Help me please: I have suspension mods but still feels meh

[SDAMike]

Hi everyone, I have been meaning to post this for months. I was hoping to get some help on my suspension set up. I have a number of mods, but to be totally honest I do not like the way the car rides or handles. I dont have a lot of confidence in how the car handles and feel like the ass is unpredictable at best. It takes bumps fairly stiff and can be quite a bumpy ride over the right roads to the point where I avoid taking this one stretch of highway that has many divisions in the pavement as it is a really rough ride that is visibly moving me in my seat up and down up and down lol.

I feel like the front end is...not sure how to explain...loose? Definitely not solid or tied together.

I took a very odd and mismatched approach to my parts buying when I first got the car so I probably created my own problems here.

For the wheels and tires I wanted to get as light as possible and still be able to afford them so thats how I ended up with the Dekagrams that come in at 19.8 lb each and the Conti Tires. (I actually dropped 10 lbs a corner over my black package wheels and tires)

So, heres what the car has:
Its a 2019 GT premium - non performance pack
19x9.5 Konig Flowformed Dekagram wheels
285/40 Continental Extreme Contact tires --- SORRY THEY ARE 285/35's MY BAD!!!
BMR adjustable F+R sway bars (both on the softest setting)
Accelatec (CJ's) Springs
RTR (koni) Adjustable Shocks and Struts
Steeda rear shock mounts
Steeda Camber Plates
BMR CB005
Alignment "close" to BMR's street specs ..... getting a good alignment around here was next to impossible and turned into a multi week ordeal

I think thats its for suspension parts.

Maybe worth noting: I have tried messing with the shock and strut valving a few times. Full soft rode really nice but once I put on the new larger wheels and tires, the ass end felt like a mushy wet noodle, so I turned the shocks up and that helped address that. But the ride quality def. took a hit.

I am not looking to road race the car but I love taking my corners fast and at some point may go autocross with my bud. I also do not expect a perfect ride but I also dont want to bouncing up and down in my seat looking like I am riding in a horse buggy on a rocky dirt road in the 1800's.

I feel like I am missing some vital parts here but I am not sure what at this point. Is there any bracing, or anything from a PP mustang I should have? Is sway bar preloading a real problem with being lowered? Should I get some adjustable end links? Do I need to tie the front end together better...I do not have a strut tower brace, and was thinking of steedas 2 pt G trac brace.
I would REALLY rather not tear everything apart and start over, I would rather add parts. BUT, if something here is really wrong or needs to be changed I am def. willing to do what I need to. Also not trying to spend a shit ton of money either.

I had a GTI autobahn before the Mustang and that car was simply confidence inspiring, even stock. I know the Mustang wont feel like that car, but I cant imagine that this is as good as it gets.

Sorry for the long post but I wanted to be detailed. Appreciate any help!!!

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[NightmareMoon]

What feels wrong?

The only thing that sticks out is your springs. If they're the 'CJPP' springs in the spring rate spreadsheet, they have a lot of drop (1.5"-1") and not much extra spring rate. You may be hitting the bump stops a lot.

I'd also be curious to know your actual alignment. You may want more camber than you have. More camber won't help your tire wear on a daily driver, but it can help the handling a small amount.

If your shocks are Konis (and valved like normal Konis) then you'd want them turned up pretty high for aggressive driving. Maybe not to max, but 75-90%. At speed and driving hard, that stiff feeling is the feeling of control. Yeah, if feels harsh at lower speeds over rough roads, but that's the best those shocks can do.

Tire pressures? Those tires have pretty soft sidewalls and might feel a bit mushy when driving hard at lower pressures.

My main advice would be to go ahead and run 4 or 10 autocross events. Ideally get an experienced muscle car driver to ride along with you and give you some thoughts.

 

[Grintch]

You have suspension parts from vender A, B, C, and D. It seems very unlikely they were designed to work with the other venders parts. Mixing and matching sometimes works, sometimes doesn't. In particular, I would try to avoid mixing springs, shocks, and roll bars that are not designed to work together.

If the car feels loose, step one would be to stiffen up the front anti-roll bar.

I had an early issue with my car where the alignment drifted off, because the mechanic didn't use the proper torque values (the beefy Mustang tends to require 2x the torque on suspension bits than say a Miata or GTI).

 

[SDAMike]

What feels wrong?

The only thing that sticks out is your springs. If they're the 'CJPP' springs in the spring rate spreadsheet, they have a lot of drop (1.5"-1") and not much extra spring rate. You may be hitting the bump stops a lot.

I'd also be curious to know your actual alignment. You may want more camber than you have. More camber won't help your tire wear on a daily driver, but it can help the handling a small amount.

