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The stock arms in the Camaro are pretty soft overall. The factory arm is steel stamping with a preloaded rubber bushing at each end. The arm is an open section with the bushings pressed into the steel arm. When accelerating hard over any ruts or bumps, the rear suspension feels like it is jumping around as traction is lost and regained. I felt it was a simple and important upgrade to stiffen the arms on my car.
Lower arm removed from car
View of open section
View of Bushing - The bushing is pressed in place and grips the arm at each end.
Plate Prepared for Welding
The plate is 2" wide 1/8" mild steel. The V notches at the ends are added to make the plate stiffness taper off over a short distance rather than ending abruptly. Note: The V shape has a 3/16" radius at the root of the "V" so that we do not create a new crack initiation point. The transition from full box section to open section at the ends is more gradual. Sudden changes in stiffness creates localized high stresses and the goal is the strengthen the arm, not weaken it. The plate stays clear of the ends to allow access for tooling when switching the bushings. There is no real need for the arm to be any stiffer since the bushings are so much more flexible than the steel arm.
I left the stock bushings in place while doing the actual welding in order to prevent the arm from twisting. I tacked the plate down in multiple places along each edge before doing anything resembling a seam weld. Even then I did not weld anything longer than 2 inches in one go, again to minimize any distortion.
Pressing the new bushings in
View of proper pressing method
Bushings must be removed properly or you will crush the arm flat. You can see two half circle pieces inside the arm surrounding the bushing. These pieces keep the arm walls at the right distance while pressing. At the bottom a 2" socket acts to receive the bushing as it protrudes through the arm. At the top is an aluminum tube just large enough to press on the bushing's outer shell. Removal of the bushing is just the opposite of the installation but with a receiver large enough for the wide flange of the bushing to enter.
1LE Bushing in place
My 1987 Buick Grand National used the exact same LCA as the 4th generation F-Body, you can swap them. I did this exact same upgrade in the Buick. In that car the factory used solid rubber bushings like the 1LE bushings but the rubber was much softer. It is very hard to deflect the rubber on the 1LE using your finger nail. The Buick bushings deflected quite easily. It probably is not that important to actually use the GM 1LE part. The standard Moog replacement bushings seem to be the same rubber hardness. I used the GM 1LE bushings here because I got them for a good price. In the Buick, the increase in LCA overall stiffness was quite a lot due to the differences in the rubbers used.
In the case of the Camaro, the factory used the bushings shown below. The rubber appears to be no less stiff than the 1LE bushing but the gaps where the rubber is missing does allow for more rubber flex even along the axis of the arm. Rubber changes volume very little when strained so it expands into the empty gaps when squeezed. The solid rubber 1LE bushing therefore adds more stiffness than might be obvious at first glance.
Why did I go the route as shown above and not just buy some aftermarket arms? Well, a lot of people make the assumption that OEM parts are the crappy result of corporate penny-pinching and that nearly any aftermarket replacement part must be an improvement. Keep the following in mind:
The OEMs have to certify cars to meet certain standards, in particular suspension pieces must meet endurance standards. The aftermarket guys cannot actually tell you its safe to use these pieces on a public road. There are 2 reasons for this, the aftermarket guys do not have the expertise nor have they had the parts certified as a form fit function replacement for the stock parts.
Technically, those aftermarket arms probably are not legal without some form of certification!
The stock replacement parts companies (eg. Moog, Wagner, Bilstein) have the resources to certify parts and for most part also provide parts to the OEMs.