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Text and Photography - Jim Langley

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!

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.

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.

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!
 

In This Article...
FordMuscle shows you easy and effective suspension tips for your 5.0L Mustang.

 
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