5.0 Mustang & Super FordsHow To Chassis Suspension
Fox Mustang Suspension Upgrades - Old Fox, New Trot
Fox Mustang Suspensions Need Help These Days-Here's How We Upgraded Ours
Should you be opting for more aggressive lowering than we are in this story, you might consider upgrading to adjustable tie-rod ends, commonly known as bumpsteer kits. Bumpsteer is a symptom of toe changes from the suspension moving up and down, which can actually cause the car to change direction. Maximum Motorsports offers two variations of the adjustable tie rods, one with a tapered stud for stock K-members and one with a bolt-through spindle for its tubular unit. Obviously the latter offers a greater range of adjustment than the former. It also costs a bit more at $149, versus $139 for the tapered-stud version.
While never known as the tightest ships in the fleet, Fox-chassis Mustangs are at that age where creaks and groans accompany nearly any motion. Good as you are to your 5.0, no doubt you've noticed it wandering on the freeway, wallowing through culverts, and generally feeling loose. It's time to lavish some love on the chassis.
From the most fastidiously maintained personal favorite to run-hard beaters, old 5.0s fall prey to time and mileage. With 100,000 miles being low mileage for today's Fox Mustangs, is it any wonder the typical chassis wear points are highly suspect? Tires, struts, and shocks are all no-brainer maintenance items in this age group. But for many owners, changing bushings in the control arms, steering rack, sway bars, and other areas is a first-time concern, as is the condition of the rag joint in the steering, the inner and outer tie rods, the pinion snubber, and the spring isolators. In short, if it's rubber or plastic and it's been working for a decade or more under your Mustang, it should at least be looked at.
To get a better idea, slide onto your imaginary creeper with us and take a quick tour from grille to taillights under a 5.0. Item one is the front sway bar. A simple steel bar, nothing bothers this thing short of hitting a tree, but the bushings it pivots in soften, crack, and loosen up, and the end-links almost always bend. The bending comes from the sharp angle the end links are contoured to during maximum sway bar deflection. Curiously, the light blue end-link bushings are probably the most durable bushings in a 5.0. While likely slightly deformed, they are probably OK.
Next back is the steering rack. Its only common wear items are the inner tie-rod ends. These are a typical cause of freeway wander and "loose" steering. The rubber boots on the rack are occasionally rotten or punctured as well.
On the outer end of the rack are the outer tie-rod ends. These do wear, but not as rapidly as the inner variety. Also, they are easier and less expensive to replace, so they may have already been changed.
Between the steering rack and the upper steering column is an intermediate steering shaft, commonly called the rag joint or steering isolator. It is a common wear point and source of wandering steering on 5.0s. Cracking and deformation are the typical failure modes. Any visible play while a buddy works the steering wheel back and forth in small, sharp motions is also cause for replacement.
On the front lower control arms, consider the control arm itself-they do crack. In addition, the ball joint at the spindle end will wear and the large inner bushings where the arm attaches to the K-member crack and mush with age. A steady diet of extremely hard driving will even squish the control arm bushings out of the A-arms, a condition the mechanics at the Bondurant driving school reported took about one month to occur on the school cars. Those cars are driven like rented mules all day, every day, and we mention the phenomena in case you're working on an old race car or your 5.0 has taken a couple of kids through high school.
The weakest point of the Fox chassis is the midsection, in a line running athwart the car just forward of the rear of the door opening. Look for cracks in the floorpan, especially around the holes where the seats bolt to the floorpan. The solution, as well as the preventative medicine, is a beefy set of weld-in subframe connectors.
Likewise, with the rear suspension, eyeball the chassis where the upper and lower control arms attach. In cars driven hard -drag racing starts are the culprit-these attachment points can be cracked or torn away from the chassis proper. Reinforcement with patch panels and a welder are the answer.
