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Suspension Upgrade - Project Redheaded Step Child Part 5
Project RSC gets maximized with a new suspension, wheels, and tires.
There I was, driving home from a successful three-day adventure with the guys at Maximum Motorsports, minding my own business, when all hell nearly broke loose. I was tooling along with the cruise control thankfully set at 70 mph (a serious CHP presence had prohibited running any faster) preparing for the upcoming on ramp that merged the 101 freeway onto the 405 S.
Having just stopped for fuel, I took the liberty of supersizing myself at the local golden arches. French fries and McNuggets (come on-they're suppose to be white meat) are certainly traveling food, but only with proper preparation. I reengaged the freeway only after securing my bladder-buster-size beverage in the appropriate beverage containment system, the fries within easy reach.
I merged over to the far right (slow) lane in preparation for the freeway junction, switching off the cruise control and dropping into Fourth gear in anticipation of the slower traffic that invariably accompanies any type of turn. Seemingly out of nowhere, some punk in a BMW 3-series made the proverbial big move, positioning himself right in front of me, which forced me to take emergency evacuation maneuvers. I came this close to spitting out my fries and dropping my McNugget.
This set off a chain reaction, the likes of which had me, Mr. BMW, an Explorer, and a Celica performing all kinds of unnatural acts on a public road. With seemingly inches to spare (probably more like yards), I missed clipping both the front of the Explorer and the rear of the Celica and "safely" merged into the left lane and then onto the 405 freeway. To my surprise, everyone on the 405 seemed to be driving considerably slower. Glancing down at my speedo, I realized it wasn't so much that they were going slow as I was going fast-triple-digit, throw-you-in-jail kind of fast.
The stability of the Mustang during this exercise was rock solid, providing me both the confidence and grip to not only motor around the offramp (at ludicrous speed) but to safely make evasive maneuvers. It was this encounter from which I drew a scientific conclusion: This suspension kicks ass!
Normally, I would strive to provide real-world, back-to-back data generated through extensive testing when performing such an elaborate, and effective, suspension upgrade. Unfortunately, only Editor Jim Campisano and Tech Editor Evan Smith get to rent dragstrips and participate in scheduled track days at the MM&FF Road Course, leaving the West Coast Redheaded Stepchildren (both author and vehicle) to fend for themselves (it sucks being a latchkey contributing editor).
While lap times before and after the suspension upgrade might provide some measure of the handling improvements offered by any suspension upgrade, the vast majority of Mustang owners do not frequent road courses. Like mine, their adventures are confined to frontage roads, freeway offramps, or their own special mountainous test route. While Project RSC may well see some open track action down the line, it is first and foremost a daily driven street car. The suspension upgrades were chosen with this in mind, as there were certainly changes to be made to our upgrade choices to further improve ultimate lateral acceleration. But we are now at a level that the changes require compromises to both ride quality and tire wear.
Maximum Motorsports does offer complete suspension systems capable of winning on the track (the company's achievements in the American Iron series attest to this fact), but solid bushings, motor mounts, and 3.5 degrees of negative camber are not what we would consider street friendly. Know that if you decide to go that direction, Maximum Motorsports has you covered, just as it did with our maximum performance street suspension.
Though ride quality was an important consideration for our daily driver, so too were improvements in handling. Wanting a serious canyon carver, we put our requirements to the experts at Maximum Motorsports, who suggested its Maximum Grip Box. This is the most complete system offered by the company, and it is employed by many successful Mustang racers. By selecting the correct combination of shock/strut valving and spring rates, we were able to tailor the Maximum Grip Box to suit our needs.
The extensive component list included front and rear coilover conversion kits, Bilstein sport shocks and struts, a tubular K-member and brace, a rear Panhard bar system, a torque arm, tubular front and rear control arms, full-length subframe connectors, camber/caster plates, adjustable tie-rod ends, aluminum rack bushings, a solid steering shaft, an adjustable rear swaybar, urethane swaybar bushings and endlinks, and a front strut tower brace (which we did not use).
