I am in the process of maknig a set of sliders, I got to looking at the designs out there from the manufacturers and i am wondering why there is a second bar on the designs?To me it seems easier to have just the single tube with outriggers to the frame. Does the second tube do anything particular for protection? I am thinknig mainly a step, but with the added weight of the extra tube i would think stay with a single. I know to each their own, but i am curious about the evolution of the slider design.

 

Overall rigitiy. And the added weight is hardly noticable...
Also, the farther they stick out, the more protection you have.

 

Thats how far i have mine sticking out. The inner main bar is right underneath the door frame, and the outer bar sticks out which helps as a step, protection of the doors.

 

The inner tube helps protect the pinch weld seam of the rocker panel and when the slider flexes upward under load, it'll make contact with that pinch weld to support the weight of the vehicle. Also, you generally need to come out horizontal from the frame to that point, then can angle upward a few inches for the outer bar, giving a little more ground clearance: