Vinnie Kung
July 7, 2014

While looking the part and having all the horsepower we need, Project BYOB is more like Project BLOB when it comes to attacking corners like anything more than a stocker. And if you've ever spent time wheel-to-wheel or just a day on an open track in a showroom-fresh GT, you know that the stock underpinnings are just barely adequate for a 412hp setup, let alone one with 567 horsepower at the wheels. With that, our project car is in dire need of a suspension suitable for the occasional track day, and the drive to and from a weekend of hooning.

There are several companies that offer great suspension kits for the S197 and all fundamentally do two things—crank up handling and improve appearances by lowering the car. Most will do the job, but will cross the line somewhere, be it performance, durability, or ride.

For this Stang, we stepped up to Kenny Brown's AGS 4.0 suspension. Instead of simply swapping in lowering springs and cranking up the shocks to full kill, a more thorough approach is used by Kenny Brown to address several key factors that will improve not only driver feel, but contact with the road during turn in, geometry change during suspension travel, and instant roll center.

Kenny Brown’s AGS 4.0 comes with Super Grip tubular lower front control arms, adjustable lower rear control arms, adjustable upper, and a roll center correction kit that upgrades the factory Panhard-bar setup. Part number KB-28690 lists for $2,516 and can be upgraded with the Eibach adjustable front stabilizer bar (PN EIB-35125-310, $289) and the full-on, no-holds-barred Eibach coilover kit with dampers (PN KB-Eibach-Level-1, $1,795). We decided that if we’re going to lie on our backs and do a suspension, we’re going to do it right with the best of everything out there! No games, son.

Together, this not only inspires confidence at the limit, but more importantly, provides a stable and predictable environment to get the most of what a live axle Mustang can provide. As Kenny Brown told us, "AGS 4.0 represents my fourth generation of AGS—Advanced Geometry Suspension systems. The key word is system, as the entire package is engineered to work together and articulate as a cohesive unit. I learned early in my career that the real speed is in the chassis and suspension."

He continues: "The Mustang has what is called a positive-roll front suspension, meaning the more the car rolls the more positive camber is gained in the outside wheel (opposite of what is needed). When a Mustang rolls too much, the front roll center (which is already very low) moves in the wrong direction, which is why stock Mustangs push like dump-trucks the harder you drive them.

"From racing and building Mustangs for the past 28 years, I know it takes a lot of spring in the front to make a Mustang turn on track. The springs support the platform, but it's the shocks that have to dampen the oscillation between the chassis and the unspring weight initiated by the road surface." Enter Eibach.

"The first product in this collaboration is the Kenny Brown/Eibach Street Sport Coilover Kit, with my spring rates and my shock valving to match. It comes with adjustable spring perches for adjusting ride height, and for the more advanced drivers, setting corner weights.

"You have the results in the BYOB Mustang—good, firm handling without a harsh ride. It has great performance handling with a sporty ride, and is fully track capable, where most Sport spring packages really are not."

With Kenny Brown's blessing bestowed upon BYOB, we decided to tackle the AGS 4.0 installation ourselves in our home shop, which in truth is very average. No lift, no special tools, just a good set of handtools and a creeper. For the heck of it, we also used a fresh pair of Mechanix gloves, since we plan to have dinner with the wife this weekend and we want to keep bleeding and scarring to a minimum.

While the coil spring and damper combos by Eibach are a straight- forward in-and-out swap, the hard parts such as Kenny Brown's rear Panhard-bar kit and front tubular K-member and control arm setup require slightly more specialized tools. So, let's start spinning wrenches, shall we?

The Backside of the Story

Starting with the rear, we removed the factory Panhard bar and lateral brace above it to make way for the new parts. Kenny Brown lowers the car's roll center by dropping the attachment point of the Panhard bar a good 3 inches. To do this, a new relocation bracket needs to be installed, and this requires some drilling. The end result is that the car no longer feels like it's toppling over when taking long sweeping turns. As we like to call it, "the leaning tower of Mustang" will be no more.

To accompany the new hard parts, we installed Kenny Brown's U-link rear upper control arm, which is fully adjustable for length and replaces the squishy factory piece, frame mount and all. The lower rear control arms are also adjustable for length. When combined with the new axle mounting brackets (designed to reduce dive under braking and move the lift center rearward under acceleration), the car will not feel perpetually torqued over when accelerating as that 8.8 claws for traction and directional control at the same time. If you've been pounding on Mustangs as long as we have, you know what we mean.

Moving To The Front

To improve the handling of any Mustang, you need to address the front half more aggressively than the rear. This is why Kenny Brown goes all-out and swaps out the entire front suspension system, control arms, struts and all (and optionally, even the K-member.)

Now, we know what you're probably thinking. That tubular K-member is designed to take weight off the front end, and that is true. But what Kenny Brown does is pure magic.

With the stock geometry gone, Kenny went to town, relocating the two pivot points for the lower control arms, which is the key to improved handling at the limit. He adds significant caster without strut plates, improves TOOT (toeout on turns), which helps camber gain as the steering angle increases, and all the while, increases wheelbase for a better ride.

