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Text and Photography - Jim Langley
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Ford has manufactured unibody cars for many years
and the Mustang has been a unibody from day one. The unibody design
has many benefits for a car manufacturer, the primary one being reducing
assembly cost. By having to only produce formed body panels there
is no extra cost of building a frame.
The unibody is also a lighter design then body on frame which needs less
power to move. This means smaller, less costly power plants, brakes
and suspension parts.
For a purely street driven car that is only a means of reliable transportation
this design is quite durable. Start adding power to that same platform
and pushing it hard in a racing venue and you will begin to reveal it's
limitations.
Hard launches at the drag strip or spirited 4 wheel drifts on the road coarse
will cause the unibody to flex far more than the manufacturer ever intended.
Continued hard use will result in bent, cracked or even torn suspension
mounting points. This flexing also degrades the handling of the car
since the suspension is moved away from the designed alignment.
So, for those of use that enjoy driving our cars much faster and harder
than Ford envisioned it is a good idea to reinforce that unibody before
it is pushed past it's limits!
In this article we will cover the four areas of opportunity for stiffening
the Fox uni-body platform; The Strut Tower Brace, The K-member Brace, Subframe
Connectors and Torque box reinforcements. |
Stage 1: Strut Tower Brace
Starting with the easiest, but highly effective, is bolting in a strut-tower
brace. If you've ever taken a box and opened up one side, you'll quickly
notice how weak the box becomes. This is analogous to what occurs in engine
compartment. The load and torque of the motor, combined with the constant
strain of the steering and front suspension, results in a very flexible
front end.
First the brace is laid in the engine compartment
to check for fit and clearances. On the drivers side the starter
solenoid needs to be moved temporarily- be sure to disconnect the
battery first!
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The wipers and cowl vent are removed to allow
access to the back of the firewall. The wipers lift off with
a little persuasion after the lock is moved back under each arm. The
cowl is simply held down with 6 Phillips head screws. Now is
a good time to touch up the vent and arms with some semi-gloss black.
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At the firewall the brace just touches the
BAP sensor, so the sensor is removed and it's mounting bracket clearenced
with a file. The passenger side bracket mounts without interference.
Once the bracket sits level the holes are marked for drilling.
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Once all six holes are drilled, start all six
bolts but do not tighten them until all of them are started. Be
sure to use the provided lock washers. We went a step further
and purchased some self locking Ny-loc nuts to replace the standard
nuts provided. |
By triangulating the strut towers and rear engine compartment bulkhead we
step closer to achieving a rigid "closed box" which eliminates
the flex and twist associated with an open engine compartment. This modification
not only results in a stiffer front end, but also reduces camber changes
under hard cornering.
The installation is straight forward As you can see from the photo,
the brace fits well, looks sharp, and only requires drilling a few holes
and removing the cowl vent for access.
The test drive after the install was downright shocking. The first
hard turn onto an on-ramp at speed resulted in almost hitting the barrier
as the steering needed less input than before and yours-truly oversteered!
Turn-in has been reduced significantly, meaning you don't have to
pull the wheel over as far when entering a tight turn with speed. Lane
changes and high speed maneuvers much more precise. If you make
no other changes to your Mustangs chassis, this is the best single performance
upgrade for handling you can make! |
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