More commonly, the control-arm bushings may have succumbed to ozone cracking and hard driving. This is most important with the lower control arms; the upper arms are built with soft bushings to provide the definitely needed compliance in the rear suspension to avoid binding between the upper and lower control arms. When eyeballing the lower control-arm bushings, keep in mind the forward end of the lower arm uses an elongated bushing, so don't be overly alarmed if you can see some clearance between one side of the bolt and rubber bushing.
The spring isolators between the coil spring and the lower control arms are almost certainly turned to powder. This is almost always the cause of the "settling" of the rear ride height normally attributed to the rear springs. While the springs can settle with age, it is not nearly as often as is commonly thought. It's usually just dusted spring isolators.
Of course, the hard-working shocks are almost always ready for replacement. Another given is the rear sway bar is just fine. It bolts directly to the lower control arms and uses no rubber bushings, so it's good for life. Also, the kicker shocks are probably OK as is. They're there to dampen rear-axle reaction motions and thus avoid axle hop during hard starts. If axle tramp is not an issue with you, there's little need to service these units.
What To Do About It
The fun begins when formulating a plan of chassis restoration. A couple practical issues soon become apparent. For starters, a few of the common wear items are obsolete from Ford, so you'll have to go aftermarket for some parts. You'll want to go aftermarket on other parts because a handful of the stock Ford parts are best replaced with stronger aftermarket items. And, most importantly to the enthusiast, simply renewing factory levels of performance is often not as exciting as stepping up the game somewhat. Therefore, fixing up a Fox chassis is just the excuse you were looking for to install a set of lowering springs or more sports-oriented handling. Other times-and you old-timers reading this magazine know who you are-providing a showroom-new ride to your Fox is all you want. Let the kids pound their kidneys.
To get to the bottom line, restoring a Fox chassis typically means upgrading a Fox chassis, and for that, a parts package often makes sense. There are several choices readily available, depending on your car's condition, desired result, and budget. Should you want them, total performance suspension replacement and chassis mods are available for north of $5,000-but that's not what we're addressing in this article.
This time around we're aimed at daily driver Mustangs-our own 150,000-mile '91 5.0 LX hatchback proved a good example. Never raced, and used as a daily driver by two older enthusiasts its entire life, it was still a candidate for suspension work. We admit it was generally "loose," but what got us to finally look underneath was a lazy wander on the freeway. That turned out to be a worn inner tie rod. Simply replacing it would have returned the old hatch to daily service but still not quite showroom-new manners, and certainly nothing as precise as would be desirable.
For a casual driver such as our car, a favorite package is the Eibach Pro System Plus-offered direct from Eibach and numerous dealers, including Maximum Motorsports, for example. This is an affordable ($1,247.35) spring, shock, and sway-bar kit offering a 1.5-inch lowering with a ride quality a notch more sporting than stock. Fitting it would give us fresh shocks all around, as well as the new ride height from the new springs and the matching roll stiffness from the slightly larger sway bars.
Other parts were sourced mainly from our local Ford dealer and Maximum Motorsports. The photos and captions have details on these, but the idea was to replace the necessary items and support the Pro System Plus kit with durable isolators and other small parts.
While not shown here, the Ford Racing Performance Parts catalog offers front and rear upper control arms, complete with bushings and ball joints. These are excellent options should you have worn control-arm bushings or cracked control arms. The price is reasonable ($189.95, front; $102.90, rear) installa-tion is as simple as it can get because the bushings and ball joints are already mounted in the control arms, and upgraded ball joints and bushings are fitted where appropriate. FRPP also offers heavily upgraded rear lower arms as well.
On our '91 hatch, we had Eibach install its Pro System Plus kit, a new power-steering rack, Prothane urethane steering rack bushings (supplied by Maximum Motorsports), and Maximum Motorsports urethane spring isolators front and rear. We reused the existing outer tie-rod ends along with the original rag joint in the steering. (We'd go with a solid shaft or new rag joint along with FRPP front control arms if we were to redo this job, to ensure maximum longevity from this hopefully do-it-once maintenance and upgrade).
