Tom Wilson
May 2, 2014

Horse Sense:
These days Maximum Mustang caster/camber plates carry a lifetime warranty—something of a rarity for aftermarket parts, which speaks volumes about their durability.


So, you put lowering springs in your Mustang and now the alignment shop has called saying they can't get the camber where it needs to be and you need a set of camber plates. What are those?

Caster/camber plates are a popular, but often-ignored Mustang bolt-on. Obviously, they allow adjustment of front-end alignment, but the details of just what caster/camber plates adjust, how they are built and installed often seem murky. To get the straight scoop we traveled to Maximum Motorsports, who are, if not the sole inventor of this alignment device, are definitely the major developer and seller of the caster/camber plate as we've known it for the last 20 years.

Since the first Fox Mustangs roamed the planet, they have had a MacPherson strut front suspension. It's an economical layout employing an over-sized shock absorber—the strut—in a dual role as both suspension damper and suspension locating device. The strut is attached to the lower control arm (via the steering spindle) at the bottom, and the chassis at its top. In fact, the round bump in the engine compartment where the strut bolts to the body is called the strut tower, and it's at the top of the strut tower where the caster/camber plate reigns.

Because the strut defines the top location of the suspension geometry it is a major player in setting the suspension's alignment. Specifically, moving the top of the strut toward or away from the center of the car adjusts camber while moving the top of the strut forward and backward along the length of the car determines caster.

One characteristic of the Fox front suspension chassis tuners soon came to understand was it did not have enough caster. Because camber and caster are interconnected, maximizing camber cost desirable negative camber when the front tires were steered away from center just when negative camber is needed—while cornering.

When a strut Mustang's ride height is lowered—think lowering springs—negative camber is increased to harmful levels on street cars. Thus, the typical Fox enthusiast who was driving hard in the corners needed some help increasing caster, and if his car was lowered, he needed help in regaining the stock Ford camber setting as well.

In the mid-'80s, Global West was the first to offer a bolt-on solution with their caster plates. These allowed adjusting in increased in caster, but they were not easily adjustable for camber. Instead, Global West offered two versions of their plate; the Street version yielded stock Ford camber, the Race version delivered increased negative camber for track cars, but in either case the camber was not readily adjustable.

Caster/camber plates provide the same basic alignment function on all Mustangs, but different Mustang chassis have different alignment needs. An S197 such as this has all the caster it could ever use on a race track while sitting on the showroom floor, for example. But it could definitely use more camber if taken to the track. A lowered Fox needs both increased caster and reduced negative camber if street driven.
This is the kit that started it all (PN MMCC7989) for ’79-’89 Mustangs. The key concept is that the flat, vaguely triangular-shaped plates set camber, while the bearing retainer with the Teflon-sealed spherical bearing and two studs set caster. Maximum notes it started buying bearings 5,000 at a time when the supplier offered the exact size desired, eliminating the need for a sleeve used previously. The black cones are bumpstops to help with lowered cars.
When Ford changed the Fox caster specification in 1990, it also changed some strut-top hardware, including the strut tower itself. This required subtle length and slot changes to the Maximum main plate, as shown by the ’79-’89 plates at top and ’90-’93 plates in the bottom row. Passenger-side plates are to the left. It’s possible to file the later strut towers to allow the earlier caster/camber plates, but they’ll sit askew to the tower and don’t give the same range or ease of adjustment. Mixing up early and late Fox caster/camber plates is a typical swap-meet problem, so beware.
Matching the early and late Fox main plates are these ’79-’89 (left) and ’90-’93 (right) bottom plates. The physical differences are too subtle to see, just a 1⁄8-inch movement in the studs, but it’s enough that the plates are not interchangeable. To keep things sorted, Maximum gives the ’90-’93 plates an identifying notch, seen on the right-hand edge here.
Conceptually identical to Fox plates, Maximum’s MMCC9994 plates for ’94-’04 Mustangs differ mainly in they use a four-bolt mount. This means drilling one hole in the strut tower, but the payoff is a vastly stronger plate that will not bend under anything less than crash conditions.

In the later '80s, Central Coast Mustang released a similar plate that gave a fixed caster—greater than stock—and fixed camber, again in two positions for either stock or lowered ride heights. Then, in 1993, Maximum Motorsport introduced the fully adjustable caster/camber plate. This is the now-familiar two-plate device that allowed adjusting caster and camber independently of each other, and gave a larger range of adjustment than Ford provided. The Maximum caster/camber plate was an instant success and has been copied many times, but never really improved upon.

