2011 Ford Shelby GT500: Suspension Walkaround
Yeah, I know. The word "Mustang" is missing in the above title. It's kind of silly because, after all, we can all see with our own eyes that the Ford Shelby GT500 is a Mustang. But Ford chose to leave "Mustang" out of the official model name of this car. My hands are tied.
But my floor jack and lug wrench are fully unbound. Let's get in there and see if we can see what it takes to turn a Mustang into a Shelby -- apart from stripes, badges and Cobra medallions, that is.
Like all late-model Mustangs, the front end of the GT500 is suspended by coil-over struts. Our GT500 has the optional SVT performance package, with includes, among other things, stiffer springs (20.5% up) that produce a lower ride height (11mm down) and "upgraded" front struts and rear shocks. "Upgraded" doesn't merely refer to red paint -- the valving within has been re-tuned to produce more damping force.
Like most front-engine rear-drive (FR) cars, the Mustang family uses the preferred "front-steer" arrangement, wherein the steering rack sits ahead of the front axle centerline. The 15.7:1 steering ratio used in the GT500 is the same found in all other 2011 Mustangs.
The GT500's L-shaped lower control arm (yellow) is made from welded steel and carries a single lower ball joint.
Here's another seemingly shared part: the front knuckle (yellow) is appears to be made of the same ferrous material found on other Mustangs, and the Brembo brake calipers mount to the same "ears" on the part. That makes sense because a Brembo brake upgrade is offered on the Mustang GT option sheet.
All Mustangs use lightweight tubular front stabilizer bars (yellow). According to Ford press materials, the Mustang V6 uses a front bar that's 34mm in diameter and the GT uses one that measures 34.6mm. It's hard to tell how significant this difference is because the wall thickness of a hollow bar is needed to quantify its actual torsional stiffness, but Ford doesn't provide that tidbit on the spec sheet.
The GT500 is listed as having the smaller of the two choices, the hollow 34mm bar. With the firmer springs and dampers that go along with it, this probably doesn't increase body roll so much as it reduces understeer. Bigger isn't always better.
On the other hand, it could be a typo on the spec sheet.
Meanwhile, the direct-acting stab link (white) is something you'll see on all Mustangs.
These four-piston Brembo brake calipers are standard on the GT500, and they squeeze one-piece 14-inch ventilated cast-iron rotors. As mentioned earlier, they're available as an option on the Mustang GT.
It would have been nice to have little scrapers like this (yellow) on the brake pads of our Ford Flex long-term car so we could have easily heard when the brake pads were getting too thin before it was too late for the rotors.
And speaking of rotors, this one is not held in place by a Torx-head or Phillips-head screw, it's held in place by a couple of push-on, screw-off washers (black). They go on sort of easy, but they're a royal pain to remove.
Moving to the rear, this profile view doesn't quite show us what's going on. We can see a spring, a shock, a stabilizer bar (black) and an aluminum-looking trailing arm (green), but we need to see more to figure out how the wheels are being held in position.
What at first looked like a silver trailing arm (yellow) is actually a trailing link. It has single-point mountings on either end, so we still can't see how the rear axle resists the torque reaction and stays in the correct orientation. Further up, we can see how the rear spring (green) simply perches atop the solid rear axle and nests in a cavity in the unibody. Meanwhile, that rear stabilizer bar mounting is looking a little weird, with the rubber bushing (black) located out near the hooked end of the bar.
A-ha! This single top link (white) connects the middle of the rear-end housing to the unibody. Together with a matched pair of the trailing links we saw before, we can see why Ford calls this a three-link solid rear axle.
But these three links can only control the fore-aft and torque movement of the rear axle. They can do nothing to resist lateral loads. For that there's a Panhard rod (yellow).
Before we look at that in more detail, let's talk about the rear-end housing and what's inside it. The 3.73 diff ratio found in a GT500 with the SVT performance package, like this one, is NOT intended to enhance performance over the 3.55 ratio found in a regular GT500.
