Steeda's G-Trac Street Suspension - Proper Snake Handling
Getting A Firm Grip With An IRS Cobra Thanks To Steeda's G-Trac Suspension.
From the February, 2009 issue of Muscle Mustangs & Fast Fords
By Vinnie The Hitman
Photography by Frank Cicerale, Michael Galimi, Vinnie The Hitman
Getting funky with our Cobra...
Getting funky with our Cobra is easy with our new Steeda suspension.
When Ford announced that its top Mustang, the SVT Cobra, would get a genuine IRS rear suspension in 1999, the news sent shockwaves throughout the automotive community. While drag racers winced and immediately figured out ways to retrofit a solid-axle 8.8 underneath, autocrossers and open-track fiends finally had their prayers answered with a suspension package that featured robust aluminum lower control arms, forged steel uppers, and adjustable toe links, all wrapped around an aluminum differential that used conventional 8.8 gears. It was a match made in heaven. Well, at least on paper.
When we took our first turn behind the wheel of a pre-production car back in late 1998, we ran it through its paces and it didn't take long to realize something was amiss. Aside from noticeable wheelhop, we quickly concluded that the IRS was lacking in response, predictability, and more importantly, traction, while applying power in a turn. After a few '99 Cobras fell into the hands of several twisty turney racers, the same conclusion was quickly made.
Luckily, Ford heard the cry and in 2003, coinciding with the launch of the much-more-powerful Terminator, it beefed up the IRS. Aside from larger 31-spline axleshafts, the biggest change was the addition of specific rate springs and aggressively tuned Bilstein shocks to control wheel movement. Going up to 17x9 wheels and 275/40/17 tires also helped, but its inherent design was still flawed. Despite the changes that Ford made, it still didn't feel right as the car felt somewhat disconnected when driven hard.
Fast forward to 2008, and we've witnessed a huge step in making IRS Cobras finally work. There are a few companies making suspension components for the '99-'04 IRS Cobras, but based on our experience, few have put together a kit that is comfortable enough for the daily grind, yet competent enough for the track, as well as Steeda has. Now we all know that Steeda is no newcomer to the Mustang suspension market, but when it comes to manufacturing its own suspension upgrades, going to Steeda is like coming home, as you know that you'll get OEM-type fit, finish, and quality.
Getting On Stage
For '03-'04 Cobras, Steeda offers three different G-Trac suspension systems-Street, Competition, and Drag. Since we wanted a more aggressive ride without excessive harshness, we kept things realistic and chose not to put a full-blown competition suspension into our Snake, as it was simply overkill for our weekend play toy. In addition, with our focus on handling, we found no need to go with a dedicated drag suspension because this car has already been running strong with a best of an 11.92 at 118.9 mph.
So, of these three choices, we went with the Street kit, which has components bundled into four complementing stages that allow a Cobra owner to install each stage separately. For instance, you can start with Stage 1, and then add Stage 2 and Stage 3 later. Then if you wanted to, you could finally put Stage 4 in the car a few months down the road. Or you can order all four stages at once, and a complete suspension upgrade can be performed at one sitting, which is how we did it simply because of deadline restrictions.
Starting with Stage 1 (PN 555-2155), we stiffened up our ride with Steeda's boxed steel subframe connectors, three-point tubular steed strut tower brace, billet aluminum caster/camber plates, and Sport Springs, which lower the car a little over an inch. This is often where many people start and serves as the "gateway drug" to better handling and fun on the street.
We then stepped up to Stage 2 (PN 555-2156), which features Steeda's polyurethane IRS subframe and differential bushings, steering rack bushings, heavy-duty antisway bar endlinks, front sway bar bushings, and superfly billet sway bar mounting brackets. For the upper rear subframe mounts, the included reinforcement kit will eliminate a lot of flex that goes on back there.
Steeda offers its G-Trac Street...
Steeda offers its G-Trac Street suspension in four stages for the '03-'04 Cobra. We decided to install all the stages at once because if we're going underneath the car, we want to do it only once. Here, we see the all-important chassis-stiffening subframe connectors (weld-in) and strut tower brace.
For our testing purposes,...
For our testing purposes, we went with a set of 18x9.5 Steeda Pentars with a set of Nitto INVO tires spooned on them. We installed the new rolling stock to baseline the car before we upgraded the suspension. We also used a set of NT-555s on the stock 17-inch Cobra wheels. Our baseline was set at 1:24.77.
For the front suspension,...
For the front suspension, Steeda supplies its Sport Springs, which lower the car slightly over an inch, and include billet aluminum caster/camber plates, offset lower control arm bushings, and bumpsteer-quelling outer tie rod endlinks. Note how the Bilstein struts are an inverted style, which allows a much larger strut shaft to telescope in and out of the housing. This makes for a much more rigid design than your typical Motorcraft piece that will not flex as an assembly under heaving, braking, or cornering.
