I posted this as a reply to a particular post and thought it good to post independently. Enjoy.
Everyone can easily experiment on their own motor home's rear sway bar very simply to determine effectiveness. While parked, have an adult family stand inside the motor home over the rear axle, facing forward. Have them try their best to rock the rig side to side by shifting their weight left to right. An effective rear sway bar will lower both rear corners simultaneously regardless which way the weight has shifted. If you had no rear sway bar, one corner would raise up when the other rear corner went down. You can sight it best looking at the relationship between the rear tire and RV body.
A lesser rear sway bar would still lower the opposing rear corner, but not as much as a heavy duty bar would, hence you will still feel the rig rocking.
You could also perform this experiment on the front axle but because people can't stand directly over the front axle, you might not be able to get the right rocking motion to see the results. Still it would be worth a try.
When I perform this experiment on the rear of my own rig with Roadmaster heavy duty sway bars, I feel the entire rear of the motor home drop regardless of my shifted weight. I simply cannot get the rig to rock side to side. It gets cancelled out by the lowering of the rear of the rig by some amount.
I suppose if you loaded up your rig with a pile of people trying to rock the rig in unison, you would create an extreme condition. I would imagine there is only so much any sway bar can handle.
