When a car leans in a curve, one end of the rear axle is moving upward relative to the body while the other moves downward and both ends are moving in arcs. If both ends of each of the four control arms are solidly bushed, bind is created. But if the soft factory rubber bushings are in place, there’s so much deflection that the wheels hop on hard launches, and in corners the whole damn rear axle will move horizontally as well as up and down, relative to the body. That‘s what creates the tail-wagging-the-dog sensation most Mustangs (and other Fox-platform) owners know all too well. The suspension engineers at Global West Suspension have taken a different approach to taming the late model Mustang’s well-documented rear suspension shortcomings. The Mustang’s lower control arms govern the rear axles up and down movement, as well as keeping it located fore and aft. The upper control arms serve to locate the axle and allow it to move in the aforementioned arcs. The soft factory lower arm bushing allow too much uncontrolled movement, both to the sides and fore/aft, but solid type bushings eliminate all compliance, which means the arms bind every time the axle moves any way but evenly up and /or down. The Global West Suspension TBF-series lower control arms feature their patented Del-A-Lum bushings at the axle-end of the arm and an aircraft grade spherical bearing at the frame/body end. The Del-A-Lum bushings eliminate control arm deflection, while the aircraft spherical bearings at the frame side attachment points both eliminate deflection and the same time allow the arm to rotate as the suspension moves in its arcs. Global West Suspension recommends against using custom or rebushed upper control arms with their TBF-series lower control arms. When we test drove the 5.0L Mustang that received the Air Locker 8.8 rear end, we could immediately feel the improved control and response that the Global West Suspension TBF control arms imparted. These arms are pricier than most, but they work great.

This portion of a article was published in FORD HIGH PERFORMANCE MAGAZINE, APRIL 1997
BY BOB WALLACE

From Global West:

A few words about rear lower control arms..... One of the biggest mistakes a person
makes is to put on a set of lower control arms that use polyurethane or poly-graphite bushings!
If the car is going to be used as a drag car and not used on the street. We have found it would be
an acceptable situation. However, when polyurethane is used on the street or for road racing
application, the suspension takes on a tremendous amount of bind. Many people interpret
that tight feeling as something desirable, but in fact, what they are really feeling is the suspension
binding up which in turn, can cause an oversteer condition. The car will also have a tendency to
unload the inside rear tire when going through a turn.

BIG PROBLEM:
If both the upper and lower control arms are fitted with polyurethane bushings, the situation gets
even worse. NOW, you have eight suspension pivot points in bind instead of four.

The bottom line is this:

Polyurethane, polygraphite or any other material that does not allow proper rear end
movement including muti-poly bushings will put the suspension in bind!

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