Improved suspension without lowering?

[pstoppani]

I have a non-PP Mustang that is not quite where I want it. I like the approach of keeping the stock height (I really don't want to lower the car any) and see wisdom in starting with shocks and struts. My question is, once I get the struts and shocks dialed in, where do you go from here? There are multiple sway bar options; however, I don't think it is wise to put in stiffer sway bars without looking at the spring rates. Usually its a package deal, going with a stiffer sway bar with "softer" springs I think will cause other issues (forgot the term but its when you get one side with rough conditions and it translates it to the opposite side).

Again, I'm not wanting to lower the car at all, think it sits good where its at now. I could live with a slight drop (less than an inch) but there are no offerings out there that I have seen that stiffen up the springs and keep the drop to a minimum (BMR min drop springs seem to only exist for the front, nothing for the back for us non PP guys).

Your thinking is dead on! Best approach is a package. But, starting with dampers, then springs, then sways (which really should be upgraded only to match the package and to allow for adjustment; not to control roll on their own) is a fine approach (if you can ignore the labor costs).

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[BMR Tech]

OP, here is my suggestion.

1: One adjustable bar. I prefer the front.
2: Dampers. FRPP Track, Konis, or the Bilsteins if they ever come out.
3: Remove all of the deflection within the IRS and the sway bar system, to take advantage of the parts you have.

People overlook how much performance is lost within their suspension, from deflection. For example, sway bars. You can gain 10+% in bar rate by removing the deflection in the bar from the rubber bushings.

Good luck!

 

[Performance nut]

Your thinking is dead on! Best approach is a package. But, starting with dampers, then springs, then sways (which really should be upgraded only to match the package and to allow for adjustment; not to control roll on their own) is a fine approach (if you can ignore the labor costs).

I don't mind suspension work. Rebuilt an entire suspension on a Corvette and loved how it turned out. Looking to repeat that here.

OP, here is my suggestion.

1: One adjustable bar. I prefer the front.
2: Dampers. FRPP Track, Konis, or the Bilsteins if they ever come out.
3: Remove all of the deflection within the IRS and the sway bar system, to take advantage of the parts you have.

People overlook how much performance is lost within their suspension, from deflection. For example, sway bars. You can gain 10+% in bar rate by removing the deflection in the bar from the rubber bushings.

Good luck!

Couldn't agree more, thank you for putting that out.

To point #3, I like that there are multiple frame stiffening solutions out there though the point with the rubber bushings, I would ask if you mean going to poly or solid connections. I personally don't like putting poly or going to solid links in a street car (though done so in few places). Not only is it uncomfortable and sometimes noisy but I've seen control arms ripped from the frame because the connection gave more than the suspension.

Could you elaborate on specifics? I appreciate it

 

[BmacIL]

I don't mind suspension work. Rebuilt an entire suspension on a Corvette and loved how it turned out. Looking to repeat that here.



Couldn't agree more, thank you for putting that out.

To point #3, I like that there are multiple frame stiffening solutions out there though the point with the rubber bushings, I would ask if you mean going to poly or solid connections. I personally don't like putting poly or going to solid links in a street car (though done so in few places). Not only is it uncomfortable and sometimes noisy but I've seen control arms ripped from the frame because the connection gave more than the suspension.

Could you elaborate on specifics? I appreciate it

Pretty sure he's referring to the CB005 cradle lockout kit, as well as Toe Links, Vertical Links and Control Arm Bearing. If you get the bearing/bearing vertical links, none of those have a negative impact on NVH, just improvements in control.

 

[Norm Peterson]

Even with an IRS car, I think I'd want to be able to use rear sta-bar adjustments for making the final tweaks to suit the balance I'm looking for. Typically, the front bar is responsible for the majority of the roll stiffness coming from the bars. The rear bar mainly adjusts the front to rear roll stiffness balance without affecting the amount of roll/g enough to matter.


Norm

 

[EricSMG]

New guy here with '17 base GT/PP, total suspension freak. I'm very experienced with modifying BMW suspensions and so I'm stepping into this world carefully. As I've learned with the Bimmers, there is, virtually, no free lunch. In other words, almost all 'mods' have a downside. I too, want a better 'driving' road car without going lower, or, very minimally lower.