It's like this: the standard GT500 wears P285/35R19 rear tires, while the SVT track package comes with taller P285/35R20 rear meats. Turns out the 3.73 ratio is primarily intended to offset the performance-robbing taller gearing created by the taller 20-inch tires, and the two setups end up at more or less the same place from the engine's point of view. In other words, a GT500 with the SVT performance pack will turn over about the same number of revs as a regular GT500 at a given gear and engine speed, despite the impressive-looking difference in final-drive ratios.
That said, the 3.55/3.73 ratios offered on the GT500 are indeed more performance-oriented than the 3.31 gears offered on the Mustang GT and V6.
A Panhard rod (white) connects to the unibody on one end and the axle housing on the other end. You want it to be as long as possible so its "swing radius" is long enough to minimize the amount the axle moves left-to-right as it moves up and down.
Meanwhile, the rear-stabilizer bar mounting strategy is a bit unusual. Bass-ackwards, I would say because the links (green) are the pivots and the bushings (yellow) affix the ends of the bar. Hey, it still works. It's actually an effective way to put a rear bar on a solid live-axle car.
Once again, the GT500 uses one of the bars fitted to regular Mustangs, but in this case it's the larger 24mm bar from the GT. Together with the smaller bar on the front, this combination, on paper, at least, will produce the least amount of understeer. But that doesn't necessarily make the GT500 more tail-happy because the GT500 is the only variant in the Mustang stable that has wider rear tires than it has at the front. Taken as a whole, it all fits together.
Let's move back to the Panhard rod for a bit. The fixed end is this protruding bracket (green, no blue) that's welded firmly to the unibody itself. The upper piece (white) is a bolt-on stiffener that spans across the car to help stiffen the bracket near the point where the lateral loads will be applied by the panhard bar (yellow) itself. After all, the approximate loading will work out to whatever the rear tires can generate on a skidpad times the weight of the rear half of the car.
The other end of the Panhard rod (green) mounts to this bracket on the left end of the rear axle housing. It's a busy place, as evidenced brackets for the shock, that stabilizer bar end bushing (yellow), the trailing link (white) and even a rust-colored mass-damper.
About those trailing links: Despite what you may have assumed earlier, they're not made of aluminum. As you can see here (yellow), they're made of two pieces of stamped steel that are welded together. Let's hope the choice of silver as a paint color wasn't intentionally made to make the casual observer believe these are lightweight aluminum bits.
The SVT performance package includes rear springs that are 9.5% stiffer while they lower the rear of the car 8mm relative to a regular GT500. A urethane bump stop sits atop the axle next to each coil spring. When the suspension bottoms, it will impact a nearby reinforced part of the body structure and cushion the blow.
Red is the "in" color for GT500 rear shocks. These SVT performance pack units have higher damping levels that are tuned to work with the stiffer springs, lower ride height, stickier tires and other bits and pieces that come with this GT500 option.
No Brembos back here. The GT500 uses single-piston sliding calipers and ventilated cast-iron rear rotors, just like other Mustangs. Not that there's anything wrong with that.
These sticky tires are a big part of the SVT performance package, literally and figuratively. Size-wise, they're huge compared to other Mustang tires. How does P265/40R19 front and P285/35R20 rear grab you?
GT500 tires come mounted on lightweight forged aluminum rims, so their mounted weight, at 62.5 pounds apiece front and rear, is respectable for rubber this size.
You'll never have to (or be able to) rotate these babies left to right because the tread pattern is directional. In case you were wondering, the right half is the outer surface and the big directional water channels reside on the inner surface. Don't recognize the pattern? It's new. These are Goodyear Eagle F1 SuperCar G: 2 tires.
Goodyear chose to put that awkward space between the colon and the "2" in the official model name of this tire. My hands are tied.
So what makes a GT500 so different from a Mustang? Well, there certainly are differences in the wheel wells, but nothing too revolutionary. No, the most significant GT500 difference is under the hood in the form of a 550-horsepower supercharged V8 engine.