Making a non-PP GT handle like a GT350

[Zissou]

After driving a GT350 (non magnetic ride) I've determined that's my target for the blend of handling / comfort for my DD S550. The hunt is on to transform my non-PP GT (Cali Special) into this. The other benchmark is an e92 M3 for that blend of comfort and handling. Going for "stance" is not what this is about, but a 1" drop or so would look nice. Looking to the experts here for advice.

About my driving: This is for street (aggressive street). I might try to get on the track (maybe VIR or autocross), but it hasn't happened with my other cars so who knows. This is also going to be my daily driver as soon as I sell my Fiesta. I live in an area with smooth, mountain roads.

So the obvious and probably biggest piece are the tires. The plan is to do 19x10 with 275 or 285 summers in a square set up, or possibly those up front with a 19x11 in the rear, but that doesn't seem necessary given my essentially stock levels of power. This part seems to be the most straight forward.

The more complex piece are suspension bits. There's a few routes I've envisioned.

Route 1: Package (progressive springs)
First thought was the FRPP Track Handling Package (link for reference) https://performanceparts.ford.com/part/M-FR3A-M8
But then I got to thinking, is that going to be too rough of a ride? Is it going to be overkill? To that end, there's also the FRPP Street Handling Package https://performanceparts.ford.com/part/M-FR3A-MA
So first off - which is closer to what the GT350 comes with? Either?

Similarly there's the Steeda option, though I haven't read much about it. https://www.steeda.com/steeda-s550-mustang-gt-non-performance-pack-handling-kit-15-16-gt-555-2354.html

After reading the incredible and extensive "My Complete Suspension" by [MENTION=10530]MustangCollector[/MENTION]
I've come to wonder if the progressive springs in those two packages would not be better suited with linear springs (link to that thread) https://www.mustang6g.com/forums/showthread.php?t=22036
Since I don't want to buy things twice I'm wondering if I should look elsewhere.

A package makes things simple and I like knowing things will play well together. The last thing I want is to start a thread asking why is my mustang trying to kill me, or why does it drive like a box of rocks.

Route 2: Linear springs + ??
I recently drove a PP mustang that had the springs swapped out for Vogtland (not sure if linear or progressive) and it was wonderful. Comfortable, but no nose drive.

If we're doing linear springs to get where I want to be then the top options seem to be BMR, Steeda Ultralight, and Eibach Pro.

If that's the route then which shocks / struts are best matched to them?

Route 3: Coilovers
From what I've researched the KW v1 or ST coilovers seem to be most what I'm looking for. But I'm wondering if that's overkill for my purposes. I also don't want to just blow money if it's not needed.

Additionally I'm assuming sway bars will need to be added for routes 2 and 3, and toe links and maybe some other parts. I've heard of the free sway bar mod, but I'm not above just buying one since it would be harder to mess things up that way.

Anyways, looking for advice here to get to my goals.

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[BmacIL]

Route 2: BMR SP083 handling springs + FRPP track handling dampers. The dampers are GT350 monotubes with blue paint. The SP083 springs are very nearly GT350R rates (a little stiffer out back) and handle incredibly well. This combination rides and handles like a sports car. I did a trip to Austin and back with one of my best friends in his track pack GT350 and I was happy to feel how similar his and my car felt overall. The magneride was obviously a little better riding in some situations but really not that much.

Feel free to pm me for any questions. I daily drive mine.

 

[BlownGP]

Route 2: BMR SP083 handling springs + FRPP track handling dampers. The dampers are GT350 monotubes with blue paint. The SP083 springs are very nearly GT350R rates (a little stiffer out back) and handle incredibly well. This combination rides and handles like a sports car. I did a trip to Austin and back with one of my best friends in his track pack GT350 and I was happy to feel how similar his and my car felt overall. The magneride was obviously a little better riding in some situations but really not that much.

Feel free to pm me for any questions. I daily drive mine.