Installation of all the individual components in the Maximum Grip box is much more involved than your usual shock, spring, and swaybar swap, but the handling improvements are definitely commensurate with the effort. If you only want to dump your Stang in the weeds, then you can save money by just cutting your stock springs. It's going to handle like crap, but at least it will be lowered. If, however, you're looking for a serious G machine, go with the Maximum Grip Box.
What I liked best about the Maximum Motorsports approach is that it came from a racing background. Being a road racer at heart, I appreciate what it takes to make suspension components work in this harsh environment. Designing and building components is just one phase, something that should be followed by actually testing them on the track under race conditions. The finest tools are forged from the furnace of competition. While the MM guys subject their suspension components to the rigors of the racetrack, they also took the next step by building a test fixture that allowed them to visualize (measure and document) the deflection caused by suspension loads. This fixture (basically the rear section of a Mustang flipped upside down) illustrated the binding issues inherent in the factory four-link rear suspension, and that urethane bushings at both ends of the control arms often aggravated this binding by not allowing angular motion of the upper arms (something provided to some extent by the deflection of the softer rubber bushings). This testing produced a rear suspension that eliminated the binding inherent in the four-link design.
There's a lot to like about the Maximum Grip Box, but the attention to detail sets one system apart from the rest. The first components installed on Project RSC were the MM subframe connectors, which were full length and even featured provisions to tie in the seat mounting bolts. What we liked about these connectors was that the seat braces were not connected to the main braces, and were instead welded in place after welding on the connectors. There is nothing more frustrating that having to wrestle with getting the seat-mount bolt holes to line up while properly positioning the connectors on the frame. Being able to weld them in after the fact allows for the production tolerances inherent in the shape of the floor as well as distortion that can occur from jacking up the car incorrectly. We also liked that the bend in the connector necessary to contour the shape of the floor was triangulated by welding a plate over the top, adding even more strength to the connector system. The connectors were powdercoated black, requiring only minor touch-up (with black spray paint) to the welded areas.
After measuring the stock ride height, the rear suspension was disassembled to make way for the MM torque arm and Panhard bar systems. The rear suspension also included replacing the quad-shock factory setup with a coilover assembly featuring Bilstein shocks and Hypercoil springs. Given our street orientation, we decided on sport shock valving to work in conjunction with the 250-pound rear spring rates. The coilover system offered a weight savings over the individual quad shock and spring combination, allowed adjustments in ride height, and provided the ability to corner weight the car to maximize handling.
The coilover kits were designed to maximize bump travel-critical in a lowered Stang-and featured hard anodizing (not just a cosmetic coating) and a tight fit between the threaded sleeves and shock/strut bodies. This precision fit ensured that the lower spring perch remained square to the strut or shock, thus preventing the spring from arcing and rubbing on the sleeve. On the front coilover assemblies, O-ring seals were applied to seal the thrust bearings from dirt and water. The MM rear coilovers also featured bumpstops to replace the factory (rear-axle mounted) units.
The rear suspension also received a set of new tubular lower control arms. The lower arms featured urethane bushings for the chassis end and a spherical rod end for the axle end. Since the suspension was being converted to a torque-arm setup, we ditched the factory upper control arms.
According to Maximum Motorsports, differing the bushings used in each end of the control arm is critical for proper operation. Since the control arms (both upper and lower) do not move in a direct up and down pattern (they prescribe an arc), side movement must be allowed. With the stock bushings, this angular movement is provided by deflection in the bushings.
Unfortunately, these soft rubber bushings also allow fore and aft movement, which offers minimal control over axle wind-up. Many tuners opt for urethane bushings at both ends in an effort to control the bushing deflection, but MM feels this also minimizes the angular movement. The use of urethane bushings on both ends can actually decrease handling as the system is much more likely to experience bind. Once bound, the deflection comes from the sheetmetal surrounding the mount-not a good situation. By combining a spherical bearing on one end and urethane on the other, all the fore and aft deflection is eliminated while allowing the arms to travel freely through their natural arc.
