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How To Install the Ultimate Fox-Body Suspension - Turn And Burn
Maximum Motorsports helps us cut 1.39 60-ft’s and pull 1.06 g’s of grip with one suspension
They said it couldn’t be done, that an old Fox-body Mustang could never handle like a sports car and still kill the dragstrip. The naysayers said we’d never build a smog-legal Fox-body that could run with a GT500 at the strip and hang with a Boss 302 in the corners. But after countless hours spent wrenching, many late into the night, a few broken parts at the track, blood, sweat and tears, we proved them wrong.
After our semi-fruitful trip to the track on the four-link setup that used drag shocks and springs as well as a rear ARB, we parked the car and left scratching our heads. We ran 10.80s, but the trap speed was far too low for the weight and power levels. A loose exhaust header necessitated we remove the charge pipe before the next track outing. As luck would have it, the culprit was found. A loose air-bypass valve that was bleeding boost after the MAF, causing our 9.0:1 AFRs and the low trap speeds.
Call it fate or maybe just dumb luck, but about that same time we received a call from the engineers at Maximum Motorsports (MM) about a separate story, and during that conversation we couldn’t help but ask them about our pie-in-the-sky goals with the Smog-Legal Killer. We wanted to stay in the 10s at the strip and pull over 1G on the skidpad with only one suspension setup. The only changes between the strip and the road course could be ride-height/shock settings and a wheel/tire change. Expecting silence in return, our jaws dropped when Jack Hidley, a senior engineer at MM, told us it was possible with the company’s Maximum Grip Box. Say it ain’t so! Could we really build an all-around Fox-body that excelled at everything? As it turns out, quite easily thanks to Maximum Motorsports.
Before we delve into the details of this killer suspension setup, let us dispel any doubts. We’re not talking about a tube chassis front clip, back-halfing the car, or anything crazy, just a well-engineered group of easily installed parts that address the Fox-body platform’s shortcomings from front to back. This not only means a completely transformed Mustang when you’re done, but any qualified gearhead can install the parts at home. MM also has some of the best tech support in the business that’s only a phone call or email away.
Suspension Physics: 101
OK, one more bit of information before we really get started here. Jack Hidley explained several important aspects of the Fox-body’s suspension setup: the center of gravity (CG), instant center (IC), and roll center (RC).
The first, CG, is basically just the balance point on any given car. In theory, if you balanced a car on its CG, a fixed point, the wheels could be removed and it would simply balance. The CG works alongside the IC in the sense that if you look at the (imaginary) triangle the stock four-link suspension forms with its two upper and two lower control arms (when viewed from the side), and you made an imaginary line, the lines would converge at the IC. The IC changes with ride height and control arm-mounting locations. Why do you care? Because managing how the IC moves around the CG dictates how quickly and effectively the rear tires are loaded and moving your car forward. In lay terms, it affects traction.
The second part of the equation is the antisquat line (AL), which is the imaginary line on a solid-axle car that extends from the contact patch of the rear tires to where the front axle vertical centerline reaches the height of the CG. Dividing the slope of the antisquat line by the 100 percent squat line determines the amount of antisquat in the rear suspension. When the car has 100 percent antisquat, all of the acceleration forces are instantly transferred to the tires. When the car has 50 percent antisquat, half of the acceleration force is applied to the springs, shocks, and rear suspension, and therefore the car squats before rebounding back and into the tire. Antisquat is basically how quickly the acceleration forces are transferred to the tire. I know, it’s all a bit much, but to truly understand how serious MM takes suspension design, one must understand a snippet of the engineering that’s behind every piece.
The Front First
The Fox-body platform might have been revolutionary back in the late ’70s, but time and technology marches on. What was once groundbreaking eventually becomes antiquated.
It all starts with a tubular K-member that improves suspension geometry, while simultaneously preserving the desirable aspects of the stock suspension at lower ride heights. Typically, lowering your car ruins the geometry, but the MM kit improves it while lowering the ride height for a one-two punch.
“The K-member improves suspension geometry by raising both the front control arm pivots so that suspension geometry is optimized with a lower ride-height,” Hidley added.
There are two front lower control arm pivots 1 inch and 2 inches above the stock location; raising these pivots lowers the roll center and diminishes body roll. The K-member also moves the front centerline of the spindle 3/4 inch forward. There are three different lower control arm options that include 3/4-inch rearward offset, nonoffset, and 3/4-inch forward offset, and when they’re paired with the offset of the K-member it results in three different offset options of stock as well as 3/4-inch and 1 1/2-inch forward offset. With SN95 control arms, the wheels can also be pushed outward. The increased stability of widening a car’s track width is obvious, but moving them forward has an equally beneficial effect.