Altogether, it plants the front tires proportional to steering angle, reduces nose dive, and provides incredible feedback through the steering wheel so you know where you stand in relation to that contact patch. Rounding things out in front are the Eibach coilovers, tuned specifically to Kenny Brown specifications, and an Eibach antiroll bar, which is adjustable. The rear sway bar remains for balance, as the goal is to control that wild-and-wooly live axle.

Taking our Harbor Freight 20- percent-discount coupon (which we ripped out of our magazine—how ironic), we bought one of its engine support tools, so you can do like we did and drop the whole K-member without needing an engine hoist (which, incidentally, was on sale that week.) With the stock crossmember, control arms, and other items out of the way, we simply slipped the new Kenny Brown tubular crossmember into place, used most of the factory hardware, and cranked everything down.

Check out the captions and sidebars for the details as we get dirty again, all for the sake of speed.

01. A complete chassis-stiffening kit also comes with the AGS 4.0 suspension and welds into place. Essentially, this kit stiffens the outer floorpan’s flange, where it meets the lower rocker panel and ties it to the factory subframes to spread load out between the front and rear of the car evenly.

02. The front K-memberr that Kenny Brown offers is an engineering masterpiece. Fabricated from square steel tube, this robust piece not only sheds a bunch of weight (factory is 79.7 pounds, KB is only 37.1), but it also improves suspension geometry by modifying the mounting points of the front lower control arms for increased “anti-dive.” The best part, it’s fully compatible with the electric power steering in our ’11 GT. It’s part number KB-49710 and lists for $769.

03. The first thing we did was swap out the rear lower control arms and install the lower control arm relocation brackets onto the rear axle housing. The Kenny Brown arms are adjustable and reduce 2.2 pounds off for each arm in partially unsprung weight. We set them up to be the same as stock length for now, and can tune things later.

04. The upper control arm is where a lot of the magic happens in an S-197 Mustang. Aside from being the sole pivot point for anything above the centerline of the 8.8, it also has to transfer a bunch of forward motion to the ground. To allow suspension tuners the ability to dial in their combination for varying street or track conditions, the tubular piece by Kenny Brown has a single-adjustable joint at the forward end of the control arm. As a baseline, we started off with factory length.

05. Next up, we removed the factory rear shocks from inside the trunk area. With the rug pulled back, a cordless impact driver removed the upper nut with a 15mm-deep socket. The suspension can now be lowered and the factory springs taken out.

06. The stock springs are slightly progressive in rate, based on the varying coil diameter, but same wire size. In its place, Kenny Brown uses Eibach coils with billet aluminum adjusters that are seated on the rear axle’s perches. As a baseline, we threaded the collars about halfway, but learned later on that they had to be pretty much bottomed out for desired ride height.

07. With the new springs in place, we then installed the Eibach Pro Street S shock absorbers into the factory locations and re-used the factory hardware on the lower end.

08. We then installed the new Panhard-bar relocation bracket onto the left of the rear axle and with the one hole drilled, used the supplied hardware to attach it. On the passenger side, we replace the frame-mounted Panhard-bar bracket as well, effectively lowering the pickup points by nearly three inches to correct the roll center of the car, which makes a great difference when making transitional turns.

09. The adjustable Panhard bar is key because when you change ride height in any S-197 Mustang, there is a risk that the 8.8 is not centered within the car. We started by going with the stock length, but later saw that we actually had to run it shorter so that the rear axle was correctly centered.

10. The bump stops then need to be swapped out. Held in place with a small bracket on each side of the rear axle, they and prevent the car from bottoming out prematurely.

11. To tackle the front end, we decided to simply drop everything out from underneath, meaning that the K-member and lower control arms would be lowered out as an assembly. To do this, we went with a Harbor Freight engine support bar that holds the engine up with chains and sits on top of the strut towers and started unbolting everything from underneath. It’s a pretty sweet tool for only $100.

12. The factory K-member is not a terrible piece, but when we can save weight and get better suspension geometry, you bet the stock piece is bound for the dumpster. Waiting for my metal guy to come by this week. He’s going to love this one!

13. With the engine supported above, thanks for Harbor Freight and their magazines of coupons, we can raise the Kenny Brown crossmember into place. This requires some patience as we line up the steering rack and the bolts in the front framerails. Note that on the passenger side of the steering rack, we used a tie-down strap to hold it in place to prevent unnecessary strain on the wiring.

14. As the new crossmember is fastened to the framerails, we then used the supplied hardware to bolt the rack into place.

15. The engine mounts provided offer you the choice of polyurethane or rubber for isolation and use a through-bolt design for optimum strength.

16. Next up, we bolted the rear of the lower control arms into position, re-using the factory hardware.

17. The front bushings of the lower control arms are offset, if you notice, to help bring the control arm slightly forward for increased caster at the wheel, creating a longer effective wheelbase.

18. The Eibach coilovers can use the factory upper strut mounts and go right into the strut towers with no special mods.

19. The lower strut mounting flange has an oval opening for the upper bolts that allow you to adjust static camber at the wheel with the factory bolts. We centered everything for now and dialed in 1.5 degrees of negative camber once we got onto a wheel alignment machine.

