track suspension info needed... Options

[Jeroen]

Hey all,

Gathering suspension parts for my track car and I'm trying to make up my mind

I'd like to go with yellow adj. Koni's.
Does anybody now up to what spring rate the yellow Koni's can handle?

Should I go for torsion bars (22 or 23mm)
I can have the struts modified for coilovers for about the same money I'd need to spend on the t-bars
Coil over springs are pretty cheap and I wouldn't be stuck with just one spring rate

Any info on springrates in relation to the weight of the car?
I'm aiming for about 1750# for the car and was thinking about starting with 275 or 300# rear springs

Does anybody know the spring rates for the front torsion bars?
I've been looking into it, but different sources quote (very) different rates (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif)
Anybody running big front t-bars (22 or 23mm), what springs are you using in the rear?

I know, lots of questions, but I'm trying to figure out my options, so any advise is welcome
Right now I'm looking at too many unknowns to make a decent guestimate

thanks...

Jeroen

[lapuwali]

I've never really spent much time on car suspension, but I spent a ton of time and money on bike suspensions. The key issue there was getting the answer to Ben's question: spring rates for the available shocks. On a bike, anyway, these always had to be considered as a pair. If the shock wasn't adjustable, there was a fairly narrow range of spring rates that worked. Go outside of that, and the shock could no longer control the spring (if too high), or the damper set the performance more than the spring (if too low). A too low spring rate relative to rebound damping also got you a jacking effect, where the spring wouldn't fully extend the shock again after compression, and a series of bumps would give lower and lower ride heights until the shock bottomed out.

The mass being sprung and damped mattered, but was essentially the same for most bikes (the rider made a bigger difference than one bike or another, assuming the same rear suspension design). I would expect Koni or Bilstein could provide these numbers, esp. on a simple coilover setup like the rear of the 914. For the front, they'd need to know the geometry of the system to get the effective rate of the torsion bar at the damper.

btw, wild guess here, but the two lists of torsion bar to weight numbers might be wheel or damper rates, which are probably different front/rear on a 911 (different length of lever arm between t-bar and damper or wheel). A longer lever gives a lower effective rate for a given size torsion bar.