The steering rack was an interesting twist on dealing with inner tie-rod ends. A rebuilt Ford unit sold by partsquest.com, the rebuilt rack retails for $209.87, and is possibly easier to change than the inner tie-rod ends (they're heavily torqued and require large wrenches). If there is a downside of changing the rack, it's the sometimes oily mess from opening and flushing the power-steering lines. But depending on local labor rates, this option may beat having the tire and alignment shop install only inner tie-rod ends.
When finished, our Mustang stood a perfectly beautiful 1 inch lower than stock, rather than the usual 1.5-inch drop advertised for the Pro System kits. This is because the large, urethane Maximum Motorsports spring isolators are thicker than stock and so provide a small ride-height lift. Stock isolators and the Eibach gear would drop the ride height 1.5 inches. Lowering fiends have been known to leave out the isolators-not recommended due to noise and deteriorating handling-and get a 1.75-2.00-inch lowering. That's too much lowering for optimum handling, but some folks will do anything for looks.
The ride is slightly stiffer than stock, daily-driver friendly, yet firmly controlled. The steering is a notch tighter than stock, and generally the car is more eager and willing to hustle through turns. So far we've noticed only minor increases in front-end scraping out of the steepest driveways, or dragging our lower-than-stock exhaust over speed bumps and such.
It's been the fun way to take care of old chassis issues!
Rubber, Urethane, Or Steel?
Just as it's normal to be tempted by too large a cam when building an engine, it's easy to get carried away with urethane or steel rod ends when building a suspension.
There are good reasons why all street cars come with rubber bushings in the control arms. Rubber bushings don't actually rotate-they simply deform or twist the rubber when the control arm moves. While this sounds sloppy to the enthusiast, rubber bushings actually allow a smooth, predictable suspension action with easily acceptable amounts of friction and additional spring rate as the suspension reaches its stops. And compared to the highly desirable buzz and shock dampening they provide, rubber bushings don't allow all that much unwanted slop. Also important, rubber bushings are highly tolerant of slightly misaligned bushing bores in the control arms and chassis. The OEMs count on this compliance, so they don't go out of their way to align the various suspension bores.
Urethane bushings are much less compliant than rubber, so their attraction is more precision in the suspension action. For control arms this is a wonderful thing, provided you go to the considerable trouble of blueprinting the bushings during installation. The control arms must fall through their arc with no more pressure than their own weight, and that means shaving a bit here, rotating there, and so on. Just slamming in a set of urethane control-arm bushings is not going to get you what you want. Durable, semi-rigid urethane is a slam-dunk for the steering rack, the sway-bar bushings and links, and the spring isolators, however.
Steel bushings, i.e., rod end bearings, are pure race-car fare. They offer no compliance and wear rapidly. So, while they look sexy, they're definitely high maintenance. Leave them for the track stars.
Traditionally, coilover spring/shock units have been pricey and worthwhile only for race cars. However, Eibach has noted many customers have gone to coilovers on street cars just to have a convenient way of adjusting their ride height. With that in mind, Eibach has developed a Mustang coilover system designed to be quiet and durable in street use, yield the same ride and handling of its Pro System kits, offer as much affordability as possible ($1,500 retail), and provide the all-important ride-height adjustment, but not the high-cost niceties or punishing ride of a race-bred coilover system.
The new units are a direct replacement for the stock spring and shocks and do not require reinforcement of the shock mounts. The front units accept either stock or Eibach's caster/camber plates, and use a small, soft coil spring atop the main coil spring. This tensioner spring is normally fully compressed and has no traditional spring function. It's there strictly to provide light compression pressure on the main spring when the strut is fully extended. This avoids bothersome popping and rattling when traversing culverts or when the car is raised on a hoist.
Furthermore, because of the extra spring rate gained by moving the spring outboard relative to the lower control arm, the coilovers provide enough spring rate that the stock front sway bar is sufficient.
At the rear the spring and shock remain mounted separately. A mounting wedge provides the necessary spring angle, while a large aluminum collar/seat assembly provides adjustability.