The biggest issue, BY FAR, with these cars is their crappy OE shock valving. The front PP struts are ridiculously too soft in low/mid comp AND rebound so the front of the car literally floats. It also dips under initial braking and rises dramatically under power. This makes the car, well, feel very imprecise relative to the other car in my garage.

The rear PP shocks have too much mid/high compression and not enough rebound. The rear of the car pogos around, very harsh riding and yet somehow, still, not very controlled. Ford really screwed these up. In fact, I've never seen a dyno curve like this, it's literally upside down in terms of bump/rebound ratio.

The second biggest issue that I can see thus far in my first week/200 miles are the mickey mouse diff bushings. Really? These things are WAY too soft. As such, they allow the diff to 'rock' in the cradle something fierce, virtually eliminating any sense of connection between the throttle and the rear wheels. The driveline has a very lazy feel and, accelerating smoothly out of a corner is not possible.

So, with that, I will be addressing first:

1. Dampers
2. Diff bushings

** Side note - I'm considering the BMR minimum drop fronts (7/8") and perf. rears (1/2") springs but I'm highly skeptical, based on my years of tweaking other cars, that while their rates are similar (but linear) to stock PP rates AND their drop minimal, that they won't negatively affect ride quality. I'm open to the idea that I could be wrong, though.

 

[BmacIL]

I would try isolating the IRS cradle before diff bushings. A lot of what you're feeling driving the car is the subframe (cradle) moving around. BMR CB005 will take care of that, as will the Steeda package of the bushing support system and subframe braces combined.

 

[EricSMG]

I would try isolating the IRS cradle before diff bushings. A lot of what you're feeling driving the car is the subframe (cradle) moving around. BMR CB005 will take care of that, as will the Steeda package of the bushing support system and subframe braces combined.

Yes, it could very well be. But looking at the various videos showing 'on/off' throttle and how much the actual diff rocks in the cradle..... this seems to align with what I'm feeling. The cradle itself doesn't seem to move much under pure throttle inputs, excluding drag launches, which I have zero concern with.

The diff bushings are cheap, non-invasive and cake to install so it seems like a low risk 'upgrade'. My concern is, obviously, diff wine but again, cheap/easy/easy to UN-do so why not try.

The Steeda braces seem neat but I imagine them flexing a lot, as the cradle moves, without the additional cradle inserts. Additionally, its seems that the single outboard frame tie/bolt would literally be tasked with handling 100% of lateral (cornering) load. Hmmmm.

 

[BmacIL]

Yes, it could very well be. But looking at the various videos showing 'on/off' throttle and how much the actual diff rocks in the cradle..... this seems to align with what I'm feeling. The cradle itself doesn't seem to move much under pure throttle inputs, excluding drag launches, which I have zero concern with.

The diff bushings are cheap, non-invasive and cake to install so it seems like a low risk 'upgrade'. My concern is, obviously, diff wine but again, cheap/easy/easy to UN-do so why not try.

The Steeda braces seem neat but I imagine them flexing a lot, as the cradle moves, without the additional cradle inserts. Additionally, its seems that the single outboard frame tie/bolt would literally be tasked with handling 100% of lateral (cornering) load. Hmmmm.

Go to 1:29 to see how much the cradle moves under power application (not just launch):

 

[EricSMG]

Good video. It sure does move a lot, doesn't it. I guess it's a combo of both I'm feeling.

That said, your suggestion is well noted as it will not only reduce this 'rocking' I'm feeling but also increase lateral stability, so two birds, if you will.

 

[BmacIL]

Good video. It sure does move a lot, doesn't it. I guess it's a combo of both I'm feeling.

That said, your suggestion is well noted as it will not only reduce this 'rocking' I'm feeling but also increase lateral stability, so two birds, if you will.

The ride is improved too. The dampers can't properly control sprung mass that's moving around like that, thus basically acting like unsprung mass. Think about this: the diff movements are exaggerated by the cradle movements because the diff is mounted within it. Yes, the bushings for the diff are soft, but you'll only really notice them being a problem under hard launch once the cradle is locked down.

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