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!