5.0 Mustang & Super FordsHow To Chassis Suspension
Maximum Motorsports Suspension Setup
You've bolted on your new Maximum Motorsports suspension--here's how to set it up for the first time
Followers of our open-track project car know we've previously detailed the installation of nearly the entire Maximum Motorsports catalog on our "stripe" car. Torque arm and Panhard bar; K-member and lower control arms; springs, shocks, and adjustable sway bars; subframe connectors and strut-tower brace; caster-camber plates--you name it, we've got it.
This month we're not bolting anything on the car; rather, we're doing the last bit of shop work associated with installing these hard-charging suspension bits--setting them up. That really boils down to aligning all the suspension parts and getting them square to each other so the car runs straight and the suspension moves in symmetrical arcs.
Nearly all this setup work is new to most Mustangers. In fact, it has basically been the domain of dedicated chassis specialists. But while the terms and procedures may seem foreign, they are absolutely required when installing a torque-arm-and-K-member-type suspension.
For chassis setup, a level working area is a must because a few key set-up steps use the ground as an assumed level starting point. By level, we mean truly level, an area where a bubble level will at least try to keep the bubble inside the target window. Typically a smooth concrete garage floor will do the job.Furthermore, besides having this level spot to work off, you'll also need some way of supporting the vehicle at an under-car working height, but still with the car sitting on its tires, and still level. It can be something of a trick unless you have four platform stands (typically custom made) or a dual ramp-type hoist as preferred by transmission shops. Chassis shops prefer the platforms, as hoists typically cover up too much under the car to be convenient.
What You're Doing
Chassis work is one of those abstract subjects that takes 10,000 words to describe but comes quickly once you have the parts in front of you. Having a limited number of words at our disposal, we can only touch on the brightest highlights of setting up the Maximum Motorsports gear here, but be advised their installation instructions are comprehensive, probably some of the best in the industry. To get started, here are the required jobs, in order, for chassis setup.
1) Configure the car as it will run (half tank of gas, empty trunk if a track car, and so on).
2) Square the K-member side-to-side.
3) Center the steering rack on the K-member.
4) Center the moving portion of the steering rack relative to the rack housing.
5) Set the ride height.
6) Square the rear axle to the rear control arm pivot bolts.
7) Square length-adjustable rear control arms in the second plane.
8) Set pinion angle.
9) Set camber, caster, and then toe.
10) Bumpsteer the front suspension.
11) Reset the toe.
12) Scale the car with driver.
13) Reset the camber with driver in the car.
14) Recheck the toe.
15) Adjust the sway bar end links so there is no preload (with driver in car).
Obviously, this is a considerable amount of work. Luckily, most of it need be done only once. For example, after the K-member, steering, and so on are square to each other, they won't move unless swatted heavily in an accident, so you won't have to worry about them as maintenance items. However, as with any car, setting the alignment (caster, camber, and toe) needs to be done occasionally. Furthermore, if yours is a track car, you may wish to fiddle with corner weights and alignment depending on track configuration. That's fodder for another article, so we'll cover that next time. Now that we've outlined the jobs, let's get to the details.
Configure car as it will run.
Weight and ride height are important to getting the new suspension parts precisely located. Therefore, the car must be configured to how it will normally run. For track cars, this means removing any items normally not used at the track. This is always the spare tire, jack, lug wrench, and so on, and maybe even the passenger seat. Maximum likes to run Mustangs with a full tank of gas to put weight over the rear axle, in which case the gas tank should be full. Use the correct tires and inflation.
Setting up a street car is more fraught with compromises, because you may or may not run with passengers. Do what you can. Most people still set up the car for just the driver, and street/track cars should be set up for where it is most important. Ours is a track car that can venture onto the street in search of the next track, so it gets aggressive alignment settings. Most owners will be happier with less extreme settings.
K-member squared side-to-side.
The new K-member must be installed squarely relative to the rear axle. This is because the K-member locates the front suspension, and you definitely need the front wheels square to the rears!
The technique is to measure from the K-member's lower-control-arm mounting holes to the rear lower-control-arm pickup mounting holes on the chassis. This is done both front-to-rear and diagonally.
As it is quite awkward to measure directly between these points, it is best to attach a plumb bob to the pickup points at the rear and mark a spot on the ground. Then the plumb bobs can be hung from the K-member and measurements taken between the marked points and the plumb bobs. Marks on the ground have the advantage of not swinging around like a plumb bob, which always happens when someone bumps the car or after kicking the plumb bob while thrashing around under the car. Furthermore, you need only two plumb bobs this way.