Out back, Steeda addresses...
Out back, Steeda addresses some of the key weaknesses of the IRS. Aside from adding polyurethane bushings to the upper and lower control arm pivots, it also adds stiffness to the entire subframe assembly at all of its attachment points. High-capacity Bilstein shocks and Steeda's Sport Springs bring everything under control.
To start things off, remove...
To start things off, remove the brake caliper with a 15mm socket and slide off the brake rotor. Next, undo the spindle nut with a 15/16-inch (24mm) wrench, but do not remove it. Using a large hammer, whack the spindle to free this joint, taking advantage of the spring pressure to help pull it apart. Once it is free, remove the ABS sensor with a 1/4-inch six-point socket, and remove the ABS sensor wire's bracket with a 24mm socket. Then, remove the two lower strut housing nuts with the same socket, but leave the bolts in place.
Remove the steering rack with...
Remove the steering rack with a 15mm socket from behind to hold the bolts and grab an 18mm socket to remove the front nuts. Undo the outer tie-rod ends from the spindle by removing the Cotter pins and castle nut with a 19mm wrench. Free the tie-rod end, disconnect the steering shaft, and slide the rack forward, keeping an eye on the two power steering lines. Now, place a jack underneath the lower control arm on the inboard side and remove the lower control arm bolts with a 24mm socket for the nut and a 21mm socket for the bolt head. The front bolt will slide forward and the rear bolt will slide backwards, but you may need to remove the outboard crossmember bolt with a 15mm socket in order for it to slide out. Lower the jack slowly to relieve the spring pressure.
Also included are Steeda's innovative anti-bumpsteer kit (which relocates the pivot point of the outer tie rod so that toe angle does not change during compression of the front suspension) and Steeda's trick X2 lower ball joints. Now, you may be wondering what role a lower ball joint has in improving handling, but it's pretty cool how the X2 piece works. With the stock ball joint, control arms can pivot too far up into the car and track width, camber angle, and even the toe changes, which can make handling quite unpredictable. By extending the shank portion of the ball joint (like the X2 does), though, the outer ends of the control arms sit further down and make the arms themselves sit more parallel to the road, allowing them to work within its original range of motion for improved suspension response and proper geometry. Appropriate spring spacers are included to compensate for the vehicle height that would have been lost if one installed the X2 ball joints alone.
Moving up to Stage 3, PN 555-2157, you'll benefit from world-class Bilstein dampers all around, which are an improvement to even the original Bilsteins that came from the factory on all '03-'04 Cobras. Next up is Steeda's own lower G-Trac brace that ties the rear of the front crossmember together for improved rigidity. It should be noted that a lower brace was installed at the factory, but the Ford piece is a stamped steel unit that is crush-bent and does not offer as much reinforcement as the Steeda piece, which is a straight tubular steel bar. Lastly, Steeda's innovative 1.375-inch tubular front antisway bar with spacer kit rounds out this stage.
Once you're at Stage 4, you've reached Steeda's pinnacle for street-ready IRS Cobra competence. To complete Steeda's suspension upgrade for Terminator Cobras, PN 555-2158 includes a steel IRS differential cover brace, polyurethane bushings for the rear control arms, and offset front control arm bushings for more caster and subsequently, more camber gain as the wheel is turned. Lastly, a solid steering shaft, supplied by Flaming River, tightens up steering response at the wheel and provides more immediate feedback to the driver.
Not wanting to leave all of our mods on a set of worn tires, we chose to upsize with 18-inch shoes. Since we were on a street theme, rather than a track-only setup, we elected to go with Steeda's own Pentar wheel in 18x9.5-inch sizing, wrapped in Nitto's grippy INVO tires, measuring 275/35/18 all around. These rather new tires are designed for high-end exotic cars, so we felt confident they would be perfect for our top Snake.
As installation was a simple R&R, not too many special tricks were required. We were able to do everything in our own home garage with a generous selection of mechanics tools and plenty of patience. It should be noted that suspension service can be dangerous for the inexperienced mechanic, and we recommend having someone who knows their way around the underpinnings of a Mustang to be by your side. Sadly, I've done nothing but resurrect rotten old Fox and SN-95 Mustangs from the brink of extinction for the past 15 years, so I'm a rather experienced Mustang suspension meck-a-nik, which can be fortunate for this story (or unfortunate, depending on how you look at it).
To catapult this Cobra around Raceway Park's road course (in its shorter configuration) we relied on the driving services of Chris Winter, the manager of the track and owner of Crazy Horse Racing. Aside from being able to give us repeatable numbers, his experience on this track with Mustangs would be very valuable. He also gave us candid feedback on how the suspension performed both before and after the Steeda components (for detailed driving impressions, see sidebar).
With the lower control arm...