If your shocks are Konis (and valved like normal Konis) then you'd want them turned up pretty high for aggressive driving. Maybe not to max, but 75-90%. At speed and driving hard, that stiff feeling is the feeling of control. Yeah, if feels harsh at lower speeds over rough roads, but that's the best those shocks can do.

Tire pressures? Those tires have pretty soft sidewalls and might feel a bit mushy when driving hard at lower pressures.

My main advice would be to go ahead and run 4 or 10 autocross events. Ideally get an experienced muscle car driver to ride along with you and give you some thoughts.

If I had to narrow it down to just 2 things that feel wrong, its that Im not sure what the ass of the car is going to do (initially and into a turn) and that when I hit bumps the front of the car feels like it shimmys and shakes.

Yes they are the CJPP springs. I cut the bump stops way down, but I can double check.

Funny you mentioned the tires, that was my first thought when they came in was uhoh those sidewalls are soft. I think I have them about 40-42 PSI, could I run more?

 

[SDAMike]

You have suspension parts from vender A, B, C, and D. It seems very unlikely they were designed to work with the other venders parts. Mixing and matching sometimes works, sometimes doesn't. In particular, I would try to avoid mixing springs, shocks, and roll bars that are not designed to work together.

If the car feels loose, step one would be to stiffen up the front anti-roll bar.

I had an early issue with my car where the alignment drifted off, because the mechanic didn't use the proper torque values (the beefy Mustang tends to require 2x the torque on suspension bits than say a Miata or GTI).

I hear ya on the parts, if I could do it over again I would do it different. All of it.

Thanks I'll definitely try the next setting on the front sway bar.

 

[Sham_POW]

If those springs have that much (1" to 1.5") of a drop, you're likely getting bumpsteer. That may be the source of the front-end shimmy. Steeda has a correction kit for it.

 

[Grintch]

Recheck the alignment too.

My issue resulted in the rear toe going well out of spec, resulting in the rear end having a bit of a mind of its own. Took two tries to fix, as both times the mechanic used his normal torque values without checking the proper spec for the Mustang (which was 2x because the Mustang uses bigger fasteners).

Easy example - wheel nut torque
Mustang 145 ft-lb (14mm stud)
WRX 70 ft-lb (12mm stud)

 

[NightmareMoon]

If I had to narrow it down to just 2 things that feel wrong, its that Im not sure what the ass of the car is going to do (initially and into a turn) and that when I hit bumps the front of the car feels like it shimmys and shakes.

Yes they are the CJPP springs. I cut the bump stops way down, but I can double check.

Funny you mentioned the tires, that was my first thought when they came in was uhoh those sidewalls are soft. I think I have them about 40-42 PSI, could I run more?

No, I'd back off and run softer. 40psi is VERY high. Most of these tires start to loose performance beyond like 37psi (HOT) IMHO,YMMV, etc etc. That explains some of the shaking. Stiffen shocks, soften tire pressure. Try like 34 or 35 cold pressures (tops) and for gods sake, keep them under 40psi. The tire starts to make contact only in the middle, running lower pressure should let you use more of the tire. It might feel worse based on initial feel, but it should grip better.

Autox practice will help you understand the car dynamics and it will get more predictable over time. Mustangs can be kind of weird. They're heavy and a bit soft compared to some other sports cars. Driving them well at the limit takes practice. Highly recommended. Check your ego at the door and commit to sucking for a while. People who think they are great drivers usually get a pretty hard slap in the face when they try autocross. Nobody is any good when they start.

Short cut bump stops and soft low springs I think you're going to get some awkwardness as you contact the bump stops.

If you don't have the steeda geometry correcting front control arms, I'd definitely look at those considering your 1.5" drop. (I'd just get the package deal with the bump steer). I'd really be interested to see how the car feel changes with those two parts.

If the rear of the car seems unpredictable, there are some parts (braces, and bearings to control dynamic toe and some of the control arm/subframe movement) which can make it a lot more predictable when you're breaking traction or spinning wheels/sliding under power.

 

[SDAMike]

Recheck the alignment too.

My issue resulted in the rear toe going well out of spec, resulting in the rear end having a bit of a mind of its own. Took two tries to fix, as both times the mechanic used his normal torque values without checking the proper spec for the Mustang (which was 2x because the Mustang uses bigger fasteners).

Easy example - wheel nut torque
Mustang 145 ft-lb (14mm stud)
WRX 70 ft-lb (12mm stud)

I wouldn't doubt alignment is off. I had a nightmare of a time even finding a shop to do it around here. I actually took it to this shop 4 times to get it where it is at and they kept on giving the car back where the steering wheel was cocked to the left even though it drove straight like it wasnt zeroed. Finally the last time after bitching the wheel was back to where it was. They showed me on the machine the specs and it was pretty close to the BMR specs but I cant recall what exactly they were.