Very good info.
Thanks

 

[Zissou]

Route 2: BMR SP083 handling springs + FRPP track handling dampers. The dampers are GT350 monotubes with blue paint. The SP083 springs are very nearly GT350R rates (a little stiffer out back) and handle incredibly well. This combination rides and handles like a sports car. I did a trip to Austin and back with one of my best friends in his track pack GT350 and I was happy to feel how similar his and my car felt overall. The magneride was obviously a little better riding in some situations but really not that much.

Feel free to pm me for any questions. I daily drive mine.

This was 100% the insights I was looking for - thanks!

How about some of the other suspension components. I see from your signature you have BMR Cradle Lockout, BMR Vertical Links, PP Chassis Bracing, PP Rear Sway Bar. Would you recommend any/some/all/none of those for what I'm looking to accomplish?

 

[BmacIL]

This was 100% the insights I was looking for - thanks!

How about some of the other suspension components. I see from your signature you have BMR Cradle Lockout, BMR Vertical Links, PP Chassis Bracing, PP Rear Sway Bar. Would you recommend any/some/all/none of those for what I'm looking to accomplish?

Yes I most definitely would. The cradle lockout and all the PP chassis bracing makes a big difference. I have done all of these individually so I can tell you the effects of each.

 

[Andrewg]

Lethalperformance are offering a decent BMR package at the moment for a good price. https://www.lethalperformance.com/bmr-suspension-2015-mustang-bread-and-butter-package.html

I've got most of the components in the package with the exception of the toe rods on stock springs and shocks and just those parts made a huge difference to the overall feel of the car. Firmer and more confidence inspiring.

 

[EFI]

The dampers are GT350 monotubes with blue paint.

Are the rear shocks also from the GT350? Because aren't those not compatible with the GT control arm?

And why not the GT350 springs to round out the package? Since the BMRs are similar in rates, are those any better?

 

[Roadway 5.0]

So much pushing for monotubes and intense spring rates...I understand this is what is found on the GT350 (non-MR) but they are not my recommendation for a street car.

I too daily drive my car, hunt mountain roads, and will likely never see a track. I also sought a ride/steering response similar to an E92 M3 (I came from the BMW world and even reupholstered my steering wheel to these specs) but wanted a touch stiffer.

My conclusion is in the video I made below. I’d argue that this setup, along with PP bracing and brakes, is a close-enough solution to the GT350 (non MR/-R) suspension in performance but will give you a slightly more tame ride (a bit less rear rate; twin-tube dampers).

Roadway 5.0’s S550 Mustang

Many strong opinions are present on this topic...choose wisely and good luck!! :cheers:

 

[BmacIL]

Are the rear shocks also from the GT350? Because aren't those not compatible with the GT control arm?

And why not the GT350 springs to round out the package? Since the BMRs are similar in rates, are those any better?

They're the same internals but the GT mounting. You could definitely do GT350 springs. There are tangible gains to some lowering, though. IMO the BMR wheel rates are better for this car just slightly.

 

[BmacIL]

FYI, ~230 lb/in wheel rates are not intense, nor are monotubes inherently punishing as some would have people believe. The valving is key. Twin tube and monotube can both be tuned to handle and ride well. Monotubes, via their design, are going to be more consistent and have less hysteresis. You won't find anything else on high end coilovers (>$2500), though often with remote reservoirs to get more travel.

 

[qtrracer]

One of the reasons the GT350 handles so well is because of its monster wheels/tires. Take those off and put non-pp wheels/tires on and you'd be surprised at the handling degradation.

You have to understand that the dampers control how fast the springs react to driver inputs and the road surface. So in dive while turning, you want the front outside spring to travel (compress) enough to load the outside front tire while keeping the inside front with as much tread on the ground as possible. This is both a damper and spring choice issue but the damper controls have fast this occurs. Non-adjustable dampers assume a comfortable ride, even "sport" dampers. It's easy to over spring these choices.

