Autocross setup

[CaliSting]

Ok so let’s say I don’t care about SCCA Street class and just want to make my GT2 RWD better for AX. Want to keep my car nice for commute so nothing crazy.

Here are mods in progress

Eibach springs and bars - purchased
RaceChip GTS black tune - installed

To be purchased:
19x10 rear wheels 21 lbs
19x9 front wheels 20 lbs

255 front 275 rear Bridgestone re71 r tires

Lightweight aluminum hat brake rotors

Lightweight CF hood

Ligttweight cat back exhaust

Figure this will shed over 100 lbs and more specifically get rotating weight down.

Curious are there some cost effective lightweight production wheels in 19x10 and 19x9? Wish tire rack wasn’t so conservative on fitment as they have great selection

 

[Kazz]

Sounds great! I'm waiting to hear more about wheels and tires, as well. Get as much rubber down as you can, meaning the widest wheels you can get and a wide tread.

Given preliminary info from only a couple of tuners, I think an upgraded intercooler will be a strongly recommended upgrade, especially for autocross/track, as well. And catch cans sound like the right thing to do.

 

[robz32]

You should also think about chasis bracing. Ultra racing braces will help stiffen up the rather flexible Stinger chasis, but you will also need a rear strut bar behind the rear seat to create a box section in the vertical plane as the Ultra racing braces stiffen the chasis on a horizontal plane.

 

[Kazz]

Yes, given not caring about class, bracing may become an obvious need in the coming weeks/months as more work is done with the chassis.

 

[CaliSting]

You should also think about chasis bracing. Ultra racing braces will help stiffen up the rather flexible Stinger chasis, but you will also need a rear strut bar behind the rear seat to create a box section in the vertical plane as the Ultra racing braces stiffen the chasis on a horizontal plane.

....Hmmm I didn’t feel much chassis flex yet and photos from my first ax show tires being held to surface very well without excessive rollover. I need to talk to other guy who tracked in nor cal with fat DOTR tires on Sonoma as that track will reveal chassis flex going up up hill. Think I’d go for firmer suspension bushings before adding any bracing and I say this as a guy who races caged Porsche’s and nissans . I know lots of people swear by bracing but I have had winning cars considered flexi fliers in comparison to Stinger with no braces at all. Maybe once I stiffen suspension up and get more grip i might feel need to brace shock/strut towers maybe?

.... I worry a little more about stock suspension arms moving around more than chassis right now but no one has come out with beefed up arms yet.

 

[Socalstinga]

@CaliSting do you use this car as a DD?
I’m over here upgrading springs and sways for fwy on and off ramps, street corners, and daily driving situations that might require some quick maneuvering lol #daddylife

 

[Helo58]

I KNOW they are not cost effective, but the Pilot Sport Cup 2 tires (24lb) shed about 6 additional pounds more per corner (over the 10+ on the wheels alone) over the RE-71/RE-11. I have found that Michelins are almost always lighter than Bridgestone/Firestone tires in any given class. You pay for it though. The RE-71s (30lb) are heavier than the current Pilot Sport 4S tires (27lb). These are the 275/19" tires.

As for bracing, your may not notice any flex in your setup now, but add wider tires and increase bar and spring rates and those increased cornering loads will get transferred to your chassis. A weak chassis will always act as a "fifth spring" meaning it will unpredictably flex in ways that prevent you from reliably making changes to your toe, camber, springs or dampers. You likely won't go wrong in bracing this car due to the weight and dimensions of it. If you are driving a RWD car, also do yourself a favor and pay close attention to stabilizing the rear during power application.

 

[GetYourWheels]

VS Forged wheels come pretty close to 20 to 22lbs per 19" wheel depending on the width and offset.

 

[CaliSting]

Interesting on Michelin tire weights. Problem with cups is they are under 200 treadwear. So if I wanted to run street class of some kind no go. And ps4 isn’t competitive to re71 in terms of grip.

On bracing again don’t think fairly narrow summer street tire setup with street springs and bars are going to create forces that will create much flex. Perhaps if I put big fat slicks on car with track springs and I were to go out to track where I could generate Gs to flex chassis.

Street class Ax setups usually benefit more from dropping weight. So I will start there.

Been setting up race cars for decades so have a good sense of what I need to do. Went with Eibach bars because they are adjustable so was planning on going full soft rear full firm front. That should help rears stay hooked up. Then dial alignment to get car to turn. Thinking a little toe out upfront with wider front tire should overcome bigger front bar. I do wish there was a good damper for the car but seems everyone is ignoring us. Maybe have custom set of Penskes made. Lol!

 

[Helo58]

Interesting on Michelin tire weights. Problem with cups is they are under 200 treadwear. So if I wanted to run street class of some kind no go. And ps4 isn’t competitive to re71 in terms of grip.

On bracing again don’t think fairly narrow summer street tire setup with street springs and bars are going to create forces that will create much flex. Perhaps if I put big fat slicks on car with track springs and I were to go out to track where I could generate Gs to flex chassis.

Street class Ax setups usually benefit more from dropping weight. So I will start there.

Been setting up race cars for decades so have a good sense of what I need to do. Went with Eibach bars because they are adjustable so was planning on going full soft rear full firm front. That should help rears stay hooked up. Then dial alignment to get car to turn. Thinking a little toe out upfront with wider front tire should overcome bigger front bar. I do wish there was a good damper for the car but seems everyone is ignoring us. Maybe have custom set of Penskes made. Lol!

I have never been autocrossing and I enjoyed learning that classes have specific UTQG limitations. I guess going below 200 would put you in a class you wouldn't be very competitive right? With a little research, I found that the the RE-71 is the go to tire for Ax. Good to know. I do have a question though, how do Ax guys get their tires up to temp? Warmers? On a road course, your tires get up to temp over several laps. With Ax there is no "warm-up" time, but I guess everyone is in that same boat so it doesn't matter??? Is that why the RE-71 is so beloved in Ax?

Also, your initial bar setup, as you described it, will move you towards understeer right? There are just so many combinations of adjustments from tire pressures, widths, camber, spring rates, damping rates, sway bars, toe, etc., that finding the sweet spot would be quite an accomplishment.

Best of luck with this. I look forward to seeing what you do with the car, especially with respect to the handling. It sounds like you are off to a good start. BTW, I hope you saw in another post above that there is a 20-22 pound 19" wheel for our car. That would be fantastic!

 

[CaliSting]

RE71s get up to temp pretty quickly faster than some race compounds. We also at national level run co drivers. First driver is usually slower of two. 1 st run is to get tires up to temp. No tire warmers.

For race car classes we use very soft compound race slicks. Similar to a qualifying tire or wet compound but even softer.

Nice thing about stinger is car rotates very nicely with trail brake and power out of turns. I’d love adjustable dampers to help in setup. I have a crazy Porsche hill climb car with JRZs, gt3 cup car suspension , all easily adjustable and I can usually adapt to different surfaces just with more bump etc.

Stinger is tougher as I’m limited to bars adjustment and tire pressures.

Us AX drivers get real creative! Stuff road racer would just shake their heads.

I have lots of track experience as well.

 

[Kazz]

I'm very interested in what you find out about alignment options. I'd like to dial in more negative camber but it sounds like that's not easily done.