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Car swaying at high speeds

Shdwrlmstang

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Hello everyone hope you all had a wonderful New Years. My issue if someone can please assist is that at high speeds my car is now swaying way to much, it feels completely unsafe and abnormal. This is after installing an h pipe, intake, throttle body, tune, Ford performance lowering springs, and Steeda stop the hop kit on a 19 mustang gt PP. The tires are factory Michelin pilot 4s from the factory( Bought nitto nt555 275 front and 305 rear. Just waiting for delivery) also purchased front and rear eibach sway bars. Iā€™m hoping those two installs should fix my issue but If not, is there anything you guys can recommend to look into. Whatever I listed is exactly whatā€™s been installed nothing else. Iā€™m thinking shocks struts etc but would love feedback from you pros. I looked online already but it didnā€™t hit the spot for me. I would appreciate any feedback thanks
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S7N

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What speeds exactly and did you do an alignment after lowering the car? Check tire pressure? and might be a dumb question but you didn't install the springs upside down did you?
 
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Shdwrlmstang

Shdwrlmstang

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Lol Definitely not upside down. Yes did an alignment, tire pressure is 35 front 32 rear, and sorry high speeds meaning around 110-130 it begins and I always let off because you can feel it
What speeds exactly and did you do an alignment after lowering the car? Check tire pressure? and might be a dumb question but you didn't install the springs upside down did you?
 

S7N

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Lol Definitely not upside down. Yes did an alignment, tire pressure is 35 front 32 rear, and sorry high speeds meaning around 110-130 it begins and I always let off because you can feel it
Since you have the ford performance lowering springs I'd go ahead and get the ford performance track handling pack shocks and struts also. I'm pretty sure that will eliminate most of that floaty drifting feeling you get . Sway bars alone won't fix that feeling. I had a similar issue and once I put the steeda pro action shocks and struts on the car it was night and day difference. I can do 130mph and feel like I'm going 55mph big difference.
 
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Shdwrlmstang

Shdwrlmstang

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Since you have the ford performance lowering springs I'd go ahead and get the ford performance track handling pack shocks and struts also. I'm pretty sure that will eliminate most of that floaty drifting feeling you get . Sway bars alone won't fix that feeling. I had a similar issue and once I put the steeda pro action shocks and struts on the car it was night and day difference. I can do 130mph and feel like I'm going 55mph big difference.
Yes sounds about right thatā€™s exactly what I was thinking Iā€™ll add shocks struts to the sway bars and new tires and that should most definitely fix my issue thanks I appreciate it
 

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Yes sounds about right thatā€™s exactly what I was thinking Iā€™ll add shocks struts to the sway bars and new tires and that should most definitely fix my issue thanks I appreciate it
No problem buddy. This is the list of stuff I've done to my car as a reference.

555 4450 Steeda S550 Subframe Alignment & Support
555 8210 Steeda Sport Springs Progressive GT/V6 20
555 1015 Steeda Mustang Front Sway Bar 2015-2018
555 1016 Steeda Mustang Rear Sway Bar 2015-2018
555 4120 Steeda Adjustable Rear Toe Link S550
161 M 5A460 M FRPP Knuckle to Toe Link Bearing Assembly
555 4445 Steeda Adjutable Bump Stop Kit Front & Rear
555 8150 Steeda Pro-Action Non-Adj. Shocks and Struts
555 4437 Steeda IRS Subframe Bushing Support System
 
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Shdwrlmstang

Shdwrlmstang

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You might want to even these out. Do not see the need for the fronts being that high. Must be high 30's when they are hot, right?
Iā€™m in New York itā€™s like 30-40 degrees these days thatā€™s why i set like that. What tire pressure do you run when itā€™s nice and warm out? Also I barely drive this car in the cold so Iā€™m not worried about the TP
 

Bikeman315

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Iā€™m in New York itā€™s like 30-40 degrees these days thatā€™s why i set like that. What tire pressure do you run when itā€™s nice and warm out? Also I barely drive this car in the cold so Iā€™m not worried about the TP
I normally run 33 all around. Iā€™ll back it down one or two when it gets really hot out. Always run the same all around.
 

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Check this thread which is similar:
https://www.mustang6g.com/forums/threads/car-swaying-side-to-side-at-high-speeds.115937/

It may have some info for your swaying issues.


ā€”
Also, you should always be running equal tire pressure all around on a street car. Tire pressure should always be taken when the tires are stone cold. Door VCL, IIRC is 32 or 33 psi at all 4 corners when cold. When the tires heat up from driving that cold psi will also rise, slightly. You may see 35-36psi when warm (even on cold days).

Iā€™m right next to you in NJ, same exterior temps, running equal tire psi at all four corners. If youā€™re running unequal psi, itā€™s going to cause performance issues at higher speeds, especially maneuvering from lane changes, curves on/off ramps as the body of the car rolls/leans left or right from weight transitioning.
 

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Avispa

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You will have to run lower pressure in the back once you put those 305s on. Had staggered tires/wheels on the Terminator, 275/40 front and 315/35 rear, and needed to run 32 front and 26 rear to keep the tire wear on the rear even across the tread surface.
 

brl0301

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I went through the exact same thing after lowering my car. After dealing with it for a few months, I loosened everything in the rear end and retorqued everything to spec. That did the trick and its been good ever since then
 

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How are the inner edges of your tires wearing in the front? Even with a factory spec alignment the inside edges of the front tires will wear quicker and 100% cause a floaty/jerking steering feeling.

My suggestion is either that or as mentioned, struts need to be upgraded to handle the new springs better.

Anothe thing - did you get a copy if the alignment specs? I have read several times on here that any time youā€™re dropping the IRS cradle there can be significant alignment adjustments required to bring it back to spec.
 

w3rkn

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You will have to run lower pressure in the back once you put those 305s on. Had staggered tires/wheels on the Terminator, 275/40 front and 315/35 rear, and needed to run 32 front and 26 rear to keep the tire wear on the rear even across the tread surface.
Then what would be the point of putting wider tires on the rear, in the first place..?
 

Avispa

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To have enough traction so that 500+ lbs of torque at the wheels from 2000 rpm on up won't smoke the back tires. The factory 275s just didn't cut it after putting on the Whipple.

The lower pressure in the rear is a matter of having a larger tread area in contact with the road. More area equals lower pressure to get the same contact pattern as in the front.
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