With the lower control arm and spindle separated from the strut housing, go ahead and use a 15mm socket to remove the two nuts and one bolt that holds the factory strut plates to the strut towers. Then, drill out the two aluminum pop rivets with a 3/16-inch drill bit and remove the strut from underneath.
Install the Steeda caster/camber...
Install the Steeda caster/camber plate onto the strut tower and tighten down the bolts with a 9/16-inch socket. Slide the strut mount all the way backward for maximum caster, and tighten down the three bolts with an 8mm Allen key.
It's time to prep the lower...
It's time to prep the lower control arms. Using a ball joint press, remove the original and install the new Steeda X2 units. You'll note how much longer the tapered shank is on the X2 as it promotes proper control arm geometry on lowered cars. It is a direct replacement.
Remove the original control...
Remove the original control arm bushings with a hydraulic press and install the new ones by Steeda. Using the same ball joint press from before, you can press the new ones in as they are complete units with the outer shells.
With the factory bumpstop...
With the factory bumpstop and dustboot transferred to the new Bilstein strut, slide it into place and install the hardware from above to attach it to the caster/camber plate.
With the antisway bar removed,...
With the antisway bar removed, we can see how much nicer the larger 1.375-inch tubular Steeda unit looks in comparison to the 1.125-inch original. Steeda's hefty billet aluminum mounts for the antisway bar replace the flex-prone stamped steel units and do wonders to improve transitional handling. It is important to note that on an '03-'04 Cobra like ours, an additional spacer kit (PN 555-8124) is required to properly clear the engine oil cooler.
We baselined our Cobra with a 1:24.77 lap time and were able to pound down some rather strong and consistent supporting numbers. Due to our Cobra's relatively weak factory-stock cooling system, we were able to only get four laps before the engine management system began taking timing and rpm out from the excessive engine temp.
A few weeks later, we went back armed with our new suspension. Using the exact same tire pressures, track configuration, and driver, we'd be able to see exactly how much better our car would handle.
After one warm up lap, Chris dove into the Cobra's deep torque curve and quickly applied the power from turn to turn, posting three times that were eerily consistent: 1:18.92, 1:18.55, and 1:18:03, all of which were improving as he went along. Like last time, the engine began running too hot for the EEC-V's comfort, and any throttle input resulted in a rev limiter that sounded like the traction control was on in the burnout box. Despite laying down just four laps, we were able to record a solid 6.74-second improvement.
Like in drag racing, having nearly seven seconds shaved off your time on a road course that is over a minute long is like an eternity. As Chris mentioned, "The suspension is night and day. It gets more power to the ground in the turns and relies on the tires for more grip, whereas the stock suspension gave up before the tires did. Put an R-compound tire on this car and you're talking serious numbers."
Afterwards, I then strapped myself into the car to see what he was talking about. Without a doubt, he hit everything right on the head. When the car was stock, it felt top-heavy and wallowed. Also, in slower turns, the rear always felt disconnected, as the inside wheel would never put the power down, no matter how hard the 8.8's diff tried.
With the Steeda suspension, however, the rear stayed planted under power, and more impressively, would rotate slightly under deceleration in a turn. In higher-speed sweeping turns, the car was much more stable, eliminating the stock suspension's tendency to gyrate under full acceleration.
Getting power from a Terminator is so easy most people don't need to spend more than a few hours of wrench-turning to make 500 hp. But getting that power to the ground on the street, well, that's a whole other part of the equation. Sure, one can build an 1,100 rwhp car for the dyno and spin tires in Fifth gear for Internet junkies to watch online, but we'd rather have our 453 rwhp and use every one of them everywhere we go. Thanks to Steeda, we now can.
For our track test, we relied on the capable hands of Chris Winter to drive our Cobra test vehicle. If his name sounds familiar, it's because he's popped up several times in our magazine as the proprietor of Crazy Horse Racing in South Amboy, New Jersey. When not busy running his Dynojet, he spends his time at Raceway Park's road course managing its layout and accommodating the needs of all racers. In his free time, he's an avid road race junkie that instructs for the PDA, the Performance Drivers Association (www.pdadrivingschool.com).
So with our Cobra in his capable hands, Chris gave us the skinny on how the car fared with both the stock suspension and the 18-inch Nitto INVO tires compared to the NT-555 tires that were mounted on the stock Cobra wheels. When the car was stock, he complained about the amount of slop and how impossible it was to apply power anywhere in a turn. In transitions, the stock suspension was not liking it, as side-to-side weight transfer was quite pronounced. As for the tires, he mentioned that the NT-555 tires made the Cobra have more understeer, but the INVOs transformed the predictability of the car as it had a more approachable limit. Once at that limit, the tires did not bite you back if you were in a slide. Interestingly, Winter was quicker on the smaller NT-555s, which are more competition bred with its 260 treadwear.
The lower G-Trac brace replaces...
