Originally Posted by Wannafbody
At what point is one needed? A certain weight or a certain trailer length?
Weight, not length. 500 pounds tongue (hitch) weight or more requires a WD hitch. And if you buy a cheap WD hitch that does not have built-in sway control you should be taken out at sunrise and shot.
Industry jargon is confusing. They say any trailer that grosses over 5,000 pounds or has a hitch weight of 500 pounds or more requires a WD hitch. But most TTs and other tandem-axle trailers have loaded hitch weight of 11.5% to 15%, so you will exceed 500 pounds hitch weight before you reach 5,000 pounds gross trailer weight. If a trailer has 15% hitch weight, then the max weight of any tandem-axle trailer you should tow with a weight-carrying hitch is about 3,333 pounds. So instead of the simple 500/5,000 max for hitch and trailer weight, I use a more accurate 500/3,333 max.
Go for a Reese Straight-Line WD hitch with dual-cam sway controls built in, or an Equali-I-Zer brand hitch which includes built-in friction type sway control. Or if you want the best sway control available, then go for a ProPride hitch.
As the ProPride website shows, the ProPride will cost you $2,345. A Reese Straight-Line trunnion-bar hitch complete with shank or an Equal-I-Zer will be less than $600.
To muddy the water a bit, you might want a sway controller even if your trailer doesn't have anywhere near 500 pounds hitch weight. In my case, I have a 5x10 golf cart trailer that I tow behind a 5er. The wet and loaded trailer weighs about 2,500 pounds, with hitch weight about 300 pounds (12% hitch weight). But when the 5er does a bobble, the second trailer does a huge sway. So I use an EZ-Lift friction sway control bar to control the sway on the golf cart trailer, even though I don't tow it with a WD hitch.