Performance Pack suspension bouncy?

Hase said:

I have a question on the 15 performance pack suspension.
In driving mine, I have noticed that while driving on the freeway the car almost seems slightly bouncy. (or should I say, I am bouncing in my seat) This isn’t because of potholes or bumps but more so the connection points in the slabs of the road.
When driving over potholes / bumps, the car is firm but not uncomfortable. It does not seem bouncy at this point.



What causes this bouncy feeling?

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I have a regular GT and mine is bouncy as well. (I have the 20's if that makes a difference) There's no way I'm putting lowering springs on the car so hopefully someone comes out with some better dampers soon. I'm afraid anything the aftermarket offers is going to stiffer (for better cornering) and not smoother.

Also, I test drove a regular GT with 50th AP and it was bouncy as well. I'm thinking some people aren't understanding what bouncy means to us.

Stang Nut said:

I have a regular GT and mine is bouncy as well. (I have the 20's if that makes a difference) There's no way I'm putting lowering springs on the car so hopefully someone comes out with some better dampers soon. I'm afraid anything the aftermarket offers is going to stiffer (for better cornering) and not smoother.

Also, I test drove a regular GT with 50th AP and it was bouncy as well. I'm thinking some people aren't understanding what bouncy means to us.

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Dampers aren't always going to be stiffer, and stiffer isn't always better. Dampers that better control the spring rate and body motions will absolutely increase ride quality.

Chameleon said:

Springs will help with this.

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Doing springs but not shocks & struts may help a "bounce" problem (by cutting down the amount of motion under some situations), but this will come at some cost in increased "floatiness" (where the stiffer springs are overpowering the OE dampers, something that will get worse as the miles are run up).


Norm

i noticed this bounce only after i started reviewing my dash cam videos. i noticed that im bouncing in my seat while on the highway.

i chalked it up to having a "sporty suspension", not because the car doesn't have enough dampening.

you can see me bouncing around here

When there isn't enough damping, the spring stiffness will cause the suspension to 'overshoot' further upward beyond its static equilibrium position, after which it will have to drop back down. A little overshoot isn't particularly noticeable, but as the springs get stiffer and the dampers don't it will show up.

Under the topic of "damped vibrations", this gets into something called "percent critical damping".


FWIW, I can't really tell from the video whether the bounce is purely vertical 'heave' or if there's some nose up/down - tail down/up 'pitch' motion as well. Pitch motion would suggest that the front and rear spring stiffnesses could be better chosen, at least for that road at that speed with that amount of front and rear damping. See 'flat ride' topics under vehicle dynamics.


Norm

I have a GTPP and I do notice the bounciness at times. I will have to pay more attention when and where it is happening.

I am also getting a full compliment of Steeda suspension parts installed pretty soon so I will be able to compare stock PP vs. aftermarket.

Todd15Fastback said:

I have a GTPP and I do notice the bounciness at times. I will have to pay more attention when and where it is happening.

I am also getting a full compliment of Steeda suspension parts installed pretty soon so I will be able to compare stock PP vs. aftermarket.

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I would love to hear how it turns out and a comparison, Thanks!

Hase said:

I would love to hear how it turns out and a comparison, Thanks!

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I will for sure! You can click the build thread link in my sig and see all the Steeda parts I am getting installed. Just waiting for the springs to arrive and I will get my appointment setup ASAP.

we won't be able to get really aggressive spring rates until someone releases a damper with valving that will control those springs accurately... which is why I brought up (JRI Shocks in another thread) if the 2014 units would fit on a 2015 chassis. they look very similar even though the rear of our 6th gens is independent.

Asharus said:

i noticed this bounce only after i started reviewing my dash cam videos. i noticed that im bouncing in my seat while on the highway.

i chalked it up to having a "sporty suspension", not because the car doesn't have enough dampening.

you can see me bouncing around here

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How do you have the camera mounted? I was watching the video and noticed the car seems stable but could see you bounce in the seat a little.

it's a headrest mount and a mobius dash cam

So here is an interesting update: Had to pick up 3 boxes of paper at lunch - Roughly 160lbs in the trunk - All of the bounciness was gone. So does this point to too firm a rear spring / shocks can't handle the first bit of travel on Michigan roads?

Hase said:

So here is an interesting update: Had to pick up 3 boxes of paper at lunch - Roughly 160lbs in the trunk - All of the bounciness was gone. So does this point to too firm a rear spring / shocks can't handle the first bit of travel on Michigan roads?

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Interesting! My EBM is my daily driver and while I think it's a great car, the ride stinks. I'm not expecting a Cadillac-cushy ride but the bounciness is hard to deal with.

Maybe a couple of 80# bags of Sakrete in the spare-tire well is all that's needed! That's a heckuva lot cheaper and easier than replacement springs/shocks/struts. I'm only semi-kidding......

perhaps the road you were driving on was flatter than usual.

Asharus said:

perhaps the road you were driving on was flatter than usual.

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Same road...