear MR at about 0.7, confirming the online values. To get a front natural frequency of about 2.5ish and rear NF of 2.3ish the wheel rate is about 400 lb/in (I say "about" because I haven't confirmed the published weight of the car, and assumed an unsprung weight of approximately 60lbs per corner) Since the springs are angled, the effective rates are closer to 93% of actual spring rates (need to confirm the actual shock angle though, I approximated 70 degrees from horizontal). Also, using stock rubber bushings adds some chassis compliance, so having slightly stiffer spring rates is justifiable to counteract that. I ended up going 800/700 2.25" springs, 7" front and 6" rear. Speaking at length with Penske, they thought that a longer spring at a higher rate could result in bottoming out the lower spring perch. I went with 2.25" to ensure adequate tire clearance, and the Penske folks said the availability of rates was sufficient with 2.5s but exhaustive with 2.25s.
Like Jeremy said, springs are cheap relative to shocks.
Fingers crossed everything gets here in time for the Feb TnT, although the drive down may be a bit lively....
_________________
Steve Carter
1972 Datsun 240Z-- resto pics at
http://picasaweb.google.com/srcartermd2007 GPW Honda S2000-- STR 86