With the removal of the upper rear control arms, it was necessary to control side-to-side movement of the rear axle. This was accom-plished with a Panhard bar. Just as the factory rubber bushings allow deflection that can cause axle wind-up under hard acceleration, this same bushing deflection can create havoc under lateral acceleration by allowing side-to-side movement of the rear axle. Naturally, you want the rear axle to stay positively located under hard cornering, something the Panhard bar does much better than the factory four-link since the bar is located in line with the cornering loads, where the factory upper control arms are mounted at a 45-degree angle. Ideally, the Panhard bar should be as long as possible and mounted level to the ground. The MM Panhard bar setup is adjustable to keep the bar parallel to the ground at a variety of different ride heights.
The MM bar also measures 38 inches in length, thereby minimizing the amount of rear axle movement associated with the arc of the rod's movement. Unlike some systems, the MM Panhard bar can be used with factory and aftermarket exhaust systems that maintain the factory routing. One feature I liked was the use of frame inserts to eliminate collapsing the rear subframe mounting points.
Before finishing off the rear suspension with the torque arm and adjustable rear swaybar, the gang at Maximum Motorsports turned their atten-tion to the K-member, front tubular control arms, and coilover assemblies. They made quick work of removing the factory front suspension compo-nents, including the heavy K-member. Compared to the factory unit, the MM tubular K-member offered a weight savings of 14 pounds.
In truth, I was less concerned about saving a few extra pounds than having the strength required to take the new suspension loads. Back in my road racing days, I experimented with a lightweight tubular K-member on our World Challenge car, only to find out that while it may have been OK for drag racing, the flimsy unit required extensive structural surgery before it could withstand the punishment of road racing. The Maximum piece is ready to go road racing without mods.
It was equally important that the MM piece offered both an increase in wheelbase of 3/4 inch (thereby improving the weight distribution) and optimized vertical location of the control arm pivot points. The ideal mounting location (and therefore angle of the control arms relative to the ground) changes with the desired ride height. Dual pickup points on the K-member provide alternate mounting locations to keep the arms parallel to the ground, offering both an improved camber curve and roll center height.
Unlike many of the aftermarket tubular control arms available, the pair from Maximum Motorsports were a true A-arm design, offering a brace between the V shape produced by the pair of tubes converging from the pickup points to the ball joint. This cross brace adds a great deal of strength to the design, minimizing deflection. Like the tubular K-member, the control arms offer significant weight savings, in this case, over 13 pounds. Though MM offers offset control arms that provide an increase in wheelbase of 3/4 inch (making a total of 1 1/2 inches when combined with the K-member), we opted once again for the more street-oriented standard offset arms.
When combining the offset arms with the K-member, it is sometimes necessary to modify the fenderwell to accept the forward position of the wheel/tire package. Not wanting to modify the fender lip, we chose the standard arms.
The tubular control arms required the use of coilovers, so MM supplied its front system consisting of Bilstein struts (with sport valving) combined with 375-pound coil springs. For race applications, spring rates over 400 pounds might be applied along with race valving in the struts, but once again, this street application requires appropriate spring rates and shock valving.
Other modifications to the front suspension included new urethane mount bushings and endlinks for the factory front swaybar, a set of aluminum steering rack bushings, and adjustable tie-rod ends. The urethane mount bushings and endlinks improved the response rate of the factory tubular front swaybar, while the aluminum steering-rack bushings eliminated any bushing deflection to greatly improve steering response.