Unfortunately for Maximum Motorsport, its original two-plate design was not patented—the company didn't have the money at the time for the application fee—so the concept was an open source from the beginning. Later Maximum designs are patented and offered by nearly everyone.

Of course, as Ford developed the Mustang, changes to the camber plates were necessary. Up to 1989, the Fox shock tower and camber plate was mainly unchanged, but in 1990, Ford dialed in a bit more caster (but not enough), relocating the strut-mount holes in the shock tower in the process. Many enthusiasts and some shops missed this unannounced change. Maximum, which opened for business in 1992, discovered the difference immediately while researching its original plate design, and has always offered early and late Fox caster/camber plates.

When the SN-95 Mustang debuted in 1994, it required yet another variation of the caster/camber plate from Maximum. It was similar in concept to the Fox plate, but not interchangeable.

A big change came in 1999, when Maximum added a fourth mounting bolt to its caster/camber plate. The three-bolt plates using Ford's original bolt pattern would bend under extreme pounding with coilovers, or when accidentally taken off-track at speed during spins, or as crash avoidance. The issue, found only on SN-95s, was that Ford's three-bolt pattern left the upper strut tower cantilevered off to one side with track suspension settings, overloading the plates. The solution was boxing the upper strut with a fourth plate stud. This required drilling a fourth hole in the strut tower for the new stud to pass through, but doing so increased strength greatly. The new SN-95 four-bolt caster/camber plates made the previous three-bolt units obsolete, so Maximum discontinued the earlier design for SN-95s. Fox Mustangs have never needed or had a four-bolt plate from Maximum.

When the S197 Mustang debuted in 2005, its all-new, completely non-adjustable, four-bolt upper strut mount required an entirely new plate from Maximum. Maximum's design used the same two-plate, four-bolt concept of its earlier caster-camber plates, but mounted inside the strut tower. Thus, the current Mustang's caster/camber plate from Maximum is not visible from underhood, but it does give the necessary adjustment to account for chassis aging, crash damage, and, of course, lowered ride heights from lowering springs, along with performance alignment specifications.

In 2011, Ford significantly modified the grip and thread lengths of the upper mounting threads on the struts used in the garden variety V-6 and Mustang GTs, while leaving the GT500 and FRPP struts alone. This meant Maximum had to develop two caster/camber plates for '11-and-later Mustangs, and customers had to know which struts they have on their cars. In the meantime, Maximum is working on a third S197 caster-camber plate that will work with all variations of the S197 struts. Look for the new plate later this year.

There are more details in the photos, along with a review of caster/camber plate installation, on both Fox/SN-95 and S197 chassis. Just remember caster/camber plates have a specific job, and different Mustang chassis have different need of their services.

Showy types have prompted Maximum to offer chrome plated caster/camber kits for pre-S197 cars. Just the main plates get the shiny treatment, which looks good with Maximum’s normal cad-plated hardware. To order a chrome kit put a –C after the normal Maximum part number.
Putting a stock Ford SN-95 upper strut mount next to Maximum’s lower plate for the same application best shows why Maximum’s four-bolt solution was necessary on SN-95s. On the black mount, the three studs form a triangle, but the center hole, which represents where the strut top passes through, can be just outside one leg of the triangle. This overloads two of the studs and bends plates under extreme loads. The four-bolt solution easily boxes the strut inside a rectangle, more evenly spreading the loads. On Foxes the stock three-bolt “triangle” always captures the upper strut, so a four-bolt Fox plate is not necessary.
Maximum’s S197 kit won’t be confused with the SN-95 or Fox offerings as the hardware is completely different. All but the kidney-shaped support plates at bottom end up hidden inside the strut tower with these plates.
Ford uses a ball-bearing upper spring perch on S197s. Most owners know these as the source of a popping or graunchy noise when they often fail from dirt intrusion. Maximum replaces the ball bearing with a pair of sliding plastic discs in their upper spring perches shown here. They have proven more durable, and silent.
In 2011, Ford ambushed everyone by shortening the upper strut shaft and altering the non-threaded grip length on Mustang GT and V-6 struts, while leaving the Shelby GT500 and catalog-only FRPP struts at the old spec. This requires different caster/camber plates, as shown by the early all-Mustang S197 strut at left and the ’11-and-later GT/V-6 strut at right. Maximum is working on a universal kit.
There are a surprising number of Ford applications with minor strut or tower differences affecting caster/camber plate installation, and Maximum has them all covered. This is the kit for ’03-‘04 Cobras (PN MMCC0304), which came from Ford with Bilstein struts. Because these Bilsteins have internal bumpstops, Maximum deletes its black cone-shaped bumpstops, as found in the V-6/GT kit, and adds the necessary blue dust bellows at right. This is also a handy kit for those retro-fitting Bilsteins to ’99-’04 Mustang GTs.


