Aluminum Control Arms - Why?

[DMopar97]

Hey Folks,
I've had a couple of '97 TJ's since early 2000's. One extensively modified with 42's, full hydro, dual cases, 1 tons, etc. Another mild built with 35's, arb's, 4:1, etc. Back in those days control arms were always made out of steel. In my case, I have all Rubicon Express joints on my steel control arms (home made, not RE arms).

I recently bought a bone stock 2005 LJ Rubicon (6 speed). It seems many double adjustable johnny joint control arms are made from aluminum these days. Why? What's the advantage?
My initial concerns with aluminum would be:
* long term, multi decade aluminum thread strength
* damage to the arm itself, both from sliding over stuff, and smashing into things.

I'm not the young dumb guy I used to be, who you'd be likely to find in the (sluice) box at 3am bouncing off the rev limiter... But I'm still a rock crawler. I mostly do Fordyce these days, and looking to spend more time in Moab. This LJ will be a streetable mild built rig on 35's or 37's with a 2-3" short arm lift, and flat belly. I may at some point build a custom mid arm lift, and Ideally I'd like to be able to re use the joints.

By the time I buy all the joints and bungs, there's not much of a cost difference between making my own steel arms, and buying aluminum arms. So I'm looking for feedback on why going with aluminum is the right way to go for a rig spending its time in the rocks. Thanks!

 

[Ir0nH3@d]

aluminum, when using the proper alloy and design, is every bit as strong as steel and has less deflection.

i choose aluminum (Savvy) due to living in a region that salts heavily in the winter and try to stay away from steel when possible. I have dragged them over boulders and got nothing more than a scratch. over a decade of use and have no regrets

 

[AndyG]

Should be a lot of guys who can weigh in-

I have aluminum on one and steel on another- no complaints either way.

Good post. You sound like the kind of guy that needs to be on here.

 

[mrblaine]

Hey Folks,
I've had a couple of '97 TJ's since early 2000's. One extensively modified with 42's, full hydro, dual cases, 1 tons, etc. Another mild built with 35's, arb's, 4:1, etc. Back in those days control arms were always made out of steel. In my case, I have all Rubicon Express joints on my steel control arms (home made, not RE arms).

I recently bought a bone stock 2005 LJ Rubicon (6 speed). It seems many double adjustable johnny joint control arms are made from aluminum these days. Why? What's the advantage?
My initial concerns with aluminum would be:
* long term, multi decade aluminum thread strength
* damage to the arm itself, both from sliding over stuff, and smashing into things.

I'm not the young dumb guy I used to be, who you'd be likely to find in the (sluice) box at 3am bouncing off the rev limiter... But I'm still a rock crawler. I mostly do Fordyce these days, and looking to spend more time in Moab. This LJ will be a streetable mild built rig on 35's or 37's with a 2-3" short arm lift, and flat belly. I may at some point build a custom mid arm lift, and Ideally I'd like to be able to re use the joints.

By the time I buy all the joints and bungs, there's not much of a cost difference between making my own steel arms, and buying aluminum arms. So I'm looking for feedback on why going with aluminum is the right way to go for a rig spending its time in the rocks. Thanks!

Play with a tube calculator to get some ideas of how resistant to bending different materials are. I like the one Rogue Fab has on their site.

Compare the safety factor to dial in the load at the center point. It explains the safety factor and what it means. In this comparison, I picked 4130 tube that most won't buy but it is stronger to a degree over normal DOM. 7075 links are common and easily acquired. I use Julene at Summit Machine. She takes very good care of her customers. To get the aluminum link, it just has to be cut to length and threaded. Easy. To build the DOM arm, you're buying two weld in threaded bungs, welding, and then you need the taps to clean up the threads. I've done hundreds of weld in bungs, anyone that tries to give you some BS method for fixing the threads after welding that doesn't involve taps, tell'em to fuck off. Taps work every single time without fail.

With the 7075, we pick up the strength of solid over tube without the weight penalty for solid steel round bar stock. It is also hard enough to slide over rocks just fine. You also pick up a weight advantage over steel tube with the solid aluminum bar. 2" x .250 wall round steel is 4.6 pounds per foot, 2" solid aluminum round bar is 3.7 pounds per foot.

2" 7075 is good for about a 36" arm on a lower, any longer and you should consider bumping up the diameter.

 

[mrblaine]

Should be a lot of guys who can weigh in-

I have aluminum on one and steel on another- no complaints either way.

Good post. You sound like the kind of guy that needs to be on here.

When I could get the already heat treated tube, I always did steel 4130. When that went away, I switched to aluminum. There are reasons to do both, there are reasons not to do one or the other. Mostly it is time based. In a hurry, I can do steel faster.