The real change to the steering came from the adjustable tie-rod ends, which allowed us to adjust the bumpsteer (changes in toe as the suspension moves up and down). Changes in the amount of bumpsteer present were made by altering the number of spacers between the tie-rod end and the spindle. Once dialed in, the bumpsteer was minimized to just 0.020 per inch of suspension travel-pretty good for a strut front suspension. Nice touches on the adjustable endlinks included the machining of a hex at the inboard end (to facilitate adjustment), a wide assortment of high-alloy steel spacers, and two pairs of different length bolts to ensure proper fitment of the necessary spacer arrangement. It was necessary to drill out both spindles to accept the through bolt, but MM also offers adjustable tie-rod kits to work with the stock (tapered stud) spindle, though this combination is limited to moderate changes in geometry.
While the K-member was off, we replaced the factory steering shaft with a solid version to further improve steering response, which also eliminated an annoying interference problem between the factory shaft and the Hooker headers.
After taking the measurements (the positioning is critical), the K-member was bolted in place along with the remainder of the front suspension components. After the front was completed, the MM guys went back to the rear to install the torque arm and adjustable rear swaybar, though like the front, the endlinks were not attached until after it was time to scale the car. Since we have big plans in the powerplant department, we decided it was prudent to go with the heavy-duty torque arm. The torque arm required suitably strong (weld-in) subframe connectors, proper lower control arms (that resisted binding), and a sturdy Panhard bar-all of which were part of the Maximum Grip Box but must be used if installing the torque arm on a Mustang equipped with other brand suspension components.
According to MM, we could expect a dramatic improvement in traction, both leaving the line and exiting a corner, thanks to replacing the bind-prone, four-link factory rear suspension with the torque-arm-enhanced three-link.
Combined with the Panhard bar, the torque arm eliminates the upper control arm attempting to perform double duty (controlling axle wind-up and locating the rear axle), something they fail at on both counts. The torque arm is positioned to eliminate axle wind-up, leaving lateral control up to the Panhard bar. The trick to installing the torque arm was to measure and adjust the pinion angle (using the supplied shims) before bolting the arm to the rear differential. The rear swaybar was the last component to be installed-the welding made easy thanks to the supplied orientation plates that properly located the (weld-in) mounts.
After the rear swaybar was successfully installed, it was time for alignment. Since the goal of any suspension upgrade is to improve the contact patch between the tire and road surface, the alignment specs are critical. Were we attempting to maximize the handling for the track, we might get aggressive on the alignment specs, jacking maximum caster and as much as 3.5 degrees of negative camber (with just a hint of toe out), but these specs would quickly ruin a set of tires (or at least the inside edges) on the street. For the street, the MM gang dialed in the alignment specs at 3/4 degree negative camber, nearly 7 degrees of caster, and 2 mm total (1 mm per side) toe in. On the scale (corner weight scales), the '96 GT checked in with a total weight of 3,562 pounds with driver and full of fuel, offering a front-to-rear spilt of 55.6 percent (front) and 44.2 percent (rear). The diagonal readings (LR to RF and RR to LF) were dialed in (by adjusting the ride height slightly) to achieve a near-perfect balance of 49.7/50.2 percent. After hooking up both swaybar endlinks, Project RSC was officially Maximized.
We didn't have to take the car more than 10 feet to recognize the improvement. A quick drive on the official MM test loop revealed the new suspension had literally transformed the Mustang. Where the (well-aged) stock suspension seemed to provide no other benefit than keeping the body from rubbing the ground (but not equally front to rear), the Grip Box made the car feel whole again. Gone was the feeling of having the front and rear suspensions arm wrestling to see which would lose grip first, replaced by unity, solidarity, and coopera-tion between the two ends. The Mustang now felt secure and confidence-inspiring, allowing balanced four-wheel drifts (though at a much higher speed).
Where the stock suspension was limiting the tire adhesion, the reverse was now true with the Grip Box. The generic tires were now limiting the effectiveness of the suspension. The tires give up just as the suspension is getting started-a situation we cured with a set of Nitto 555 18-inch tires and Ford Racing Cobra R rims (9.5 inches wide). Now, we can finally enjoy driving the Mustang thanks to the newfound grip. Our only complaint is that the new suspension makes the 240 hp feel terribly inadequate.