Hidley explained, “Moving the wheels forward has the same effect as moving the Center of Gravity rearwards, which places more weight on the rear tires for better braking and acceleration. Also, the engine can be mounted in the stock location or back 1 inch to shift even more weight rearward.”
The benefits of having more weight on the rear tires for acceleration are, again, pretty obvious, but did you know that less weight (to a certain extent) on the smaller, narrower front tires also helps under braking as well as in the turns since nose-heavy stock Mustangs easily overwhelm their front tires to the point of locking the brakes or understeering in a corner? The MM K-member helps fix both problems.
The MM K-member also helps improve the Ackermann steering effect. Yep, another engineering buzzword—MM is full of them. The Ackermann effect basically explains that when a car is turning a corner, the inside wheel is not only rotating slower than the outside wheel but also needs to turn at a different angle, because the inside tires are following a smaller arch. The stock Fox-body Mustangs have little to no Ackermann, creating drag as the inside front tire fights the outside and creates what is known as parallel steering, an effect that causes massive understeer. The MM K-member fixes that, too. The K-member also sheds a ton of weight and has OEM-like durability.
“Our K-member and front suspension pieces save a combined 40 pounds over your stock pieces, while also preserving OEM durability standards, so it won’t wear out in 50,000 miles,” said Hidley.
Beyond the computations, acronyms, and big engineering words, what does it mean from the driver’s seat? Less weight, more grip, more responsive turn-in, a ton more clearance for headers and oil pans, and the ability to actually reach the starter, steering shaft, and other bits that were nearly impossible to access with the stock K-member.
01. The cure? A trip to Maximum Motorsports for a complete suspension swap that started with Luka Dugandzic, the head engineer at MM, grinding off all the old, unnecessary ARB hardware welded to the rearend housing.
02. The crappy, stamped steel, stock lower control arms were replaced with these ultra-trick, Extreme Duty Drag Race rear lower control arms that are as strong as they are trick. Note the adjustable lower perch, which allows for quick ride-height adjustments with a 1/2-inch ratchet, and the high-quality mounting pivots that are strong enough to take anything you can throw at them.
03. Paul Ellis inserts the lower control arms in the torque boxes, but not before applying the included polyurethane grease to the bushings on all mating surfaces, even inside where the bushing and the bearing insert meet.
04. Here’s another crucial piece of the MM suspension system, the Panhard assembly. This high-quality unit controls the side-to-side movement of the rearend, keeping it centered. It lowers the roll center and reduces understeer.
05. The innovative Panhard chassis bracket mounts to the rear framerails with four holes and uses a special insert that allows the bracket to securely attach to the framerail without crushing it.
06. Be sure to take your time when mounting the Panhard bracket in place. Don’t forget to use a plumb bob to make sure the bracket is centered before drilling the holes. Changing the length of the Panhard rod helps center the rearend.
07. The last bit of the three-link trifecta out back is the almighty torque arm from Maximum Motorsports. This amazing piece of engineering allows the rear axle to float in a perfectly controlled arch. The torque arm, Panhard, and lower control arm combo is effective at putting the power down and preventing brake dive. The MM unit is top-rate in construction and literally a work of art. Due to our 600 lb-ft of torque, MM speced their Heavy Duty torque arm.
08. The torque arm mounts to the rear pumpkin and also uses U-bolts that mount around the rear axle. The factory hole on the driver’s side of the pumpkin will need to be enlarged to 9/16 inch. The passenger’s side will need a new 9/16-inch hole drilled inboard of the smaller factory hole. Note that this is only required on heavy-duty torque arms.
09. The torque arm mount uses its own crossmember, which connect to the MM subframe connectors. This mount allows the torque arm to move forward and back as well as angularly to prevent suspension bind. Don’t forget to grease the forward bushing before it’s pushed into the mount.
10. Our car already had MM’s full-length subframe connectors, but while Luka was in there welding the torque arm’s crossmember to the subframes, he also increased the size of the welds on the subframe connectors for a better fit.
Bringing Up the Rear
As you already know, the Fox-body Mustang came from the factory with the Quadra-link rear suspension setup, which is most commonly referred to simply as a four-link. There are two types of four-link suspension designs, but the only one we’re concerned with here is the triangulated four-link. Four-links have exactly that: four mounting points on the axle and four on the frame, two upper and two lower control arms (also called trailing arms). The lower control arms control axletube twist, and the upper arms control both side-to-side movement and axletube twist. In theory, the Quadra-link should work well, but it has been dubbed the “Quadra-bind.”