20. With the struts bolted in place, we then used the coil ride height adjusting tools provided by Kenny Brown to lower the springs about a third up from the bottom of the adjustment range. Use the tool on the left to hold the lower ring while you use the tool on the upper ring to actually tighten things. No reason to get over-zealous with excessive torque as these will hold adjustment with a moderate pull.

21. With the Eibach front sway bar in place, we chose to use the center hole and tightened the end link down. As we get onto a track, we will play with this setting to see how this adjustment affects handling.

22. We thoroughly greased the anti-sway bar bushings and tightened everything down to the radiator support, which we previously replaced with a lightweight Steeda piece a few months back.

23. With everything completed underneath, it was time to gaze upon our hard work. With the factory splash pans bolted back into place, we were ready to tackle our local canyon road in SoCal.

Heritage of Kenny Brown Advance Geometry Mustang Suspension Systems
1987-1992 AGS Gen-I (Saleen-R & Fox Mustang)
Revised Front K-Member Geometry
1993-2000 AGS 2.0 Gen-II (Fox Mustang, SN-95 Mustang)
AGS Fixed-Strut Front Geometry
AGS TracKit Plus Rear Geometry
2001-2004 AGS 3.0 Gen-III (SN-95 Mustang)
AGS Tubular K-Member and Control Arms
AGS Rear IRS Module
2005-2013 AGS 4.0 Gen-IV (S-197 Mustang)
AGS Tubular K-Member and Control Arms
AGS Three-Link Live Axle Rear Geometry

Five Minutes with Kenny Brown

Kenny Brown has been in the game for decades. Aside from being an accomplished driver, his technical ability continues to propel him to the forefront of Mustang suspension technology. Looking back, it is amazing how much has happened in his 40-plus years as a racer and engineer. We had the opportunity to ask him a few questions, so let's see what the man has to say.

MM&FF: What's your take on spring rates?

KB: Springs are one of my favorite subjects. Springs are a topic all their own in my new Speed Secrets newsletter and blog series, where I give tips, tricks, and secrets about how to add speed to your Mustang along with Mustang-specific driving tips and set-up guidance.

A little background: Back in the '70s and '80s, when I was racing SCCA Formula Fords, Super Vees, Formula Atlantic, and S-2000s, we always had a selection of springs in the trailer. The reason being different tracks took different spring rates to be fast. Most companies and customers in the aftermarket just buy sport springs from a manufacturer and install them without knowing why or the spring rate as long as it says sport on it.

To put my spring philosophy into perspective, most front sport springs for S-197 Mustangs are in the 275- lb/in range. My Street/Sport package is in the 400-lb/in range. To put that in perspective, my Club Sport packages are in the 550- to 650-lb/in range, Track Sport is in the 600- to 750-lb/in range, and Race is in the 750- to 950-lb/in range.

A lot of people will buy a set of sport springs and put them on stock shocks. The shocks were tuned or valved for the stock springs, so going up on spring rate over what the shocks were designed for will ultimately produce poor ride quality, and the shocks will wear out much faster. This is why I have always recommended adding sport springs and sport shocks to go with them.

Over the years, I have amassed a pretty thick notebook on shock dyno data (which graph the valving as a function of force and velocity) of everything from street to sport to race shocks. I have been doing this so long I know what I want in valving to balance ride, handling, and performance with specific spring rates for each specific application.

MM&FF: Did you find the factory K-member lacking?

KB: I don't think of it as lacking, but definitely needing some weight reduction. Instead of designing all my geometry changes in the K-member as I have in the past, I engineered most of the changes in my Kenny Brown front control arm module. This gives the end user the ability to purchase the control arm module first without having to purchase the K-member, and in doing so, get the benefit of most of the geometry changes in one product instead of two. We had a lot of experience with the SN-95 K-member and control arm module that we introduced at the 2001 SEMA show, we just carried the concept forward to S-197. Again, it's an evolution of my AGS suspension systems.

MM&FF: What separates Kenny Brown Suspension systems from other manufacturers?

KB: I think first and foremost, experience, experience, experience. I have been doing this for a long time. What separates me from most, for the first half of my career I made my living out of my toolbox, working on sports cars and road racing. I am also a driver and have logged tens of thousands of miles racing, testing, driving, and developing suspensions, fully prepared race cars, and performance track and street car packages. I pretty much know every nut and bolt, where it goes, and what it does.

Plus I am a student of how suspensions work. I study a group of parameters I developed to monitor the suspension during driving and cornering events. I look at six to eight points through a corner, and study what the suspension/tire contact patch is doing at each, and what changes will improve the contact patch during each. Grip is all about how much tire you can put on the road.

I also try to keep it as simple as possible for our customers. We like to say I do all the engineering, testing, and developing for our customers—all they have to do is bolt it all on and go.

MM&FF: Has work begun on the 2015 Mustang?

KB: I am really excited about the 2015 Mustang. As you may recall, I know IRS cars from my early racing days, and Kenny Brown was one of the only companies that had a full suspension line for the SN-95 IRS Cobras. As of this writing, we are through the planning stages and starting the development phase for the 2015 Mustang.