Evan J. Smith
November 8, 2013
Photos By: Robert McGaffin

Passion, performance, and persistence are merely a few words to describe Kenny Brown, the man behind the performance suspension company that bears his name.

Kenny, who has a long history in racing and building Mustang suspensions, race cars, and street-performance vehicles, has truly utilized his skills to develop Mustangs and the parts that greatly enhance on-track performance.

His latest lineup of Mustangs and components exemplifies a life-long engagement with enhanced braking, cornering adhesion, and the accompanying acceleration to rocket you off a corner. We've tested virtually every car he's developed, and now Kenny Brown Performance is back with the AGS (advanced geometry suspension) 4.0 and his 475hp 2011 GT track star he calls Ruby. Brown names all his Mustangs, he says it gives them character.

"The evolution of our AGS is really pretty basic," said Brown. "Every one of our past cars has been a progression that has let us learn what Mustangs want. First, you have to understand what the Mustang is, and how it works," he exclaimed. "It's a pony car with a heavy engine up front and a stick axle. The strength is the power and acceleration," he added.

As has been the case for nearly two decades, Brown invited us to put hard laps on his press car, the GT4-RS Autobahn Edition, at, of all places, Autobahn Country Club in Joliet, Illinois. It's a menacing beast, aggressive in its stance, and with proudly positioned components to take it far beyond stock.

The track, Autobahn Country Club, located about 45 minutes south of Chicago, is a private hot spot for driving and racing enthusiasts (read: members) who can access the track(s) daily. It can be arranged in three layouts, a North and South course, and/or a full track that links the two. Members enjoy a smartly appointed club house and a host of amenities. There are impressive Garage Mahal facilities, some owned by famous racers; a driving school; and a race team or two housed inside the gate. One member even arrived by helicopter during our visit.

Brown's systematic approach allows you to spec any '11-present Mustang with a multitude of options. His ultimate, the GT4-RS, offers race-car-like capabilities for terrorizing high-end sports cars. It's a track-ready street Mustang that's enhanced from every angle.

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"Improving performance boils down to understanding the car and the geometry to get what you want," says Brown. "The cool thing about the AGS 4.0 (a package including chassis support, relocated suspension links, bushings, and Boss-S EPAS and ABS) is the core. It corrects the geometry.

"The difference between a street, track, and a race car is just about spring and shock rates. I use a higher spring rate than most people, and I maintain ride quality with shock valving. Good shocks and good valving equals a good ride," he adds.

"Springs and shock need to be changed together. I make [the Mustang] easy to drive and that takes all the drama out. You can change the shocks and springs, and that's nice, but you're not really fixing anything. At the end of the day, it's about putting the biggest contact patch on the ground. It's not about the parts—it's about what the parts do!"

Trackin' Out

We met with Brown and his team on a crisp April morning and strapped into the red rocket to take on the technical 2.1-mile, 15-turn South Course. (We'd also drive the 1.46-mile, nine-turn North Course.) Ruby has all the makings of a track star, including fixed-back OMP seats and harness setup, a tightly arranged rollbar with unique swing-out side bars, and a functional aero package with a front splitter and tall rear wing that creates extra grip. It's also fashioned with custom air dams, a PBR heat-extractor hood, and cooling ducts for the brakes.

If there was anything missing, it was a nicer, more racy steering wheel. The base GT wheel is just plain boring, and as the centerpiece of the front office, I'd like to see that upgraded to the Boss wheel or something equally as nice.

Autobahn's North Course is great fun and smooth—precise driving is rewarded with quick laps. Overcooking corners will cost you as the track has a rhythm or flow that requires you to stay on line. Brown was adamant about me easing up to speed on the cold tires (and cold track), so I warmed up my brain as well as the Pirelli PZero Corsa tires wrapped on those spiffy KB/Forgeline Monoblock wheels as I familiarized myself with the new surroundings.

With the Mustang up to temp, I exercised the power, brakes, and handling. And with that came a big grin inside my helmet! The Ford Racing Boss-inspired 302 powerplant sounded glorious as it's spent gasses poured from the Bassani 3-inch exhaust. It revved effortlessly to redline and the grip was amazing. As I gained confidence, I moved my braking zones deeper, deeper, and deeper. Hitting the pedal on the Baer brakes was like dropping anchor—I slowed in control for each turn, feeling most of the time like I left room on the table. The system is comprised of its KB-spec'd Extreme 6-piston calipers (front and rear), 14-inch rotors at each corner, and cooling ducts to control temp.

"I like big brakes," Brown said proudly. "You need big brakes on a track car. The Bear Extreme Plus R setup is spec'd for us. The calipers are lighter, and you don't have to take them off to change pads, which is nice. We use really thick Hawk pads, which last longer and give more control over heat. When you're on track, you need pads that match the heat range. We see between 1,000 to 1,200 degrees at Autobahn, and 1,400 degrees at Road America."