“The Quadra-link is overconstrained,” said Hidley, “which means the arms are moving on different planes. That leads to roll binding and unpredictable behavior, but it also means that the stock suspension relies on bushing deflection to make up for the conflicting geometry. This means that, should you switch to spherical-joint or stiffer bushings, it only exacerbates the problem and in many cases can destroy the mounting points on the body.”
To be fair, a Quadra-link can work effectively for drag racing with the proper reinforcements and supporting pieces, but throw it in some corners, especially ones with some bumps, and it becomes unpredictable at best. As the suspension moves vertically and laterally, it binds. And if driven aggressively enough, the car becomes unpredictable as the suspension binds and suddenly unloads, causing snap-oversteer and other driving dynamics that will cause anyone short of a pro driver to soil his pantaloons.
Our previous four-link worked well at the dragstrip, but throwing it into a curve was laughable at best. Before adding the rear antiroll bar (ARB) it would wallow and protest, and after the ARB the front would still wallow, while the overly stiff rear would lift the inside tire. How do we achieve the best of both worlds? We ditch the upper control arms and add a torque arm and a Panhard bar.
That’s right. The minute the upper control arms leave the party, so does the roll binding. That doesn’t mean you can ditch your stockers and call it a day. Oh no. What it means is that beefier lower control arms from MM replace your flimsy, stamped steel stockers, while a torque arm and a Panhard bar join the team to keep the axletube from rotating, binding, or doing the Rumba under your Fox.
“The torque arm and Panhard setup reduces suspension binding, which makes the car more predictable, improves rear traction under acceleration and deceleration, and improves ride quality,” said Hidley.
The term rear traction is key here because it’s not just on the throttle; it’s also while braking. Torque arms exhibit less brake dive since they transfer the braking forces into the body, actually applying an upward force on the front end that combats the downward force from braking.
Maximum Motorsports chooses a Panhard bar instead of a Watts link to locate the rearend because it is far less complicated, lighter, more cost effective and smaller than a complicated Watts link.
“The stock four-link has as much as 2 inches of lateral movement throughout its travel, while our Panhard has less than 1/8 inch of lateral movement between the entire motion of travel, a scenario nobody would see in reality since it’s nearly impossible to have the suspension move from full droop to fully compressed while cornering,” Hidley explained.
Sure, a Panhard introduces a slight arch in rear suspension travel compared to a Watts link, but the arch is minuscule, and for the aforementioned obvious reasons the Panhard is the part of choice for MM. “It’s much smaller than a Watts link, which makes fitting an exhaust system a lot easier, not to mention it’s lighter and just as effective on the Fox platform,” Hidley added. Again, what does this all mean? Well, it means more traction, stability, and consistency for a Fox-body at the dragstrip and in the corners. It also means you’ll want to spend as much time staring at the underside of your Mustang as the topside.
How Does It Drive?
Simply put, the car is an entirely different animal with the Maximum Motorsports suspension. Gone is the wallowing whale that was only effective in a straight line. The car now turns in like a Boss 302 with minimal body roll. Composure at the limit on the amazingly sticky Mickey Thompson Street Comp tires is stunning. Rear traction is much improved. Brake dive is virtually nonexistent. Seriously, it handles so well that it doesn’t even feel like a Fox-body. Of course, on a bumpy road there’s no hiding that it’s still a live-axle car, but it’s nothing like the stock setup.
It is important to note that the addition of the torque arm slightly increased noise, vibration, and harshness (NVH), as on/off throttle transitions transfer some ring-and-pinion clunks into the cabin. It isn’t obnoxious by any means, but worth noting. Some will also note that the torque arm and Panhard bar setup adds weight, but when installed along with the lighter K-member the increase is only about 35 pounds.
Turn and Burn
To put our money where our mouth was, we headed to the Pleasanton Fairgrounds for a Goodguys Autocross event. As luck would have it, the course was the tightest it had been in years, so our 600-plus smog-legal ponies didn’t mean much. However, the rest of the MM suspension and SVE braking upgrades made a world of difference when riding on lightweight Enkei RPF1 wheels (thanks for letting us borrow those, Jack!) wrapped in Mickey Thompson Street Comp tires.
With MM hot shoe Mike Croutcher behind the wheel, the Smog-Legal Killer finished sixth out of more than 40 cars. To make things better, ours was the only car in the top 10 to drive to the event and the only car in the top 10 not wearing near-R-compound 200-treadware tires. We drove there on our MTs, aired them down, and threw down, pulling 1.06 g’s of lateral grip in the corners!