Caster & Camber

Don't feel bad if alignment specs aren't your strong suit; most performance fans are weak on suspension tuning.

Camber is perhaps the easier concept. It is the lean the tire takes when seen from the front or rear of the vehicle. If the top of the tire leans toward the center of the car that is negative camber; if the top leans outward compared to the bottom of the tire that is positive camber.

Some negative camber is desirable because the combination of tire construction and suspension movement means about one degree of negative camber translates into nearly zero or neutral camber at the outside front tire when cornering. This presents the tire tread flat to the pavement, maximizing grip and minimizing wear.

How much negative camber is wanted depends on how and where the vehicle is driven. On the street little negative camber is needed because most of the time the car drives straight ahead or is cornered gently. Maybe one degree of negative camber is best. Add in more and the tire wears unevenly (and rapidly), and the steering can be a little darty because a tilted tire wants to roll in a circle, not a straight line. That will tug on the steering as the suspension extends and compresses over bumps, even as the vehicle moves in a straight line.

On the other hand, at the road race track it is typical to run 2.5 degrees of negative camber. The darty steering speeds steering response and the car spends much time cornering hard; if the car is a little darty on the straights the driver can take care of that. It's more important to present the tire flat to the pavement while cornering, hence the large amount of negative camber.

An aggressive track driver benefits from increased negative camber because he compresses the outside front tire and suspension more. A neophyte or casual track driver doesn't work the suspension or tire as hard and doesn't want or need as much negative camber. Workable track-use camber settings range from 1 to 3.5 degrees; 2.5 degrees is where most track/experienced driver combinations end up.

An extreme example of unusual alignment settings is oval track racing. This is specialized stuff, with the chassis biased to corner to the left rather than run straight (the cars spend more time turning than going straight on an oval). This leads to all sorts of asymmetrical, odd-looking alignment settings, including tons of negative camber (3.5 degrees negative is normal on the right front). You can see this on television during NASCAR races. Should a car get bumped so the sheetmetal is bent back to reveal the front tires their alignment looks like a train wreck, but in reality it's normal for them.

Caster is a different kettle of fish. It is the imaginary line running from the upper strut mount (the caster/camber plate) through the lower ball joint. Visualize this by looking from the side of the car. With the MacPherson strut suspension on Fox and later Mustangs this is approximately the path straight through the strut itself. The top of the strut is always behind the lower ball joint (the strut is laid back when viewed from the side of the car), which is called positive caster.

Positive caster is important because it puts the point around which the front tires swing (steer) ahead of the tire's contact patch. That means the drag and friction of the tire's contact patch (where the rubber meets the road) tries to pull the tire behind the point where the steering swings. This promotes stability and self-centering of the front tires. It's the same geometry of a correctly functioning “caster” at the front of a shopping cart.

If you doubt the need for positive caster, try driving a car that's had the rear jacked up so high the top of the strut is ahead of the lower ball joint… it's like trying to drive an axe that's been thrown handle-first. The head of the axe constantly tries to rotate around to the front, and a car setup with negative or even minimal positive caster redefines “darty.”

Caster plays a big role when the steering wheel is turned off center. Positive caster then tends to pull more negative camber on the outside front tire (the left tire when steering right, for example), helping cornering. The combination of some negative camber and positive caster gives increasingly more negative camber on the outside front tire when cornering. That gives stability, low drag and low tire wear while going straight, and more cornering power when turning. Life is good.

Extreme examples of positive caster are found on dragsters. The tires lean way over when steered, such as when turning 90 degrees from the staging lane to the burnout box. Again, you can see this on TV sometimes with rails fitted with tall, skinny front tires. Another place caster is visible is on many German cars, especially Mercedes. Some run as much as 12 degrees of positive caster—must be the need for stability on the autobahn—which is easily spotted as tire lean in parking lots when the steering is turned hard to one side.

Fox Mustangs came with sparse amounts of positive caster and can use all you can give them; SN-95s and S197s have all they need from the factory—about 4 degrees—so you don't want to automatically slam the top of the strut all the way rearward on the later Mustangs as you do with a Fox. And that brings up an important point: when talking suspension with other Mustangers, make sure you're comparing Fox-to-Fox or S197-to-S197 and not something like Fox-to-SN-95 or S197-to-Fox. These cars each need different alignment settings.

