Performance Suspension for American Muscle Cars

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1994-96 Impala

Rear tubular lower control arm tech and why we build them the way we do. 

 No bind is our motto when it comes to suspension. Most rear control arms bind during suspension movement at one point or another. The factory system is compliant but suffers providing control. We tested several apposing angle rear suspensions found on many GM vehicles and found pretty simple and yet surprising information. First  if you try and use solid type  polyurethane or Del-a-lum bushings on both ends of the control arm a bind condition will occur. One end of the control arm must be able to pivot. That is why our rear lower control arm kits use a spherical bearing installed on the frame side. Second if you put spherical bearings on the upper control arm and mimic the bottom control arm you would have full suspension travel with no bind. No I'm afraid not.  In fact we put bearings on both ends of the control arm and still ran into suspension bind. How is this possible? The upper angles are so acute that there is not enough movement in the spherical bearing to accommodate full suspension travel. You will run out of bearing compliance going over severe bumps and if you are in a turn and go over a bump, no doubt the rod end will run out of compliance. A bind condition will occur.

GM's design works like this. The upper control arms are placed at an acute angle in order to provide lateral control for the rear end. They also support pinion angle. The lower control arms are considered followers. When suspension movement occurs such as over a bump, the rubber bushings begin to twist. Even though rubber bushings allow for some movement. They reach a point where they will increase resistance and become less compliant. Once the bushing reaches this point the control arm flexes allowing the finial movement to be carried out. Since the rear suspension is built with conflicting angles GM uses the flex in the control arm to full fill the finial movement. This also keeps the rear suspension compliant without going into complete bind and reduces ride harshness. Removing the ability for the rear suspension to be compliant will cause a suspension bind at one point or another.  For example boxing the upper control arms is something I would not do unless I wanted to create a rising rate rear suspension.

Here is how we approach the problem. We build a spherical bearing and Del-a-lum bushing lower control arm. The arm is pre-assembled and has provisions for a sway bar. Del-a-lum bushings are installed on the rear side and the spherical bearing goes on the frame side. We leave the upper control arm alone and use stock upper bushings.

How the rear lower arm works!

 First Del-a-lum bushings do not allow lateral movement. The combination of inner and outer thrust washers plus the inner rotating sleeve make the bushing act like a bearing in a straight up and down application. Lateral deflection is not allowed. The bearing on the other end however will allow rotation in all directions. Now this is the key, since the lower control arms are placed at opposing angles (not as sever as the uppers) and by placing the Del-a-lum bushings on the rear end side with the bearing of the frame side, lateral movement of the rear end is now controlled by the lower control arms. The upper arms no longer perform that job and since the lower arms are positioned out by the tires, the cars rear end becomes stable. The bearing allows for full rear end movement without bind. 

 At this point there are no upper rear control arms that we have seen on the market capable of maintaining full suspension movement without going into bind at one point or another. We produced similar upper control arms for testing purposes and found only one way to do it. Nobody produces it. This item will be produced by us in the near future however until then we will recommend using stock uppers.

 

 

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Additional features are
* Spherical bearing on the frame side.
* Del-a-lum bushings on the rear end side.
* Easy access grease fittings for lubricating the rear bushings.
* Support tubes for the sway bar bolts are welded in the control arms.

Part # TBC-12 is a no nonsense rear lower control arm. Built out of 2 inch diameter round tubing and uses a 3/16 support plate for the sway bar.  TBC-12 strength and reliability surpass the traditional tubular lower arm. Bolting on these lower control arms will provide corner exit and straight line stability without sacrificing comfort.

Cost # TBC-12 -- $356.31 pr

 

Bushing kits:

We offer several types of bushings: rubber, polyurethane, brass, and Del-a-lum (pronounced della-loom). Unquestionably Del-a-lum bushings are the Top of the line when it comes to suspension control and longevity. They will out last all the other bushings listed. In fact Del-a-lum bushings come with a life time warranty to the original purchaser. No other bushing has a warranty that strong. We have been using Del-a-lum bushings for over 20 years and to this day warranted only a hand full of bushings. They last from 120,000 miles to 320,000 miles. These bushings are approved for all NHRA and are excellent for street, road race, and dirt track applications.

Upper bushing kit Part # 1016  --- cost $125.34
Lower bushing kit Part # 1020 ---- cost $150.41

 

Tubular Tie Rod Adjusting Sleeves Part # ADJ-3 replaces the standard split sleeve tie rod adjuster located between the inner and outer tie rods. The sleeve is stronger then  stock  mainly because of full thread engagement. The tie rod sleeves features machined slots designed to except an open end wrench for easy adjusting. Gold zinc finished for rust prevention and right and left hand jam nuts make this kit an easy add. 

 ADJ-3  Tie rod sleeves  ---- cost $51.26

 

Impala's are notorious for being under sprung in the front end. An increase in the front spring rate department is required for obtaining  cornering ability. Global West's part # S-81 does exactly that. Not to much on the spring rate to create a ruff ride, but just enough to make the car respond. 

S-81 springs will lower most Impalas slightly, about 3/4 inch. However Impalas had three different springs available. All giving different ride heights.  You could have the lowest spring ride height available and the S-81 would not lower it quite as much. 

 Part # S-81 -Cost $166.18 pr

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