At the same time, the rears must also react generally throwing weight forward onto the front tires for increased front grip. But we need to balance this so the transfer is controlled and does not overpower the outside front tire (which is doing most of the cornering work). While this is occurring, the inside rear is unloading just enough to allow the car to rotate, while the outside rear is going into compression and putting weight into that tire. I know you've seen cars lift the inside rear. If that tire is off the ground, it is not adding anything to grip and likely the other outside tires are overloaded.

The key to all of this is make certain the dampers can control the springs so the springs don't overpower the dampers, or the damper valving overpower the springs.

If you want to the car to handle better, put more rubber on the car, and buy some double adjustable dampers. The bars and springs and lockouts and all that stuff are not needed as much as the tires, wheels and dampers.

 

[wildcatgoal]

As of 2-hours ago, I've installed the following combo three times with rave reviews:

- Swift Spec R springs
- Steeda Fixed (or Adjustable) dampers
- Steeda rear shock mounts

I've run the Swift springs and adjustable Steeda dampers myself when I daily drove my car. I have not been in/driven a car with a better all-around feel (to my taste).

Been in a few cars now with the Ford Track dampers and varying springs -- all of them weren't as compliant as my car with Steeda dampers and Swift springs.

Monotubes have advantages for sure, but the capabilities of today's twin-tube designs disprove a lot of the rumors and misinformation being injected lately.

Steeda tests its shocks and springs (and other parts) on track and has proven their performance improvements on and off track. Their EB car outpaces GTs (and in a few cases, GT350s) on track.

 

[NightmareMoon]

If by handling, you mean raw grip, thats nearly all just tires. They're the only thing in contact with the ground. Choose the stickiest, widest summer tire you can find and you'll have a car which can out corner almost anything shy of a Porsche GT3 or well set up S2000.

If you want faster transitions from left/right or faster weight transfer into and out of corners, then upgraded shocks and stiffer sways can do that. Swaybars (and springs) can reduce some body roll and increase transition (reaction) speed from left to right, but they wont generally increase grip. Neither will shocks, but they can control how that grip comes and goes with respect to the driver's inputs.

If you also want to kill some nose dive or lift then look at stiffer spring rates, but be wary of lowering sprigs that aren't much stiffer than stock (or else you'll be on the bumpstops. I dont personally think that should be a major goal. The slower softer weight transfer from softer springs helps grip when braking or digging off the line. A lower car can get a little extra raw grip just from the lower center of gravity, but the more you lower the more you're going to need heavier springs and stiffer shocks to control them and keep you off the bumpstops (which should be trimmed a bit shorter BTW in a lowered car). Stiffer isnt good for grip, unless that stiffness is keeping you from hitting the limits of your suspension travel. Sooo its not so simple. A lot of choosing spring rates depends on the roads in your area, and how hard you are driving (see tires).

If you do go with stiffer springs, then upgrading the shocks too is basically mandatory or the ride will get bouncy and the car may generally behave badly.

Adjustable swaybars and adjustable shocks can be used to fine tune how the car behaves at the limits of grip. If you'd just prefer to not reach those limits in the first place, then we're back to tires.

If you can, you'll want the widest wheel you can find and fit under the fenders that still allows you to run your chosen tire. For most mortals, a 285 tire on a 10" wheel is pretty good, as 11" wheels are hard to fit in the front. Going with wider wheels and tires in the rear than the front will generally cause the car to understeer more and oversteer less frequently at the limit, but there are many other factors, such as shock and swaybar settings.

 

[wildcatgoal]

^ Correct-a-mundo!

 

[scherisho]

My humble opinion....
I recently added some goodies to my car. 2015 GT. My car came with 20 inch wheels and I have all of the performance pack bracing expect for the the strut brace. I added the strut brace, BMR minimum drop springs SP763??, steeda rear shock mount, ford racing track strut and shocks package M1800??, and the CB005 cradle lockout. The ride is firmer and not harsh. I’ve actually already have become used to the ride and the roads around here are ok and not the best. Stance is perfect and handling is great. I have new rims and tires coming this week and the tires will be about a half inch bigger in diameter than the stock 20 tires. The little extra sidewall will probably smooth the ride just a bit more. Regardless I’m very happy with the setup I installed.

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