Something else to keep in mind is caster is something of a subjective setting while camber is more of an absolute. For street, road racing and slaloming, camber should be identical side-to-side across your Mustang. But caster can vary a little and still work or feel fine. In fact, caster is usually varied a half degree or so on purpose to compensate for road crown on street cars.


Fox/SN-95 Install

Fundamentals to these installs, there are only three stock bolt holes in the strut tower, and the coil spring is not concentric with the strut. This means the caster/camber plate lives on top of the strut tower, the strut can be removed without having to pop the spring out of place, and a single hole must be drilled atop each SN-95 strut tower, but not in the Fox tower.

1. Fox/SN-95 Mustangs don’t require removal of the spring from the lower control arm to install a caster/camber plate, but it is necessary to fully control spring/lower control arm movement while removing the strut. A floor jack under the control arm and enough room to swing it are a prime requirement.

2. Start by removing all equipment above the strut tower, including the stock adjusting plate as shown. An air gun for the large nut atop the strut really speeds this job, but isn’t a must-have.

3. Once the strut is removed from the car, Maximum’s instructions detail how to use the stock Ford top plate as a drilling template on SN-95s. The plate is rotated 180 degrees from stock to locate and mark the spot for the necessary fourth bolt hole. This is unnecessary on Foxes.

4. Maximum is using a good-sized portable drill here, but almost any drill will do. Start with a 1⁄8-inch pilot hole, then finish with a 13⁄32-inch bit. The steel here is a bit thick, but not particularly hard, so this is an easy step assuming sharp bits.

5. Luka at Maximum Motorsport gets ready to slip the silver Maximum lower plate under the shock tower, then place the black Maximum upper plate onto the lower’s studs. One person can do this, but as there is some hardware in between the two plates it’s easier with two.

6. While holding the lower plate in position with his left hand, Luka slips the 1⁄4-inch-thick washers over the studs. If you’re by yourself make sure you have all the hardware and plates within reach before you start.

7. Here the upper plate has been slipped over the lower plate studs and washers, and the upper plate mounting hardware is being applied.

8. With the upper plate loosely attached, the bearing retainer goes on next. Maximum uses Teflon sealed upper bearings. Do not lube these in any way as oil or grease only holds grit, which wears out the bearing.

9. Our subject SN-95 was already wearing aftermarket Bilstein shocks (Maximum’s go-to shock), so the stock Ford dust boot was not reused and we can’t show the bumpstop installation (it’s no-brainer easy). Depending on the shock and the car’s ride height (stock or lowered), the instructions detail which series of spacers is fitted to the top of the shock’s strut.

10. With the caster/camber plate fully, but loosely, assembled, the strut is reset into position and gunned to the bearing retainer. Once all the lower strut connections—two large bolts, brake-like bracket—are reattached in the wheelwell, the caster/camber plate can be eyeballed for either Fox or SN-95 alignment as appropriate, then the car should go to a pro shop for alignment.

11. The finished installation positions the strut top slightly higher than stock (but less than it looks because the stock upper bearing is so bulky). Still, it is crucial to check hood clearance with putty to avoid denting the hood! Check clearance before closing the hood at home and again after pro alignment (clearance can change). Swapping spacers from atop to below the bearing retainer plate will gain strut-to-hood clearance. With the plate installed, it’s time for an alignment.


S197 Install

Later Mustangs have four upper strut bolts, package the spring concentrically with the strut and put the caster/camber plate under the strut tower. Thus, the nitty gritty of an S197 caster/camber plate install occurs on the workbench as you build the plate atop the spring/strut assembly. You must disassemble the spring, requiring a specialized spring compressor, or nerves of steel, a healthy respect for the power contained in the partially compressed spring, a signed note to all the lawyers in the world saying your mom said you could do it this way and the will to gun off the big nut atop the strut and let the strut shoot across the garage floor and into the box of Christmas decorations under the bench. If you don't keep your smokes rolled up in the left sleeve of your T, better you take the strut to a local tire/front end shop and let them handle the spring on/off part.

As with all caster/camber plate installs, this one is typically in conjunction with lowering springs. Typically this makes it possible to hand-compress the spring while reassembling the strut assembly because the lowering springs are shorter than stock. A big friend standing by is a major aid for this step.

1. Sometimes tall enough to work with the floorjack under the car means too tall to easily reach the top strut bolts. In that case, this is how the pros do it. On S197s the only time spent on the four upper strut nuts is during strut removal and install.

