Tom Wilson
May 2, 2014

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.