He added, "The very best opportunity to pass in racing is under braking, so I look at how I can put the highest contact patch on the track at all times for maximum grip in cornering and braking, too. You can brake really late and the car comes down flat and controlled. It gives you the opportunity to close on someone and intimidate them."

While I didn't do much intimidating on this day, I did push the Mustang quite hard, and felt just what Brown stated. I was able to go deep in the corners, and also get back to the gas quick. And that allowed me to utilize the horsepower and make each straightaway a bit longer.

"But the next problem is getting around a corner," says Brown. "I try to build most of the camber gain in the turn, not in jounce. In the old days you had to run so much camber, the contact patch goes down to nothing. Stock, a Mustang wants to plow the nose and jack up in the back in a corner, so bringing the front roll center up and the rear down, prevents the body from rolling as much. In a corner, you're always waiting for the real axle to settle, by flattening out the roll centers the rear remains settled and you can get to the gas sooner," he added.

One of Brown's many goals is to make the Mustang balanced and easy to drive. Mission accomplished. His suspension setup keeps the car flat in the corners and limits dive under braking. "I've got JRZ single-adjustable coilovers and they help with balance. What I try to create is a balanced car with slight understeer. If you give [customers] too many things to adjust, they will not focus on driving. I ask, how can we give the customer the best possible experience? If it is easy to drive, it's generally easy to drive fast."

During my test, I concentrated on using smooth, aggressive inputs and the Mustang was sucked down into the track. It responded nicely under braking, as well as to turn-in, and handled trail braking nicely as well.

"We have people starting with the basics. So I always recommend enhancing chassis, suspension, brakes, and safety gear. Always start with the brakes. Then chassis, wheels, and tires. I work with the individual customer to design the best package for their budget, and we also offer special pricing through Victor Ford in Wauconda, Illinois.

Kenny Brown Performance has once again delivered not only a track-worthy Mustang, but a package that is sure to lead the pack, whether it's on the street, or at a track day lapping with Porsches, Bimmers, and Vettes. The KB Autobahn Edition Mustang appeals to our senses, from it's racy stance, to the performance, to the sound of the hopped-up Coyote. This pony is 100-percent legit.

Kenny Brown GT4-RS Autobahn Edition Mustang

• Ford Racing Boss 302 475hp crate engine
• JLT cold-air kit, SCT custom 92-octane calibration, JLT oil separators, Canton road-race oil pan
• Bassani headers with X-style mid-pipe
• 3-inch exhaust
• Bassani high-flow race mufflers
• Tremec Magnum XL direct-shift six-speed
• KB Track Sport carbon billet cutch
• KB Track Sport aluminum flywheel
• Quarter-Master aluminum driveshaft
• KB-spec torque-sensing differential
• Boss aluminum differential cover
• HD aluminum radiator
• Positive-flow radiator ducting
• KB HP engine oil cooler
Chassis Support
• KB jacking rails
• Heavy-duty strut-tower brace
• KB Matrix chassis support system
• KB Super Club cage w/swing-out door bars
• Kenny Brown GT-4 (AGS 4.0) Advanced Geometry Suspension system
• KB AGS 4.0 tubular K-member w/front lower control-arm module
• KB adjustable front sway bar
• KB bumpsteer and tie-rod ends
• KB AGS adjustable rear lower control arms w/double rod ends
• KB rear K-link upper control-arm module
• KB rear traction anti-squat geometry brackets and roll-center bracket kit
• Boss-S EPS track-tuned steering rack
Track/Sport Springs and Shocks
• KB-spec JRZ single-adjustable coilover shocks
• KB-selected Eibach springs for specific driver style
• Adjustable ride height
High Performance Brakes
• Baer Extreme-plus six-piston R calipers (front and rear)
• Stainless steel brake lines
• 14-inch ventilated rotors (front and rear)
• High-temperature brake fluid
• KB front brake cooling ducts (fascia to spindle)
• Boss-S track-tuned ABS module
Wheels & Tires
• KB/Forgeline Monoblock racing wheels 19x10-inch front; 19x11-inch rear
• Pirelli PZero Corsa Extreme Performance tires 295/30/R19 front; 305/30/R19 rear
• Side skirt splitters
• PBR heat-extracting carbon hood
• PBR Club Sport rear wing
• Front splitter w/custom fender air dams
• Custom graphics
• Driver left-foot dead pedal
• OMP Club Sport Racing seats
• Schroth Competition (HANS) harness belts
• Battery relocation to trunk
• Rear-seat delete
Serialization & Graphics
• Dash plaque and underhood production plaque
• Special exterior GT-4 graphics package
• Log book, setup, history, and maintenance info
• Setup class for your crew on your car
• Test day help to set up your car
• Driver coaching
KB GT4 Series Pricing (car not included)
GT4, Street/Sport Package $12,000
GT4-CS, Club/Sport Package $23,500
GT4-RS, Track/Sport Package $56,500
Ruby GT4-RS, Track Package $72,800