S550 mustang floating at high speeds

[Peter15051]

Hey guys, I know it is very common for mustangs to have a floating feeling or feel like a slow side to side motion at high speeds—what I want to know is from those who have eliminated this issue, what did you do? I’m on ford lowering springs 1” drop all around, otherwise suspension is stock. I have aftermarket wheels and tires. Michelin pilot sport 4s 255 up front and 295 in the rear. Wheels are 19x8.5 front and 19x9.5 in the rear drag dr 37.
I’ve seen some guys claim tightening a single bolt fixed this, may be true but seems very simplistic. I’m thinking to do a coil over kit for a fix. Your thoughts and experience.

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[Crew4991]

How fast we talking?
I think most mustangs will have a side to side motion when doing 140mph down the interstate with flashing lights behind em.

 

[NightmareMoon]

What do you mean by floating feeling? Are we talking up and down motions or something else?

Was the car a base GT originally before the springs? Most importantly, how many miles on the shocks, and are they stock?

 

[Peter15051]

Side to side like a fish tail. Only about 80mph it starts. By 100 it’s scary

 

[ORRadtech]

Side to side like a fish tail. Only about 80mph it starts. By 100 it’s scary

Well, that's not right.
I don't have a solution for you but my bone stock EB convertible is rock solid at 110...

 

[Peter15051]

I just spoke to the accessory guy at the dealer. He said he will do some research but he suggested starting with track pack away bars.

 

[KingKona]

I just spoke to the accessory guy at the dealer. He said he will do some research but he suggested starting with track pack away bars.

Your guy has no idea what he's talking about.

You have a wealth of information already presented to you in the other thread. Why are you ignoring it?

 

[NTXChris]

Up/down motions can be attributed to springs/shocks. Side-to-side is a different animal all together. Did you get your car aligned after lowering it? If not, that's probably the source if your issues.

If aligned, I would start looking at wheel bearings. If there is any play in the wheel while the car is jacked up, you need to replace the bearings. Several on the site have mentioned strange handling issues when wheel bearings begin to fail.

Edit: Your rear tires may be a little too wide for the wheel. I'm not sure about drag radials, but typically the max section width for a 9.5 inch wide wheel is 285.

 

[HKusp]

I have been 140 on the highway with my non-PP car on stock springs and struts. There is zero, side to side "floating". You have a MAJOR issue going on if it's doing it at 80mph.

 

[SBR70.3]

Check and clock all of the bushings on the rear of the car. I had this issue at one point. I replaced my toe links and clocked the bushings. Problem solved.


Can not recommend this enough.....clock the bushings. There is a priceless sticky thread on this.

 

[Peter15051]

I’ll consider these things. However I’m getting different solutions and many of them seem possible. My car only has 3000 miles on it so whatever it is they’ll fix it. I may reach out to a performance shop for their ideas as well. I appreciate all the suggestions and directions to try.

 

[NeverSatisfied]

Instability at 80 is not normal. 140+ with no aero and they start to get a little “light” feeling.

 

[Garfy]

I have been 140 on the highway with my non-PP car on stock springs and struts. There is zero, side to side "floating". You have a MAJOR issue going on if it's doing it at 80mph.

I have to agree. My bone stock base GT has gone over 100 mph with no issues, totally solid and stable ride. Haven't pushed to 120+ but if he's got an issue at merely 80 mph, something's awfully amiss and potentially dangerous.

 

[Peter15051]

Appreciate your input about what speeds you can hit without losing any stability. This gives me a good benchmark to consider.

 

[NightmareMoon]

Very odd. Car should not fishtail or wobble side to side at any speed. Definitely not 80 mph cruising. If you're accelerating hard at 80 and its fishtailing, that's another issue. You have a blower and if this is under power when its doing it, you could be slipping tires. The way to solve wobble under power is to get much better tires and/or secure the rear subframe and remove rubber from the rear control arms by replacing bushings with bearings. The car will wobble a bit when its accelerating so hard you're spinning tires unless you address the amount of rubber in the rear suspension. For N/A stock powered cars, this is usually only a minor issue in 1st and 2nd gear.

If this is at 80mph cruising then the first stop should probably be an alignment rack to check the toe settings and make sure you have the right amount of toe in at the rear. While you're on the alignment rack, have them reclock the bushings in case that wasn't done when the springs were installed. Report back after the alignment.

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