Its kind of been a nightmare with this car in general so far.

 

[SDAMike]

No, I'd back off and run softer. 40psi is VERY high. Most of these tires start to loose performance beyond like 37psi (HOT) IMHO,YMMV, etc etc. That explains some of the shaking. Stiffen shocks, soften tire pressure. Try like 34 or 35 cold pressures (tops) and for gods sake, keep them under 40psi. The tire starts to make contact only in the middle, running lower pressure should let you use more of the tire. It might feel worse based on initial feel, but it should grip better.

Autox practice will help you understand the car dynamics and it will get more predictable over time. Mustangs can be kind of weird. They're heavy and a bit soft compared to some other sports cars. Driving them well at the limit takes practice. Highly recommended. Check your ego at the door and commit to sucking for a while. People who think they are great drivers usually get a pretty hard slap in the face when they try autocross. Nobody is any good when they start.

Short cut bump stops and soft low springs I think you're going to get some awkwardness as you contact the bump stops.

If you don't have the steeda geometry correcting front control arms, I'd definitely look at those considering your 1.5" drop. (I'd just get the package deal with the bump steer). I'd really be interested to see how the car feel changes with those two parts.

If the rear of the car seems unpredictable, there are some parts (braces, and bearings to control dynamic toe and some of the control arm/subframe movement) which can make it a lot more predictable when you're breaking traction or spinning wheels/sliding under power.

I bumped the tire pressure up because I was trying to get rid of the mushy wet noodle feeling in the rear, which it did seem to help. But sure I will try to drop the pressure and stiffen up the shocks more though.

I will be the first to admit I'm no expert here and probably am doing, and also bought, stupid shit.

I actually do have a steeda bumpsteer kit, I do most of all of my own work but I cant do that, so finding someone to install it correctly is another dilemma though.

Exactly which Steeda arms are those?

 

[shogun32]

so I turned the shocks up and that helped address that. But the ride quality def. took a hit.

can you provide actual settings instead of 'hand-waving'?

IMO poor choice of spring - too little rate, too much drop. Get some 250/900 or so rates.
keep the bars at full soft. Bars should be the very last thing to change out IMO.

 

[Norm Peterson]

Maybe worth noting: I have tried messing with the shock and strut valving a few times. Full soft rode really nice but once I put on the new larger wheels and tires, the ass end felt like a mushy wet noodle, so I turned the shocks up and that helped address that. But the ride quality def. took a hit.

Sounds like the problem actually began with wide tires on relatively narrow wheels. Wheels of minimum-recommended width for your tire size are going to give you softer cornering response and slightly to somewhat less steering precision. Cranking up the damping is at best a quick-and-dirty band-aid, but did you at least try a couple of smaller adjustments?

As mentioned, 40 psi is way too much, even if that was a hot pressure. Combined with too much rebound damping will make for a harsh ride over rough roads and expansion jointed concrete.

As for springs, something with more rate and less drop would have worked better. Those things matter more than whether or not they're part of somebody's suspension kit in a box.


Norm

 

[SDAMike]

can you provide actual settings instead of 'hand-waving'?

IMO poor choice of spring - too little rate, too much drop. Get some 250/900 or so rates.
keep the bars at full soft. Bars should be the very last thing to change out IMO.

Not sure what you mean by hand waving. My best guess is I am in the middle of the full range of adjustment of the shocks.

I know the springs weren't ideal either, but was factoring in looks too ( I know, another not a great move...I am full of them lol)

 

[SDAMike]

Sounds like the problem actually began with wide tires on relatively narrow wheels. Wheels of minimum-recommended width for your tire size are going to give you softer cornering response and slightly to somewhat less steering precision. Cranking up the damping is at best a quick-and-dirty band-aid, but did you at least try a couple of smaller adjustments?

As mentioned, 40 psi is way too much, even if that was a hot pressure. Combined with too much rebound damping will make for a harsh ride over rough roads and expansion jointed concrete.

As for springs, something with more rate and less drop would have worked better. Those things matter more than whether or not they're part of somebody's suspension kit in a box.


Norm

Yeah thats definitely when the mushy ass feeling started.

I started the shocks at full soft and went up about a 1/4 turn at a time until it felt better.

Im assuming going down tire size would help, but to what size, and if so what recommended brand?

 

[Labradog]

I like the Conti ECS. 275/40 or 265/40 will fit better on your 9.5" wheel for spirited driving. Other popular tires are Michelin's PS4S or the Firehawk Indy 500 as a more budget-friendly option

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