|
| |
The Mustang suspension is based on a design
originally used in the Ford Falcon. It has some definite limitations that need
to be addressed for performance usage. The biggest problem is the
backwards factory camber curve. Basically, as the suspension compresses, the top
of the tire tends to tilt "out" (positive camber). This promotes
understeer, which is consider "safe" for normal use, but nowhere near
optimal for performance usage. The second problem is "bumpsteer",
which is the toe change the occurs as the suspension moves thru it's vertical
travel. Bumpsteer becomes even more pronounced with suspension component changes
(spindles, a-arms) and with lowering. There are basically two schools of
suspension thought:
- Stiff (620#+) springs, limiting suspension movement to mask the bad camber
curve.
- Soft springs, let the suspension move, and modify components to change the
camber curve.
Either school has it's advantages and disadvantages, depending on the
environment it's being used in. A relatively smooth racetrack is a MUCH
different environment than that which a street car will operate. As our car is a "street" car, we used
the second approach.
 | Upper A-Arms. The upper a-arm is "the" key component in
the Mustang suspension, and there is SO much that can be done in this area,
that we've now created an entire "Upper A-Arm sub-page" to cover
it. Link button is on the left. |
| Spring Perch. The spring perch is mounted on the upper a-arm, and
provides a mounting point for the front coil spring. In stock form, it uses
a rubber bushing to help isolate vibration. However, that bushing tends to
bind as the perch swivels during a-arm movement. Some urethane-bushed
perches also bind. We were able to find free-swiveling urethane perches from
NPD, and have used them for a couple years now with no problems. Perches
with swivel bearings are also available from Cobra Automotive - while
somewhat pricey, they are the ultimate for smooth movement. Spring perches
can also be home-modified with either bearings or fabricated Delrin bushings
with grease fittings.. |
| Coil Springs. For a street car, I strongly prefer springs toward
the softer end of the scale (443#, 480#, 520#,540#). With proper suspension
geometry, we can leave the springs softer, and let the suspension do it's
job. If you're trying to mask the bad camber curve, then stiffer
(620#,720#,750#,900#) springs are one way to help do it. You'll pay the
price on cross-county drives though! |
| Ride Height. To get the best camber curve, you're looking for the
lower control arm to be within 1/8" of level, when measured from the
centerline of the inner pivot to the bottom of the spindle. For most cars,
this ends up being 1"-1.5" lower than stock. Always install the
springs uncut, check, trim 1/4 coil at time, and repeat as necessary to get
this spec. Further lowering should be evaluated via design drawings, as the
roll center and camber curves can be adversely affected by the extreme control arm angles
created. |
| Shocks. Put the best shocks on that you can afford. We're running
Cure-rides, which are basically a half-step down from Koni's. The
Edelbrock's are quite popular also, and their design reduces unsprung
weight. Spax shocks are externally adjustable, but some have reported
quality problems with them. The KYB's are very price-competitive, but tend
to be very stiff. |
| Lower A-Arms. They're just "along for the ride", right?
Well, not exactly. During vertical travel, they do locate the lower end of
the spindle fairly easily. However, when you hit a pothole, bump, or
curb(!), it's the lower arm that takes the biggest hit. If you can't do the
strong tubular arms here, at least consider adding a reinforcement plate to
the stock lower arm to "box" it in. The Global West arms we use
have the lower plate as well as a spherical inner bearing, which helps
eliminate binding at that location. The lower arm and strut rod do not move
in the same arc, which can produce a surprising amount of bind, even with
soft rubber. It's best to stay away from urethane
bushings here also, since they tend to bind in this location. |
| Strut Rods. The strut rods triangulate the lower arm back to the
frame. They also have to absorb a lot of impact force. Aftermarket
adjustable strut rods are seeing more street use, and are much stronger than
the stock strut rod. In addition, they allow some amount of caster
adjustment at the lower arm. It's best to start with the arm square to the
chassis, and only adjust the strut rod length if sufficient caster cannot be
obtained thru upper arm adjustment. Be sure to adjust both sides equally,
otherwise you can end up with different bumpsteer, camber, and Ackerman
curves on each side of the car. The primary benefit of heim-jointed strut
rods is not in the adjustability, but the smooth, non-binding movement, and
solid locating. Really
Good Adjustable Strut Rod Link! |
| Strut Rod Bushings. DO NOT use urethane bushings at the front of
the strut rod - instead of absorbing the impact forces by compressing, they
cause the strut rod to absorb more of the force, often leading to breakage.
We have had some success with rubber bushings in front of the strut rod, and
urethane behind the frame mount. Aftermarket strut rods eliminate the
bushings altogether. |
| Sway bar. The stock 5/8" sway is completely inadequate.
Replace with at least a 1" bar. The sway bar is a tuning aid, and
larger (or slightly smaller) diameters can be used to fine-tune the
handling. Rear sway bars are the same way - use them for fine-tuning, if
your car requires it! |
| Chassis stiffening. The front unibody of the Mustang moves more
than you would believe. An Export Brace & Monte Carlo bar are MUST-have
items before you do anything else! Adding torque boxes and subframe
connectors are high on the list also. Strongly consider solid welding floor
pans, seat risers and other sheetmetal in place of the factory spotwelds. |
| Weight. Anything you can do to remove weight from the car,
especially in the front, will help improve handling. We've gone to aluminum
heads, intake, water pump, etc., in addition to a fiberglass hood, and
relocating the battery to the trunk. We've taken approximately 200 lbs off
the nose, while adding a few in the rear of the car. |
| Spindles. While the "Granada brake swap" has many fans,
I'm NOT one of them. The spindle IS slightly different (under 1/4") in
the steering arm location. This is difficult to measure, but if they were
EXACTLY the same, you could bolt them on without adjusting toe. You can't,
as the front end always ends up toed-in, and I've heard plenty of stories
about running out of tie rod thread adjustment. Our own experience with them
was expensive and troublesome (read it in the "Our
Story" section). For applications with unmodified geometry and/or
stiff springs, you can get by with them. Anytime you swap spindles, I highly
recommend checking bumpsteer - it can be quite surprising! |
| Bumpsteer. We've added a separate page to cover bumpsteer. Link
button is on the left side of the page. |
For further reading, there are links to several good suspension articles on
our Suspension
Tech Links Section as well as a Suspension
Vendors Links Section.
|