By just snugging the K-member mounting bolts, the K-member may be "adjusted" with a rubber mallet, prying, and so on until the K-member is square to the rear suspension.
Center steering rack on K-member.
Because the steering rack is mounted on studs projecting from the K-member, this step is all about ensuring any offset rack bushings are set up perfectly straight up and down. In other words, you want the "pupils" in the offset "eyes" to be right at six o'clock, not wobbled around like Moon Eyes. This is done with straightedges and bubble levels, the only complication being the steering rack is always in the way, so you need to use the straightedges to move the bubble level out into the clear.
As an aside, life is easier here if small marks are made on the outer edge of the offset bushings before the bushings are installed. These marks should indicate the centerline of the bolt hole in the bushing. Since the bushings are visible after the rack installation, a simple check with a straightedge and level will quickly tell if they are straight up and down. It's a pain to nudge these bushings around, but even if you have to pull off the rack to get things equal, it's necessary to get the bumpsteer the same side-to-side later.
Center moving portion of rack to rack housing.
OK, the idea here is to center the steering rack relative to the steering-rack housing (the aluminum casting). Combined with the previous step, this will put the inner tie-rod ends symmetrical side-to-side in the car for bumpsteer purposes. In reality, this step is almost always a check against someone having removed the steering wheel and replacing it a spline or two off on the steering shaft. With airbag-equipped Mustangs, this is a rare thing; with earlier non-airbag cars, it happens when a lazy alignment technician decides to move the steering wheel on the shaft rather than center it using the tie-rod-end adjustments.
To center the rack, center the steering wheel by turning it lock-to-lock and then taking it halfway in between. While under the car, measure how far the rack protrudes from the rack housing. Be careful not to include the outer tie-rod ends in this measurement as they are adjustable and are bound to be dif-ferent lengths.If the steering rack is not centered, center it using the steering wheel, then remove the steering wheel and replace it in a square position on the steering rack.
Set ride height.
Coilover-equipped cars such as ours have easily adjustable ride height. By rotating the spring perch collars around the threads on the outside of the shocks, the coil springs can be raised or lowered, thus changing the height of that corner of the car.
Cars with stock-type coil springs require a height adjuster--commonly available for the rear springs--to change the ride height.
Clearly, the car must be supported on its tires for this task. The idea is to ensure the suspension is supporting the chassis level with the ground. This is important with the Panhard bar, as the bar swings in an arc. If the car isn't level, the arc will be different in suspension compression and extension.
The ride height should be set with the passenger load expected for the Mustang's normal duty, which typically means two people for street cars and just the driver for track cars. But, if you commonly give track-based thrill rides, then you might want to set up with a passenger.
Square rear axle to rear control arm pivot bolts.
Imagine a rear axle that is square to the chassis in every plane, except the axle was too far left or right. In other words, viewed from directly behind the car, the left rear tire was buried far inside the wheelwell, while the right rear tire was hanging out in the breeze. By adjusting the length of the Panhard bar, the axle can be centered relative to the chassis. You can also check the Panhard bar height now; it should be parallel to the ground.
Measure from across the tire to the lower control arm front pivot. Use a straightedge across the wheel to get a square measurement. Sometimes the tire protrudes from the rim, in which case you can measure off the tire, but beware the straightedge doesn't end up in the seam in the tire sidewall. You can feel the seam with your fingertips--it's a small indentation, and sometimes you can even see it. When adjusting the Panhard bar, also loosen the torque arm crossmember mounting bolts so the front of the torque arm can shuffle along with the axle as it moves sideways in the chassis.
Squaring length-adjustable rear lower control arms.
Imagine looking down on the rear axle in plain view using your Superman X-ray vision. If the axle is cocked sideways relative to the chassis, the car will dog-track down the highway and exhibit different turning characteristics left-to-right.This relationship is adjustable if you have adjustable-length control arms. Simple tape measurements will tell the tale and turning the adjusters will move the axle.
Set pinion angle.
By design, torque arms set the rear pinion angle. This is fine-tuned with the Maximum Motorsports torque arm with shims placed between the front of the differential and the torque-arm mount. The pinion angle is measured using a straightedge and protractor, both at the differential flange and at the transmission. The straightedge is necessary only to transfer the measuring surface away from the crowded torque-arm-driveshaft-differential interface. In the photo, the point where the shims go is just behind the measuring device.
Camber, caster, and then toe.