2. On all Mustangs, it’s necessary to remove the two large bolts holding the lower strut to the spindle. These will come out by hand, but an air gun is a big help. It’s also necessary to unclip the brake line bracket (don’t open the brake line hydraulics), and support the brake/spindle assembly with a zip-tie or wire so it doesn’t hang by the brake hose. Ford has upgraded these bolts on S197s to fine-threaded versions, which Maximum can supply.

3. This is the big moment in S197 caster/camber plate installation: removing the big nut from the top of the strut assembly, which releases the energy in the coil spring. This floor shot method is not the school solution, but pros in a hurry accept the strut shooting five feet when the large nut comes free. You should carry your struts to the local front end shop and their spring compressor.

4. Maximum’s S197 caster/camber plate assembles atop the strut, making installation mainly a bench job. Here the upper spring mount is being removed so its rubber isolator can be pried off and re-used.

5. Maximum supplies a series of tapered and straight spacers for use around the spherical bearing. The two tapered bushings fit into the spherical bearing while the straight bushings go on the strut shaft. Like everything else, Maximum’s instructions provide clear step-by-step details.

6. S197 camber/caster plates are loosely assembled with their spacers and stud plates, then held together with rubber bands. It’s an elegantly simple way of holding the plates together before slipping them over the strut shaft.

7. The disc at left is the upper spring perch assembly and it goes atop the spring so the caster-camber plate assembly can ride on it. Maximum uses sliding plastic discs in the perch (which allows the steering rotational movement) since finding the stock-type ball bearings died rapidly from dirt.

8. With the spring perch and caster/camber plate assembly sitting atop the spring and strut, the fun part is compressing the spring enough to get the big strut nut started. This is a non-issue with a spring compressor, of course. Pros in a hurry have found they can just barely compress the spring enough by hand if they are big enough and the spring short enough (stock springs are too tall for this trick).

9. With the nut started, it can be gunned down. The spring, strut, and caster/camber plate assembly is ready to go back in the car’s wheelwell. Don’t over-torque; Ford and Tokico struts take but 45 lb-ft on this nut. Bilstein or H&R struts need 54 lb-ft.

10. Before sliding the strut assembly into its pocket in the strut tower, make sure there are no dirt or metal scars on the bottom of the strut tower to impede caster/camber plate movement. A quick shot with a mini disc sander does the job. Finally, atop the strut tower goes the little kidney-shaped piece of advertising Maximum calls a support bracket. Now it’s time for an alignment.


Get It On

Caster/camber plates from Maximum Motorsports are one of the most popular Mustang bolt-ons and while often pro-installed, are a reasonable do-it-yourself job for enthusiasts with basic wrenching skills and air tools.

Fox and SN-95 installations ('79-‘04) are nearly identical, while S197s ('05-'13) differ somewhat. Most caster/camber plate installs are done in conjunction with lowering spring installs because the spring installation provides full access to the caster/camber plate, and typically lowering springs require caster/camber plates to regain tire-saving alignment specs.

All Mustang caster/camber installs require lifting the car high enough so the front suspension can reach full droop, plus room for a floor jack under the lower control arm. A sturdy set of tall jackstands is sufficient. A shop's hoist is maybe more convenient, but it is hardly a requirement.

While it's possible to install caster/camber plates without fully removing the strut from the chassis, practically speaking all Mustang caster/camber installs also require removing the front strut from the car. This means wrestling with the two large bolts securing the lower strut to the steering knuckle (spindle), along with handling the spring. It is possible to wrench the two strut bolts by hand, but they are torqued to 140-166 lb-ft depending on the application and are definitely less of a drag with an air gun.

Protecting your head from a partially unrestrained coil spring is a definite safety item, and if you are not well-versed in keeping a Mustang coil spring from flying around the shop either get help from someone who does or turn the job over to a pro.

In this story are installation highlights to give you a basic idea of what's involved, but they are by no means complete. Maximum Motorsports provides excellent caster/camber installation instruction booklets with each kit. These range from eight to 13 pages long, and can be downloaded as pdf's at www.maximummotorsports.com if you want to take a look ahead of time. Use these instructions! Maximum spends considerable time publishing detailed instructions, yet finds their number one problem is customers don't read or won't follow them.

Finally, the alignment must be properly set after caster/camber plate installation. Typically this means a short drive to a pro alignment rack, but Maximum offers an alignment gauge for track or home use. It makes sense for open-track drivers and racers.