After the Goodguys Autocross, we drove the Smog-Legal Killer to Sacramento Raceway, changed suspension settings, bolted on our lightweight and sinister-looking SVE Drag wheels wrapped in Mickey Thompson ET Drag tires in a 28x10.5S variant, and proceeded to cut our best 60-foot time of 1.39 seconds just moments before the T5 transmission bit the dust on the 1-2 shift—our best 60-foot on the four-link was 1.47. Hey, it happens. But that didn’t stop us.
The MM setup had a unique look launching out of the hole that was reminiscent of early Mopars in that it raised up and rocked out rather than squatting and unloading like a typical Fox-body. Had the T5 not broken, we are sure it would have gone faster than the previous four-link best of 10.80 at 123 mph.
After many months and even more mods, we again grabbed Drew Wallace of AED and paid a visit to the track. This time we were making more power thanks to the AMS Power Pipe and Pro-M standalone, as well as the Flowmaster and Kooks exhaust, but we were also in a bit of predicament. Although the Tremec Magnum powershifted like a champ, its optional 2.66 First gear was much taller than the T5’s 2.95 First, so it was difficult to nail a great launch. With 5,500 rpm on the dial, the car would bog, but with 5,600 rpm it would spin; it was like balancing on a wire and the car was experiencing some hoping under acceleration. Nonetheless, the car ran a 10.79 at 128 mph on a 1.57 60-foot.
11. For those using the HD torque arm, you’ll have to modify your mid-pipe to clear the torque arm crossmember—however, standard-duty torque arms will clear all factory-style exhaust system. Don’t worry; it’s nothing a local exhaust shop can’t handle.
12. Next up is the rear sway bar. The MM unit is unique in that the lower mounts attach to the axle and the upper mounts are welded to the framerails for a supremely stiff setup. Our unit was MM’s 1-inch hollow sway bar with 1/8-inch thickness.
13. Here’s a close-up shot of the upper rear sway bar mount welded in place. Note the multiple mounting points that allow for varying degrees of stiffness.
14. With the rearend ready to go, we installed the MM-spec variable rate, 290- to 350-lb/in springs These were selected as the perfect compromise between dragstrip and road course performance.
15. The rear shocks mount to the axletube with a special MM mount. We chose Koni single adjustable shocks for the job.
16. According to Internet lore, exhaust tips can’t be used with a torque arm and a Panhard bar. We’re here to tell you that the Latemodel Restoration stainless steel 2 1/2-inch units easily fit and looked great poking below the bumper.
17. The Maximum Motorspors K-member is another work of art. It is much lighter than the stock unit, is just as durable, and improves suspension geometry for more grip and better weight distribution.
18. Luka and Jack of MM can be seen installing the K-member. Note that the engine is being supported from above.
19. Be sure to follow the instructions given by MM when centering the K-member. Tape measures and plumb bobs are your friends! Once everything is centered, a small hole can be drilled through the K-member mounting plate and the body to aide in alignment should you ever need to remove the K-member.
20. Between the 3/4-inch forward offset that the K-member gives you and the three different lower control arms that MM offers, you can move the wheel as much as 1 1/2 inches forward or leave it in the stock location. Trust us, MM is the real deal when it comes to making your Mustang handle, stop, and launch.
Still unhappy with the results since we couldn’t get the launch down, we had Rivercity Differentials add Ford Racing 4.10 gears in place of the 3.73s. The result? We could come out at 4,500 rpm and blow the tires off. With more gear, we experimented with launch techniques until we discovered that quickly feeding out the clutch rather than dumping it worked the best to the tune of a 10.79 at 130 mph on a 1.56 60-foot. Our ET was still the same, but the steeper gears gave us a few mph.
As with the previous outing, shock settings did little to curb the hopping we could visibly see, feel and verify with our Racelogic VBOX Sport. As the temperatures fell and the track went away, we packed up and headed home just days before deadline. The day after, our number crunching verified our suspicions at the track, that there was too much rear antisquat and it was hurting traction. (Note: as with any adjustable suspension, tuning is necessary to achieve maximum performance.) We attempted to lower the rear ride-height to minimize the antisquat, but our combination of Extreme Duty Drag Race rear lower control arms and springs were already at their lowest positions.
