Bouncing '19 Bullitt

[K0094]

I have a 2019 Bullitt with about 15k on the odometer and the car is equipped with magneride. The magneride rear shocks were leaking and replaced about 3k miles ago.

The car bounces driving down the highway at 70-80mph, even in sport or track mode where the shocks have noticeably firmed up after changing the drive mode. When having a conversation on the highway, my words are not clear from the car bouncing. My voice/words sound as if i was hitting my chest while trying to talk. My first thought would be the shocks are bad, but both rears were just replaced and shocks definitely get firm when the drive mode changes. This is my daily driver.

I recently modified the IRS which includes:
- replaced the LCA front bushing with a spherical bearing
- replaced the knuckle to toe bushing with the Ford Per bearing
- BMR double adjustable toe rods
- BMR vertical links, spherical/delrin
- BMR lockout lvl 2
- BMR IRS/subframe support brace
- All bolts torqued to spec with the suspension loaded as it would sit (clocked).

The springs are stock on the rear. Front suspension is unmodified. It didn't bounce prior to modifying the IRS.

Has this happened to anyone else after modifying the IRS?
Suggestions to getting rid of the bounce?

Thanks for any feedback.

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[KilgoreLSU]

How do you know it's the rear that's bouncing and not the front? When the rears failed, did it bounce the same way?

 

[Swtbabybilly]

How are the front struts? The rear is now very stiff with brand new shocks and the front is stock with struts that are 6 or 7 years old now. If the front struts are bad or going bad and the rear of the car is now very stiff this could definitely cause a bounce or floating feeling when driving at highway speeds, best of luck man

 

[K0094]

How do you know it's the rear that's bouncing and not the front? When the rears failed, did it bounce the same way?

Thanks for the reply.

It didn't bounce until I modified the IRS. That is why i believe the bounce comes from the rear. The rear shocks were replaced under an extended Ford warranty when i found them leaking. There were about 3k miles put on the car with the new magneride rear shocks prior to the IRS modifications. It wasn't bouncing in those 3k miles (it wasn't riding any differently then when the shocks were leaking).

After discovering the bounce, i loosened the bolts and re-torqued them again with the suspension loaded. That was the second time i clocked the suspension bolts.

I was almost wondering if the magneride system needs to be reset or something. I don't know if it has a learning ability or not.

 

[K0094]

How are the front struts? The rear is now very stiff with brand new shocks and the front is stock with struts that are 6 or 7 years old now. If the front struts are bad or going bad and the rear of the car is now very stiff this could definitely cause a bounce or floating feeling when driving at highway speeds, best of luck man

Thanks for the reply.

I didn't see any leaks from the front struts. The front seems to be ok. I had one of my local Fords do an alignment which made the car darty and the bump steer even worse. They moved the toe in on the front. I got another alignment at a dirfferent shop and had them move the front toe about 0.01 degree out which made the steering float a bit. The S550 seems to be really sensitive to alignment.

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