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Rob 930 Rob 930 is offline
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Join Date: Dec 2002
Location: Seattle
Posts: 659
David,

Yes, I'm happy with the setup, but I don't have much of a basis for comparison because I haven't experimented much with other spring rates. I will say that it feels very good -- stable, predicatable, and surprisingly forgiving (at least in terms of the suspension). The only aspect of its performance that's the least bit spooky is the nonlinearity of the power onset. It's not lag, exactly; I don't feel that at all. It's the fact that if you give it 50% throttle, you'll get 80% torque. At corner exits, that can be a problem, so the default has to be a very conservative use of the throttle until the car is fairly straight. That's why cars like that RSA can do so well against so much power - strong N/A cars can gain an advantage at corner exit because they can build up speed after the apex with more confidence. But on a lap to lap basis, and certainly down the straights, the 930 is hard to beat. Only the most powerful N/A cars, like the new Z06, can compete in the straights. Of course, driver skill plays a huge role too; the RSA in that video is piloted by a top local driver and he's been driving and developing it for years. I do a lot of driving, but mostly in a 944, and I've only logged 6 days on the track in this car. Each day I make changes and improvements to the car and I experiment with my technique (and nerve), but it takes a while to extract maximum output from a car like this.

As for spring rates up front, I've been told that 23 mm is the absolute largest you want to go, ever, with torsion bars. The explanation I got was that the control arms themselves can't handle more spring than that -- that they may distort if the T-bar gets too stiff. I don't know if that's true or not, but if you're considering 24s, you might ask around. Also, I haven't felt the need for more front spring. As for rear springs, I ran it twice with just the 31 mm T-bars (no helpers), and I felt that with this much power I was getting squat and undesirable weight transfer that was causing the car to understeer when throttle was applied. The helpers cured that, or seemed to. Trouble is, I didn't make that change independently of other suspension adjustments (I also increased the rake when the helpers went in), so I can't really assess the improvement purely from the rear springs.

Some people think of the 930 on the track as a mean and nasty machine that will bite you at every opportunity. Though it's a bit gnarlier than lesser-powered cars, it's surprisingly docile and forgiving. Having huge tires helps this. And to drive it is a real sensation. The feedback it gives you is incredible.

Rob

Last edited by Rob 930; 01-25-2010 at 09:13 PM..
Old 01-25-2010, 06:19 PM
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