Suspension Question

[ChitownStang]

So I need a little help on my suspension setup.
I have a 15 - non pp gt that I have installed oem pp springs, Steeda fixed pro-actions, Bushing support/centering system, IRS support brace. I've also done some front stiffening with oem pp strut tower brace/upper and lower k-bracing and I run staggered 19" summer tire setup.
My issue is when aggressively cornering, pushing the car to the edge before loosing traction, the car feels a little wiggly and unstable. What do I need to do to be a little more stable and composed without adding NVH?
I am on stock GT sway bars, is this my weak point?
Keep in mind I'm not a racer but I do drive aggressively where it's safe and I want to enjoy my sports car. I've spent a lot of money on the suspension so far and I think I'm close, but I do not want to lower or make the car less comfortable than I already have so I'm walking a fine line here, I know.
Thanks in advance for any advice.

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[BmacIL]

So I need a little help on my suspension setup.
I have a 15 - non pp gt that I have installed oem pp springs, Steeda fixed pro-actions, Bushing support/centering system, IRS support brace. I've also done some front stiffening with oem pp strut tower brace/upper and lower k-bracing and I run staggered 19" summer tire setup.
My issue is when aggressively cornering, pushing the car to the edge before loosing traction, the car feels a little wiggly and unstable. What do I need to do to be a little more stable and composed without adding NVH?
I am on stock GT sway bars, is this my weak point?
Keep in mind I'm not a racer but I do drive aggressively where it's safe and I want to enjoy my sports car. I've spent a lot of money on the suspension so far and I think I'm close, but I do not want to lower or make the car less comfortable than I already have so I'm walking a fine line here, I know.
Thanks in advance for any advice.

Where are you losing traction? Front, rear? Both? Where in the corner: entry, middle or exit? You have just the alignment dowels and the braces from Steeda, right, not the subframe support system?

Usually in this case I always ask about alignment, tire pressures first. You did the Steeda struts in addition to the rear shocks, yes?

 

[ChitownStang]

hey Brian,
yeah I have the proaction fixed shocks and struts and the entire Steeda stop the hop starter kit which includes the subframe support braces.
instability seems like it's in the rear, front seems really solid.
I feel it entering middle of the corner where most g's are.
Car has been aligned since suspension was done. Tire pressure 33-34psi cold

 

[BmacIL]

hey Brian,
yeah I have the proaction fixed shocks and struts and the entire Steeda stop the hop starter kit which includes the subframe support braces.
instability seems like it's in the rear, front seems really solid.
I feel it entering middle of the corner where most g's are.
Car has been aligned since suspension was done. Tire pressure 33-34psi cold

Can you send me (text) or post your alignment? I'd also start your pressures lower, particularly the rear, at around 30-31 cold. So it's entering the corner, off-throttle you have rear instability? Braking or no?

 

[ChitownStang]

Unfortunately I do not have alignment #'s, local Midas did it and I did not ask for it like a dumbass. I doubt they keep these records but I can ask.
I can try lower rear tire pressure.
I feel it on or off throttle, no braking.

 

[BmacIL]

Unfortunately I do not have alignment #'s, local Midas did it and I did not ask for it like a dumbass. I doubt they keep these records but I can ask.
I can try lower rear tire pressure.
I feel it on or off throttle, no braking.

Ah ok. Yeah see this is the rabbit hole: when you modify the suspension and get rid of a lot of the rubber deflection, very small differences or discrepancies in alignment can make a large difference in handling. If you can get the sheet it will be helpful, but otherwise I'd strongly suggest getting at least an alignment check at a place like Firestone, so you know where you're at.

 

[ChitownStang]

LOL, suspension is the biggest rabbit hole ever!

 

[Roadway 5.0]

My issue is when aggressively cornering, pushing the car to the edge before loosing traction, the car feels a little wiggly and unstable. What do I need to do to be a little more stable and composed without adding NVH?

Do you experience this instability during all turns, or maybe just on your favorite turn to take fast while on your daily driving route? I only ask as it may be an oddity in the road (sudden depression/taking a big bump sideways).

Other than that, I agree to check your alignment. If you don't have enough toe-in on the rear wheels, then the car can become a wild beast. 0.12 for each rear wheel is a common solid number and is what I run on my car.

 

[ChitownStang]

It's on any curve that I take fast. The alignment is probably stock specs as I didn't tell them to do differently. I guess I will need to have it checked. Looking at tires from behind the car looks like they have slight toe in on rear but hard to tell.

 

[ChitownStang]

What are the alignment specs that I would need to give a shop if I had it redone?
Again, I don't want too extreme where I will have uneven tire wear or other issues. Car is driven in winter as well with 235/18's wheels and winter tires
Thanks

 

[BmacIL]

What are the alignment specs that I would need to give a shop if I had it redone?
Again, I don't want too extreme where I will have uneven tire wear or other issues. Car is driven in winter as well with 235/18's wheels and winter tires
Thanks

My recommendation would be the following, though front camber and caster are going to be where they are for you without plates/bolts:

Front
Camber: -1.4-1.5
Toe: 0.02 to 0.05 per side (slight toe in), 0.00 steer ahead

Rear
Camber: -1.2-1.4
Toe: 0.10-0.12 per side (toe in), 0.00 thrust angle

Many shops don't know how to adjust rear camber properly, unfortunately. The inner point is in a slot on the subframe. Push them to get this stuff accurate (in the green is NOT good enough). This alignment would not result in uneven wear, and is really not track-focused at all, rather a good street alignment.

 

[ChitownStang]

Thanks Brian, The front settings you have above is something I can't achieve correct, so I should leave the front alone?
I will look for a good shop that works on performance cars to get the alignment done properly

 

[BmacIL]

Thanks Brian, The front settings you have above is something I can't achieve correct, so I should leave the front alone?
I will look for a good shop that works on performance cars to get the alignment done properly

The front will probably be very close, but maybe a tad less camber. Make sure the toe is right, and per those specs, though...is also quite important.

 

[Norm Peterson]

What size tires on what width rims?


Norm

 

[ChitownStang]

I have the same spec Tires and wheel setup as the PP except I have Niche Wheels and Nitto NT555 G2's

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