Building control arms for your custom application
Reference: Herzog

Building custom control arms isn't necessarily very hard. It is just a matter of taking your time and getting measurements right and knowing what you need for your application.

Attain your measurements by placing your axle under you vehicle exactly where you want it. Make sure the axle is centered and is the right distance from the frame as it would normally be when the suspension is all together at static ride height. Then measure from frame mount to axle mount (center of bolt holes). This will give you your overall length of the control arm.

Now you have to take into consideration the bushings used to mount the control arms. I use Rubicon Express large Super-Flex Joints (part# RE3792) at the frame side and large OEM Jeep rubber bushings from Rubicon Express (part #RE3701) pressed into 2.25" ID tubing.

When you know which type of bushing will work best in your application, take the working length of each one on both sides and subtract that from the overall length. If your overall control arm length is 36", and each bushing end measures 1.5 from center to end of casing, you must subtract a total of 3 inches from the overall length, giving you 33 inches. We now know the length that we need to cut our tubing.

When cutting the length of round tubing at 33 inches, add an extra 1/2 inch for each side. This will give you enough material on the tubing to notch it for a good fit around the bushing casing. This extra material brings our cut up to 34 inches. The tubing used in this tech article for these control arms is 2" OD x .25" wall 1026 DOM tubing.

Notching the ends can be done several ways. These were notched using a 7" disc grinder. Be sure to only go 1/2" deep on each side. This will give you the 33" working distance from bushing case to bushing case. Make sure you notch both ends according to your bushing rotation and placement for the suspension bracket. Once the notching is finished, line up the bushing cases using a square and good judgment. Then tack weld them into place.

Once you have one of the sides lined up and tacked on, place the arm on flat ground and square up the next casing to tack on. The flat ground will ensure that both casings are in-line with each other. Lay a square down next to the arm, line up the casing and tack weld it on. When both ends are tacked on, retake measurements to make sure they are square.

When you are sure that you have both ends lined up properly, weld them on solid. If you don't trust your welding for suspension components, have an experienced welder do this for you. Any additional mounts on the arms may be made. Be sure to let them cool SLOWLY after welding. Do NOT quench the hot welds.

When the arms are completely cooled off, the bushings may be assembled and/or pressed in. First we did the RE Spherical joints. These joints are very easy to assemble, be sure to use plenty of grease in these casings. Make sure to tighten the casing shims tight enough to prevent premature wear or failure and to keep dirt and water out.

After the RE joints were assembled, I pressed the OEM rubber bushings into the 2.75 OD, 2.25 ID, .25 wall casing at the other end of the arms with a 20 ton shop press. These bushings have a stepped ridge at one end and is impossible to beat in with a hammer. A press makes short work of installing these bushings.

And now we have a complete set of lower control arms.