Mustang death wobble?!

[Naschcs]

Hey guys so I have i recently bought stock 2016 mustang GT PP with 30k miles and put on some Steeda sport progressive lowing springs. I recently had a track day at AutoClub speedway and about halfway through the day, the car under hard acceleration would start to get a death-wobble like sway in the rear (not the tires breaking loose lol)! The car still felt pretty planted in smooth in the corners but as soon as i would start to go WOT in the straights or around the roval that wobble would come back and destroy all confidence i had in the car! One shop said nothing was wrong except that the springs i chose are actually trash and not suited for the even the occasional track day??? Any advice or has anyone experienced this before?

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[YoloBathsalts]

Hey guys so I have i recently bought stock 2016 mustang GT PP with 30k miles and put on some Steeda sport progressive lowing springs. I recently had a track day at AutoClub speedway and about halfway through the day, the car under hard acceleration would start to get a death-wobble like sway in the rear (not the tires breaking loose lol)! The car still felt pretty planted in smooth in the corners but as soon as i would start to go WOT in the straights or around the roval that wobble would come back and destroy all confidence i had in the car! One shop said nothing was wrong except that the springs i chose are actually trash and not suited for the even the occasional track day??? Any advice or has anyone experienced this before?

It's hard to analyze from just the brief description. I'm no mechanic but we do have a HPDE section of the forum and those guys know their stuff. I would repost this with some more technical specs on your car in that section and I'm sure they will help you figure it out. My best guess is tires got too hot and turned to jello, or your bumpstops might be too tall? Maybe the previous owner just did springs and didn't match struts to suit.

https://www.mustang6g.com/forums/forums/road-course-track-autocross-hpde.197/

 

[NightmareMoon]

Check rear wheel hubs for play, also let us know what tires and pressures you’re running. Car shouldnt wobble /much/ if things are set up correctly, but some slight wiggle when spinning the rear tires is normal if you haven’t done anything to lock down the rubber in the rear suspension and subframe.

It should self center if your alignment (rear toe) is good and if nothing is loose.

Yeah those specific progressive springs aren’t designed for handling, let alone track use. They’re more for street and show. That said, they shouldn’t cause wobble.

When I had scary wobble accelerating hard, I had a bad wheel bearing and a loose front strut to spindle bolt.

 

[BmacIL]

Check rear wheel hubs for play, also let us know what tires and pressures you’re running. Car shouldnt wobble /much/ if things are set up correctly, but some slight wiggle when spinning the rear tires is normal if you haven’t done anything to lock down the rubber in the rear suspension and subframe.

It should self center if your alignment (rear toe) is good and if nothing is loose.

Yeah those specific progressive springs aren’t designed for handling, let alone track use. They’re more for street and show. That said, they shouldn’t cause wobble.

When I had scary wobble accelerating hard, I had a bad wheel bearing and a loose front strut to spindle bolt.

All this, but also can you post your alignment sheet, @Naschcs ? Did you have the suspension bushings clocked after the suspension install, and before the alignment?

 

[5-PT-OH]

IRS wheel hop?

 

[Naschcs]

Hey guys so I have i recently bought stock 2016 mustang GT PP with 30k miles and put on some Steeda sport progressive lowing springs. I recently had a track day at AutoClub speedway and about halfway through the day, the car under hard acceleration would start to get a death-wobble like sway in the rear (not the tires breaking loose lol)! The car still felt pretty planted in smooth in the corners but as soon as i would start to go WOT in the straights or around the roval that wobble would come back and destroy all confidence i had in the car! One shop said nothing was wrong except that the springs i chose are actually trash and not suited for the even the occasional track day??? Any advice or has anyone experienced this before?

 

[Naschcs]

Hey guys thanks for all the replies!
The car is set up as follows:
MPRB street catback
Ford Power pack 2 (tune, intake, throttle body)
Steeda Sport Progressive Lowering Springs
Front- 255/35/19r s BFG g-force comp 2 on PP wheels (about 31psi)
Rear- 275/35/19rs Michelin pilot sport AS3+ pp Wheels (also about 31 psi)
I plan on getting new tires (275/35/19r Firestone indy 500s all around very soon)

This weekend i plan to add: In hopes to fix the problem
Maximum motor sports caster/camber plates (probably should have been done with install of springs)
Steeda Bump steer kit
These will be followed by an alignment and checking the bearings/ front spindles!
Any other recommendations are highly appreciated

 

[BmacIL]

Hey guys thanks for all the replies!
The car is set up as follows:
MPRB street catback
Ford Power pack 2 (tune, intake, throttle body)
Steeda Sport Progressive Lowering Springs
Front- 255/35/19r s BFG g-force comp 2 on PP wheels (about 31psi)
Rear- 275/35/19rs Michelin pilot sport AS3+ pp Wheels (also about 31 psi)
I plan on getting new tires (275/35/19r Firestone indy 500s all around very soon)

This weekend i plan to add: In hopes to fix the problem
Maximum motor sports caster/camber plates (probably should have been done with install of springs)
Steeda Bump steer kit
These will be followed by an alignment and checking the bearings/ front spindles!
Any other recommendations are highly appreciated

Before buying or installing any more parts, you should get the suspension bushings clocked and get an alignment. Since it's now clearly that you haven't had that done, it seems the likely reason for your woes.

 

[NoVaGT]

Check your wheel bearings.

This is a known issue with 2016 PP cars.

Also, lowering springs without replacing the shocks & struts is pretty useless. The stock springs and struts aren't designed to work with the lower ride-height.

Look at my sig-line, and do all that stuff. You could have skipped the lowering springs.

 

[Ebm]

Never heard of someone having death wobble outside of a solid front axle vehicle like a Jeep lol.

I'm with everyone else:
- Make sure alignment is true
- Check bushings
- Make sure all braking components are tightened, nothing warped
- Check wheel bearings

 

[Cobra Jet]

Check your wheel bearings.

This is a known issue with 2016 PP cars.

Also, lowering springs without replacing the shocks & struts is pretty useless. The stock springs and struts aren't designed to work with the lower ride-height.

Look at my sig-line, and do all that stuff. You could have skipped the lowering springs.

Can’t be stated enough times - DEFINITELY get the rear wheel hubs checked AND make sure the rear hub axle retaining nut is not backing off (another known issue with the S550’s). Torque spec on those nuts should be IIRC, 150ft lbs or better (as some say).

Members have posted numerous threads about having hub failures with in some instances only 3k, 10k+ and 20k+ respectively. Some have even posted they have had the same hub or hubs replaced 2-3x under warranty!

If those rear hubs are bad - OR if the rear axle retaining nut has come loose - you’re going to experience the “snake” or wobbly sensation when putting excessive load on the vehicle either by way of hard acceleration, aggressive lane changes or passes and/or when hitting up twisties.

An alignment (if not done already) is also necsssery - BUT if the rear hubs are bad and they are not addressed you’re throwing alignment $$$ out the door....

 

[DickR]

Hey guys thanks for all the replies!
The car is set up as follows:
MPRB street catback
Ford Power pack 2 (tune, intake, throttle body)
Steeda Sport Progressive Lowering Springs
Front- 255/35/19r s BFG g-force comp 2 on PP wheels (about 31psi)
Rear- 275/35/19rs Michelin pilot sport AS3+ pp Wheels (also about 31 psi)
I plan on getting new tires (275/35/19r Firestone indy 500s all around very soon)

This weekend i plan to add: In hopes to fix the problem
Maximum motor sports caster/camber plates (probably should have been done with install of springs)
Steeda Bump steer kit
These will be followed by an alignment and checking the bearings/ front spindles!
Any other recommendations are highly appreciated

Are you saying the car was lowered but you didn't get it aligned afterwards by anyone let alone an alignment shop/tech that knows S550's?

 

[Ecoboosted]

Can’t be stated enough times - DEFINITELY get the rear wheel hubs checked AND make sure the rear hub axle retaining nut is not backing off (another known issue with the S550’s). Torque spec on those nuts should be IIRC, 150ft lbs or better (as some say).

Members have posted numerous threads about having hub failures with in some instances only 3k, 10k+ and 20k+ respectively. Some have even posted they have had the same hub or hubs replaced 2-3x under warranty!

If those rear hubs are bad - OR if the rear axle retaining nut has come loose - you’re going to experience the “snake” or wobbly sensation when putting excessive load on the vehicle either by way of hard acceleration, aggressive lane changes or passes and/or when hitting up twisties.

An alignment (if not done already) is also necsssery - BUT if the rear hubs are bad and they are not addressed you’re throwing alignment $$$ out the door....

Yep happened to me when i installed the Track Pack Suspension. I didn’t torque the right rear axle nut properly which resulted in a loose rear end when accelerating hard and getting the rear to go from side to side. Ended up ruining the right rear bearings.

 

[Naschcs]

The car was aligned after the spring install, I am just on vacation and don’t have access to the alignment sheet at the moment. Taking the car in this weekend when I am back to have all things stated above checked and for a realignment. Realizing now the lowering springs were maybe not the long term move for me and should have just saved up for a coil overs kit.

 

[Bluemustang]

The car was aligned after the spring install, I am just on vacation and don’t have access to the alignment sheet at the moment. Taking the car in this weekend when I am back to have all things stated above checked and for a realignment. Realizing now the lowering springs were maybe not the long term move for me and should have just saved up for a coil overs kit.

You don't need coilovers. You're just using soft springs designed more for daily driving not performance driving. Check the hubs and alignment as said before.

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