We’d be lying if we said we weren’t a little bummed that our user error held us back, but that’s racing. That’s what keeps it fun, because it’s challenging. But the proof is there: We cut a 1.39 60-foot and knocked down 1.06 g’s on the skidpad with one suspension, and the only changes between both showings was ride height and shock settings (and of course wheel/tire changes, but that’s it). We’re not making excuses, but had we been able to reduce the antisquat, we’re sure deep 10s were within reach. But such is life. We built a car that was the best of handling and launching, which meant there were compromises on either end in order to draw a line down the middle.
So as we wrap up the Smog-Legal Killer we can’t help but feel a little nostalgic. Wait a minute. Who are we kidding? We’ve still got some tricks up our sleeve, because as they say, a project car is never finished.
21. Don’t forget the MM K-member brace. This puppy helps with turn-in and is adjustable to clear deep oil pans like our 8-quart Milodon pan.
22. The MM adjustable steering rack bushings are not only solidly mounted for the utmost performance and feedback, but they’re also adjustable to help with bumpsteer and Ackermann. Seriously, MM thinks of everything!
23. Ah, the world-famous MM caster/camber plates also joined the party. These units are legendary in the Mustang world because they work unbelievably well, install with ease, and are beyond durable.
24. Here’s a shot of the MM 225-lb/in front springs, the Koni single adjustable front shocks, and the MM coilover sleeves. This is the stuff corner-carving dreams are made of!
25. The collapsible MM steering shaft is another industry legend, as it cuts down on steering slop by killing the factory rag-joint and replacing it with a hard U-joint. Its burly construction is offset by its collapsible feature should you get in a frontal impact. We had to dent one of our primary header tubes to clear the shaft, which wasn’t a big deal.
26. Here’s a shot of the adjustable front sway bar brackets and the OEM GT sway bar that we also added to the mix. Prior to all the suspension the coupe lacked a front sway bar.
27. Jack Hidley of MM shared his secret fender mods that allowed us to run 275/40-17 tires on all corners. These spreader bars help push the lower fender out, while the trimming of the lower fender, the rolling of the outer fender, and the extending of the inner fender all created just enough space to tuck wide front tires in the small Fox-body wells.
28. The Maximum Motorsports suspension is nearly as pretty as it is functional. Look at all that high-performance beauty. It’s a shame we can’t see it from the driver’s seat, but we can certainly feel it!
29. Say goodbye to the body roll and hello to BOSS 302-like handling. The ol’ coupe pulled 1.06 g’s of lateral grip with the MM suspension and the Mickey Thompson Street Comp tires . . . and all four tires are now on the ground.
30. The SVE Drag wheels shed a ton of weight, looked killer in their Dark Stainless finish, and didn’t break the bank. The 17-inch front skinnies cleared our SVE Cobra
The Steering Rack Epidemic and Terminator Cobra Rack Rebuild
It’s buyer beware when purchasing a remanufactured steering rack for your Mustang these days. How do we know? Because we were burned three times!
Before sharing our story, let us remind you that although all SN95 through New Edge steering racks look identical from the outside, it’s the internals that make a world of difference. A V-6 rack might look like a Terminator Cobra rack on the outside, but driving dynamics couldn’t be more dissimilar. The Termi rack is perfectly weighted with quick response and a better ratio compared to the V-6, which is mushy and numb.
We paid a visit to a local parts store to buy what we thought was a remanufactured Terminator rack that developed a leak on the first drive. We swapped the rack for another, and although it had an identical part number, it felt completely different with a ton more boost. Perplexed, we called the folks at Maximum Motorsports and they let us in on a secret. Many rack rebuilders don’t put the same internal parts back inside the rack as it’s being rebuilt. Rather, all Mustang rack internals are thrown in a box and are used on a whim when Mustang racks are rebuilt. In other words, the Terminator rack you think you’re buying could actually be a bastardized unit with a mixture of GT, Cobra, and V-6 parts. Not cool.
So we bought a genuine Terminator rack off eBay that proceeded to leak on the first drive as well. Strike three! Thankfully Turn One came to the rescue. Turn One is the place to go for high-performance steering racks and world-class rebuilds. The company is familiar with the remanufactured mismatched rack epidemic silently plaguing the Mustang scene. The guys there took it down to a bare core and painstakingly rebuilt it to better-than-stock specs. They even dyno-test their racks to ensure that they function as expected. Seriously, if you have a genuine Cobra, Terminator, Mach 1, or the ultra-rare 2000 Cobra R rack, do not—let me repeat, do not—turn it into a local parts store because you’ll likely never get another. Instead, contact a company like Turn One and have them rebuild your exact rack—it’s money well spent.