Racers and chassis enthusiasts use small, handheld, bubble-level devices held against the front wheels to measure the traditional front-end alignment values of caster and camber. The toe is set by measuring the front and rear of the tire centerline relative to a known distance marker. Traditionally this distance marker is a length of string rigged to run along the side of the car.
We don't have enough room here to detail the installation and use of the string or the caster/camber gauge, so we'll leave that to the Maximum and gauge manufacturer instructions. We can note, however, that the string is easily set up once you have some small stands or tripods dedicated to the task, along with a length of contractor's string. The actual suspension adjustments are done with the caster/camber plates and tie-rod ends as always.
In the photos, you might see a white triangle. It's a piece of card stock Maximum cut to a 20-degree angle. Set against a known straight line scribed into the platform stand and then turning the tire until the sidewall is aligned with the 20-degree side of the card stock, this simple device allows accurate measurement of the camber at 20 degrees of steering.
Ah, the mysterious bumpsteering process. It would take an entire article to detail bumpsteering a front suspension. In a nutshell, the process involves measuring the amount of toe change the front suspension goes through as the suspension is cycled through its travel, then doing what you can to reduce the toe changes to a minimum.
The toe changes come from the geometry differences between the steering and the rest of the suspension. The usual culprits are the outer tie-rod ends and how they are angled relative to the steering rack at one end and the steering knuckle at the other. While we tend to think of the tie-rod ends as the bad guys, they're simply caught in the middle of a bunch of other parts. But that's where bumpsteer thinking usually centers.
Bumpsteer adjustments are made by adjusting the height (typically lowering) of the tie rods where they mate with the steering knuckle, using bushings or washers. Pushing the steering rack around with offset bushings is also useful, and swapping spindles can help as well. Luckily, most of this is taken care of by the mounts built into the Maximum K-member and so on, so only fine-tuning of the bumpsteer is necessary. You want to go to the trouble, as too much bumpsteer makes the car less predictable whenever the suspension moves up and down. It is often felt as imprecision, vagueness, or nervousness in the steering.
Measuring bumpsteer is actually a specialized form of measuring toe. As you can see in the photo, Maximum uses a humble but accurate bit of plywood and a dial indicator to measure the toe while the suspension is jacked up and down with a floor jack (the spring must be removed or slacked so just the suspension moves and not the entire car).
After fiddling with the bumpsteer toe changes, the static, baseline toe may have wandered off somewhat, so it is rechecked at this point.
Now it's time to find out how much weight each corner of the car is carrying and try to even out those weights. There is only so much that can be done with a front-heavy production car such as a Mustang, but every bit helps as the tire contact patches are most efficiently employed when the weight is evenly spread.
The job is to set the car on level ground on four scales (one under each tire). All suspension preload must be removed, so disconnect one end of each sway bar and adjust the tire pressures. Have the driver sit behind the wheel (with helmet, if that's how the car is run), and then read the corner weights.
Specialized four-pad scales for this purpose are widely available from racing supply houses. That's what Maximum uses, but you can do the job with any sort of scale that will take the weight--our '96 GT had 1,014 pounds on the left front tire--and can be practically employed without upsetting the level too much.
Coarse adjustments are made by moving components around the car (relocating the battery to the right rear corner). Fine adjustments, as are being checked here, are done by changing the preload on the springs. This is easily done with coilovers.
Most of the time, an even set of corner weights is desirable. However, some tracks have a particularly large number of either left or right turns, or one turn that is especially difficult and important to lap times. The weights may be skewed to favor those conditions.
With driver in car, reset camber.
OK, now we're gilding the lily. This step is only necessary at this point on fine-tuned road-racing cars. Street cars and almost all open-track cars can skip this step.
Everybody, however, should recheck the toe.
Adjust sway bar preload.
With the driver still in the car, reconnect the sway bars, making sure there is no preload on the links. That is, the end links should swing freely onto the sway bar so there is no load on the bar while the suspension is in its neutral position. With Maximum's adjustable rear sway bar, this is simply done with the turnbuckle-like ends. The stock front sway bar is adjusted when wrenching down on the end links.
Well, that's the bum's rush on adjusting a newly installed Maximum Motorsport suspension. The majority of this work is done only one time, as the event-to-event and at-track adjustments are typically limited to checking the alignment--especially the toe--and working with shock tuning and spring preloads. Or, if you're like us, you have so much fun driving the blasted thing you won't even stop for lunch, much less adjusting things! 5.0