Norm Peterson

First off, power sliding through corners may look and feel impressive, but it's slow and has greater potential for going ugly in a hurry. The smoother you can get your steering and pedal inputs, the better off you'll be (and the faster your progression at really driving hard will be).

Mechanically, it's tires/wheels before everything else in terms of potential. That's not to say you have to wait intil the current tires are completely dead before upgrading anything else, just that tires are ultimately where it all happens.

The '08 GT isn't all that bad out of the box (I've got one), but after at least 4 years and 84000 km your shocks and struts aren't what they used to be (and they weren't all that great on real-world roads anyway). The "floaty" issue you mentioned is mostly these, and the go-to answer for this for most folks with an interest in hard cornering is the Koni Sports (aka "yellows"). There are other shocks/struts further up the food chain, for considerably more money.

A moderate increase in spring stiffness combined with no more than moderate lowering will help, but don't get carried away with the appearance of "lower" always equalling better cornering because that just isn't always so. There are suspension geometry issues as you lower much past 25 - 35 mm that kind of chip away at the improvement that the increased spring rate is trying to make. Know that a 1" (25mm) lowering only reduces the lateral load transfer onto the outside tires by maybe 5%, which isn't a huge effect until you're trying to shave small fractions of a second out of measured run or lap times in competition.

A little more roll stiffness, plus the ability to tune front suspension roll stiffness vs rear suspension roll stiffness, should be part of your plan. You're looking for both the front and rear stabilizer bars to be at least 3-way adjustable.

Alignment - camber that's somewhat further negative than the -0.75° factory preferred setting helps. However, as you push this much past maybe -1.25° you'll start needing to corner a bit harder than average traffic most of the time and/or start entering autocrosses and occasional track days.

For track days, you'll absolutely need better brakes. Maybe the first outing or two on a track that's easy on brakes you might be able to get away with street performance pads, but don't take that as a recommendation to do so. Don't ever forget that you're almost racing.

I'll throw up a couple of pictures taken earlier this year just to illustrate where only a few mods can put you. My car has Koni yellows, Strano bars with better endlinks up front, Steeda HD strut mounts, and a very aggressive (for street) alignment. Tires are only 255/45-18 on 18x9.5 wheels. Stock springs.

Here I was running only about 0.4 second slower run times than an '02 Corvette entered in the same event.




Out on the big track it was a different story, it being my first time out there (I was consciously taking it a little easy in the braking zones) and I know I was giving up speed on the straights to the 'Vette (immediately behind me). But the only car that lapped me was a sponsored stripped and fully caged almost-real-race car (that is right behind the 'Vette).




Norm

kevilay

Thats some great info. Thanks for such a detailed write up. Im glad that lowering it isnt as effective as I thought. My car is already low enough in the front with the gt500 front end. Looks like I got some work to do!