Spooky55

I'm not an autocrosser, but feets' theory on lighter springs is sound and consistent with what I read in Chassis Engineering by Herb Adams (Pontiac engineer that designed the suspension on the Firebird and Trans Am). Lighter springs so the wheels can track the pavement better and heavier sway bars to control body roll and handling. I've modified my '78 Tans Am using his aftermarket parts (Herb Adams VSE) and theory and my TA can corner at around 1.0g with the original 15" wheels (and is a smoother ride than stock as well). There is a twisty road by my house and I can take it much faster in this car than any of the other cars I've had ('91 Corvette ZR1, '84 Porsche 944, '93 TT 300Z, '07 335i sport and yes, my C55). Although the Trans Am is a much older American muscle car and may seem apples to oranges, the C55 isn't that different overall - it's a nose heavy V8 powered rear drive muscle car regardless of who built it. I say give it a try.

Accidental L8 apex

I'm not convinced lighter springs up front as the only change will make the rear grip better than just removing the front bar. I'd think making the front more independent would increase front grip slightly while affecting the rear the least.

feets

Pretty impressive F body! Those things were known to be fairly floppy chassis, especially the T top cars.
I've had quite the soft spot for them, especially after Smokey and the Bandit was released. That happened when I was really getting interested in cars.

Herb has a pretty good book. It is in my collection along with Race Car Vehicle Dynamics and several others.

Removing the front stabilizer bar would indeed decouple the front corners but the drastic impact of loosening up the rear end would likely be far worse for rapid transitions. It would want to wag all over the place.

dorimaster

have no idea why you guys dont have the H&R swaybars!? but it eliminates the understeer COMPLETELY! those and the p30 brakes the car becomes a track monster, wider wheels/tires do barely anything(not getting into compounds). I out handle just about everything I've come across

feets

I honestly don't think you can get a big enough rear sway bar to take away the understeer experienced in autocrossing these things. You would end up with something so stiff it would essentially lock the two sides together into a solid axle.

Keep in mind that track days are a completely different animal than autocrossing. On a real track you have to be smooth and fluid to make the car turn low times. A really fast lap is almost boring to watch because there is no dramatic tire squeal or wild gyrations. In an autocross, smooth and fluid will guarantee you a last place finish. To give you an idea what I mean, take a look at the video my coworker caught on his dash camera:
Yeah, he got me by 0.43 seconds. That's what I get for taking a 26 year vacation from autocrossing.

dorimaster

you are WAY wrong, the car is perfectly balanced now, and the sway bars are adjustable! so you can custom tailor to your specific needs. I'll repeat myself this one last time(and have only been to the real track) sway bars, p30 brakes, and LSD, these cars will destroy ALMOST everything out there with these. GO try it before you come back and say it wont work(when its been known for nearly 15 years!!)

tjts1

Yeah, the car is obviously setup for safe, predictable understeer at the limit with most the weight on the front axle and all the grip on the rear. The clear solution to put rear tires on the front or go for a square setup. Don't go dicking around with sway bars and springs if you're not willing to adjust the tire grip.

feets

That's all fine and dandy.
It has been years since I drove real race cars on real race tracks. In fact, the C55 hadn't been released yet. I haven't had street cars on real tracks in quite some time but I've had them on private tracks such as Motorsports Ranch.

Still, screwing around at an autocross is a cheap and easy way to have fun in a car. It does require a totally different setup to be competitive.

Your perfect track day car might not do so well when things get really tight.

feets

Spoken like an internet hero with limited (or no) serious practical experience.

Super badass tires are a crutch. They can cover up tons of rookie mistakes and make a crap driver look good.
I could put RE71Rs up front and Super Sports out back to balance the grip but then I'd be tied to a tire combo.

The proper thing to do is to rough in the chassis on typical tires. Once it's giving you all it can you can put tires on it and be much faster than the guy who slammed stickies on it and went to the track. Those stickies just hide too many little things a driver needs to know.

Yes, it takes longer to properly dial in a car but the end result is far better than the instant gratification route that is so dominant these days.

Zeppelin

If you want lighter spring rates in the front then just look for some used C32 springs. They will be a little taller so if you don't like that look just cut one coil off them. You can also try adding another 1.5 degrees of negative camber to the front with 4 ( 2 per side) washers ( 10 cents each). You then just need to realign the toe.

I don't think you will ever get the car to where you will be happy with it on a tight autocross course. Wheel base is too long and too much weight up front to allow for low speed turn in ( at least for your given maximum front tire size). Good luck.