Anyone on here built their own truck type rear suspension? I was wanting to use a coil spring, something like dirt track cars run. I know you would want a long panhard bar. I'd like to see some pics if you got them.
I looked into this awhile back. If I remember correctly the I beam style truck rear is intended to allow torsional twist in the arms when the suspension cycles. If I remember correctly, you will need to run heim joints if you don't use actual truck arms. Then again that was awhile ago...
This is a good youtube video that is exactly what your looking for . Posted using the Full Custom H.A.M.B. App!
You are correct. The GM 'truck arm' was designed to have longitudinal/torsional twist to accommodate chassis roll in relation to the axle when cornering. They were constructed as two "C" channels, back to back, approximately 14 ga material, forming an "I" beam cross section. The idea was to permit suspension articulation while still maintaining control of axle location and axle housing rotation. No matter how close to the driveshaft the leading ends of the arm are mounted, there is some twist induced on any but the flattest of turns or driveway entry, etc. This is often disregarded by builders, scoffed at even, with the common defensive claim "well, it worked for me". "Yes, but perhaps not as well as you think" is my answer. There is more to be gained, and nothing to be lost, by duplicating the GM engineered component form. The reverse is true of round, rectangle or square tube sections. I think there a couple of factors that enter into choosing tube stock.. First is likely a misunderstanding of the forces at work. Specifically, the need to twist; next is an over estimation of what it takes to control axle housing rotation on acceleration on anything but an drag car; lastly is, the tubes are 'quick and easy' to use. Sourcing good used original GM arms is not as easy in some places than others. Having them bent up on a metal brake from sheet stock takes bit more time and money. Reportedly, genuine NASCAR arms are available, used, from several race car parts shops. As for heim joints.........they will work, a "johnny joint" would be better, but again taking the cue from GM engineers, and industry practice, generous rubber bushings probably offer more benefits as to durability, weather resistance and isolating noise for street driven vehicles. There are numerous threads containing lots of discussion on this style suspension. Search "truck arm suspension" and/or similar wording. Ray
The Jalopy Journal