The lower G-Trac brace replaces the factory stamped steel unit and simply bolts into the existing holes. Just be mindful of bellhousing clearance as it does get tight. On our car, it cleared with just 0.050-inch to spare.
Steeda's bumpsteer elimination...
Steeda's bumpsteer elimination kit replaces the original outer tie rod with a Heim joint and stackable spacers that can lower the pivot point to get rid of, you guessed it, bumpsteer. If you hit a bump mid-corner, suspension compression may cause your tie rod angle to drastically differ from your lower control arm's angle, effectively changing the toe on that side of the vehicle. This will cause the car to jerk to the side and the results can suck the upholstery right from under you. Thankfully, this eliminates that feeling.
A sturdy Flaming River steering...
A sturdy Flaming River steering shaft replaces the original and transmits newfound precision to your fingertips. It takes a few steps to assemble, but the results are worth it as this direct-fit part does away with that sensation-numbing rubber coupler from Ford.
With our suspension back together...
With our suspension back together underneath, we lined up the strut tower brace with enough clearance under the supercharger to take into consideration engine movement. We then drilled a few holes to mount the brace to the strut towers. At the rear, you will have to remove the wiper arms and cowl cover to reach behind the firewall to fasten the brace for full triangulation of the engine compartment.
To get enough access to all...
To get enough access to all the bushings that get upgraded to polyurethane, the entire rear suspension subframe must be lowered a few inches out of the car. With the exhaust system and driveshaft removed, we placed a jack under each control arm to remove the lower shock absorber bolts with an 18mm socket. Then, with the jack under the rear differential, the crossmember support bolts were removed with the same size socket, and everything was slowly lowered.
We started things off by replacing...
We started things off by replacing the rear subframe bushings. Since you'll have to reuse the existing steel outer shells, carefully remove the original insert by drilling a bunch of holes through the rubber and use a ball joint press to push it out. The new polyurethane bushing then gets lathered in grease and is pressed into its new home. We had to do the same for the forward subframe bushings, and of course, the control arm bushings as well.
To access the upper shock...
To access the upper shock absorber mounting nuts, remove all the inner trunk panels, and using a 15mm socket, remove the nuts and pull the struts out from underneath. Then, slide the new Bilsteins from underneath, and while a friend is holding it in place, start the new nut onto its threads. Here, you'll have to hold the shaft in place with an 8mm wrench and tighten the retaining nut with a larger 17mm wrench. Go until the bushings start to bulge as shown.
As you raise and re-install...
As you raise and re-install the entire rear subframe, place the rear springs in place, making sure to clock them in the same position as the original ones for a consistent ride height from side to side. Reusing the rubber isolators is highly recommended for proper ride height and reduced road noise.
With the entire subframe back...
With the entire subframe back in place, jack each control arm up to compress the spring and re-install the lower shock bolt.
With the full Steeda suspension in place (G-Trac Street, Stages 1 through 4), we let Winter back on the track, and as expected, he was 6.74 seconds quicker using the NT-555 tires. The drastic time drop was easy to see as the car simply hooked and went. As he states, "In certain areas, I was as much as 15 mph faster because I was able to plant the power fully and earlier in the turns without the car being unstable. That made the biggest difference, in addition to the flatter cornering in the faster turns."
Our subsequent follow-up drive on the road course backed his comments and reinforced our belief in leaving track driving for the track. But later, the ultimate test was on the street where we could see how it was to live with the new suspension. The ride is slightly stiffer than before. We'd say the ride is about 10-15 percent firmer. The car now has a more aggressive stance that not only looks the part, but also acts the part with incredible stability on the highways and byways.
In case you were wondering,...
In case you were wondering, this is how our Cobra took turns when it was stock. As you can see, the already-high ride height didn't help the car in turns as it leaned heavily, placing most of the weight on the outside front tire and almost lifting the inside rear tire. This explains why it is so hard to throttle out of a sharp turn in a stock Cobra, even when you're using sticky rubber. Despite this, Chris Winter, our hired driver for the day, was able to muster a respectable 1:24.77 lap time.
Since we were able to only...
Since we were able to only get about four laps before the Cobra started to run hot and shut down under throttle, we had plenty of time to admire our Dark Shadow Gray SVT Coupe in the pits. Note how silly the stock ride height looks, especially in back. Those Steeda Pentars sure look purdy, don't they? We used the Nitto INVOs here, but found the more-aggressive NT-555s to provide the best lap times despite the more pronounced understeer.
With our new suspension in...
With our new suspension in place, you can see how more composed the car is in the turns. In fact, we could induce throttle oversteer, which is nice. The INVOs made the car more predictable as understeer was no longer obvious. We were now 6.74 seconds quicker with a best lap of 1:18.03. If we had more engine cooling, we could have been able to whittle it down into the 1:17s.