Performance Pack suspension bouncy?

[BmacIL]

At speeds of <60 mph, I did not find the PP GT to be bouncy. I believe it is mostly at higher speeds which makes the same size road input a higher impulse (faster input but same displacement). This again points to a front /rear match issue as Norm correctly stated. The time between the bump hitting the front wheels to the back wheels decreases and in order for the chassis to settle and not overshoot (bounce), the front to rear ride frequencies have to be matched. From my race car engineering days, I remember the rear ride frequency needed to be 1.1-1.3 times the front, depending on wheelbase, weight distribution and desired control speed.

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[Rv-Junke]

I rather doubt that the PP shocks and/or struts are position-sensitive (damping that varies with ride height as well as with its piston speed - think "suspension speed", relatively slow in roll, squat, and brake dive but much faster when you hit a sharp bump).

What adding weight at just the rear does is slow down the rear suspension's natural frequency, and having the front and rear suspension frequencies in the proper relationship to each other does affect ride quality. Poorly chosen, it might feel like you're riding in an old pickup truck with nothing in the bed, were you get a lot of nose-up/tail-down and vice versa motion of the truck as a whole and front-to-back head-toss for you in particular.

If only the rear shocks aren't up to snuff you won't get as much head toss, but the rear suspension may feel like it'll never stop moving even though the front feels 'settled'. Anybody who has ever changed only the front shocks on a car knows how this feels.

This could be a little of both . . .


Norm

Thanks Norm...So in essence the suspension as a whole maybe off.

 

[leszek]

Has anyone tried the Viking rear shocks with a soft compression and hard rebound settings? I bet that would fix the bounciness quickly.

 

[Hack]

If weight in the rear helps to reduce the problem you are having, then you want softer and less sporty suspension. I can see where coming from more cushy cars the Mustang suspension setup could be irritating especially if you don't do performance driving. It's less relaxing riding in a car with sportier and stiffer suspension.

To me the car is extremely soft and compliant, but I have a base (non PP) GT, and I'm coming from the SRA 2011 GT with the Brembos/track pack and stiffer suspension. That car was uncomfortable some times, especially when our roads got rough in the middle of winter. -20 degree weather really opens up the expansion joints.

It's like when I drive around in my F250 plow truck - you feel every bump in the road. But if I have 500-600 lbs of weight in the back it rides great. Nice and cushy. That's because the springs are stiff in order to be able to haul large loads. For the Mustang it's the same, but the springs are somewhat stiff in order to control the body well over discontinuities in the road. It's funny because to me the springs on my 2015 GT seem really soft to me, but it all depends on what you are used to.

 

[Norm Peterson]

If weight in the rear helps to reduce the problem you are having, then you want softer and less sporty suspension.

It's more complicated than "softer and less sporty". Especially when you try to optimize the compromises among several somewhat contradictory requirements and aren't going to discard any of the 'sport'. Pitch motion and flat ride considerations are but one aspect.


Norm

 

[Rv-Junke]

If weight in the rear helps to reduce the problem you are having, then you want softer and less sporty suspension. I can see where coming from more cushy cars the Mustang suspension setup could be irritating especially if you don't do performance driving. It's less relaxing riding in a car with sportier and stiffer suspension.

To me the car is extremely soft and compliant, but I have a base (non PP) GT, and I'm coming from the SRA 2011 GT with the Brembos/track pack and stiffer suspension. That car was uncomfortable some times, especially when our roads got rough in the middle of winter. -20 degree weather really opens up the expansion joints.

It's like when I drive around in my F250 plow truck - you feel every bump in the road. But if I have 500-600 lbs of weight in the back it rides great. Nice and cushy. That's because the springs are stiff in order to be able to haul large loads. For the Mustang it's the same, but the springs are somewhat stiff in order to control the body well over discontinuities in the road. It's funny because to me the springs on my 2015 GT seem really soft to me, but it all depends on what you are used to.

Just to level set...

My DD is a 2012 Raptor with Fox 3.0, not exactly Cushy
My Sunny day car is a 2014 GT500, not exactly Cushy
My Family car is a 2011 Mercedes S550, DEFINITLY Cushy

So just on the cars I am currently driving I know Stiff/Sporty, Cushy/Plush, and BOUNCY which is what the PP in the 2015 Mustang is...This is 100% problem with compatibility with the early compression of the springs to dampeners (shocks).

 

[dhardison]

Since I haven't had the time to install my Steeda progressive springs I thought I'd try a quick little test. I measured from the ground to the topmost rear wheel opening with no weight in the trunk. Then I put 160# in the trunk (barbell weights, 2 45# & 2 35#) and measured again.

Interestingly it was only a 3/8" drop, but MAN what a HUGE difference in the ride quality! The bounciness is gone and the car now rides like it should, well except for those pesky weights sliding around in the trunk.....

 

[Hase]

Just to level set...

My DD is a 2012 Raptor with Fox 3.0, not exactly Cushy
My Sunny day car is a 2014 GT500, not exactly Cushy
My Family car is a 2011 Mercedes S550, DEFINITLY Cushy

So just on the cars I am currently driving I know Stiff/Sporty, Cushy/Plush, and BOUNCY which is what the PP in the 2015 Mustang is...This is 100% problem with compatibility with the early compression of the springs to dampeners (shocks).

So if you really think this is the case, I am wondering if the adjustable warrior shocks could be a potential solution. http://www.mustang6g.com/forums/showthread.php?t=23530

 

[Falconeddie]

Not true my friend. I have a 2006 Mustang GT premium and it rides way better than my 2015 GT premium. Ford has some work to do on its new independent suspension tuning.

 

[Rags828]

When I think of the word "bouncy" a secondary motion is implied -- I hope that's not what the consensus is here -- I didn't feel any of that on my test drive. I felt the bumps and joints in the road surface, but I never felt each one more than once, if that makes sense...

Yes, I've had quite the time of trying to figure out how to describe my ride quality.

I'm thinking floaty is more of what I'm talking about. It's like when I go over a bump (not even a harsh one), the rebound or extension of the shocks/springs travels way too much. And then the rates catch up and the bump bring it back down. All of which feels like it's going to throw me out of my seat.

I'm after a more planted feel and would be very happy with a firmer setup. I'm going to look at some Steeda and FR components to hopefully resolve.

 

[hiccup]

Freshly paved roads seem to be the only chance I get at a very smooth ride. I've always felt that the bouncing was caused by the rear suspension shocks not being compatible with the factory pp rear springs ... Hope my koni str.t's correct this should I ever get the chance to install them.

 

[VinnAY]

I have just one small stretch of road that has some aspect to it that I get the bounce over the rear end enough to be annoying, no where else really that I ever notice but the bounce is jarring enough to be noticeable and irritating. I'm running Steeda: diff bushings, IRS supports, IRS braces, and sway bar.

 

[Norm Peterson]

Sounds like insufficient rear shock damping or possibly a mis-match between bump damping and rebound damping. I'm assuming that this bouncing isn't a harsh thing, just a refusal to settle down.


Norm

 

[fcarpio]

Springs will help with this.

I got the Eibach SportLines and made my suspension worse, made it feel like the car was floating. Not nice at all. Then I got the Steeda shocks and struts, problem solved. The car has a slightly stiffer suspension but it feels very planted.

 

[BmacIL]

Sounds like insufficient rear shock damping or possibly a mis-match between bump damping and rebound damping. I'm assuming that this bouncing isn't a harsh thing, just a refusal to settle down.


Norm

It's this plus a poor shock mount design (at body and control arm) that induces bind and added sliding friction in the shock, as well as stiction to a degree.

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