Jam nuts necessary on LCA's?

I searched for an answer to this, but didn't find any. I installed Rusty's lower control arms, w/ adjustable ends. The ends screw into the arm about four inches or so, with fine threads. They come with a jam nut. I don't see the point of the jam nut. It seems that I'll have more flex with the two parts of the arm able to rotate around the threads. Since both ends are anchored in, there's no danger of the two halves working themselves loose, like there might be with a tie rod. So, I'm thinking of just leaving the jam nut off, or not tightening it up. Am I missing something? Below is a link to the arms so you can see what I mean.

http://rustysoffroad.com/mm5/merchant.mvc?Screen=PROD&Product_Code=RC-CA211-UV&Category_Code=ARMS

Without the jam nut, both ends of the arm will move in the threads eventually ruining the arms.

The threaded portion probably isn't built for constant rotation back and forth. I think they might wear too quickly and become loose. Obviously they won't unscrew, but eventually they would wear to the point where they could come apart.

Yes they are necessary! Like JBS stated the ends will eventually pull out because of they are constantly being twisted and pulled on. Tighten those suckers up!

Those control arms look sweeeet! The only bad thing I could see is the threads possibly wearing out over time if they worked back and forth a lot.

Looks like rapid consensus on this one!

Thanks for the reply. The only problem I could see was grit getting in there, and with teh constant rotation, it would wear enough slack in the threads to make the halves rattle, or eventually separate. You guys confirmed that. Thanks - I'll tighten them up!

The principle of operation for all of this stuff is that the inner and out metal sleeves are immobilized, and the rubber part of the bushing takes all of the rotation. This is the way stock is setup and the way aftermarket has to be setup too.

This is also why it's crucial to get the jeep to comfortable ride height before you torque everything down.

there was a thread a while back about somebody who installed some long arms, and was having steering/front end issues that he couldn't figure out. he thought jam nuts weren't important for the same reasons as you. those threads will have a small amount of axial play though, and beyond clunking, and making noise, you will eventually ruin the threads more then likely if you dont lock them down