Cause and Fix for Sway from Boat Trailer Towed by 5th Wheel Trailer  

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In a tandem towing application, meaning pulling one trailer with another trailer, sway is common. If you happen to have a bass boat, which is much heavier in the rear due to the engine's weight, the sway problem will be especially noticeable. Any trailer tows best when it has the right amount of tongue weight (TW), which is generally 12 to 14-percent of its gross weight (GVWR).

Most hitches mounted on 5th wheels will NOT be rated for use with a weight distribution system. To use one of these systems, like the Equal-I-zer # EQ37100ET which includes built-in sway control, the hitch MUST be rated for such a use. The hitch sticker will tell you if it is rated for use with WD systems; it must explicitly state that it is. Simple friction bar sway control devices like # 83660 can't keep up with this kind of sway issue. If your 5th wheel's trailer hitch is rated for use with WD please tell me.

Your best remedy for the sway in your tandem towing setup is going to be very careful loading of the boat trailer to increase its tongue weight. Without enough TW the engine will act like a clock's pendulum that swings back and forth. Once this sway starts it will be very hard to stop it so it is best to try your best to avoid the sway through careful loading.

You need to be aware that as you increase the TW at the front of the boat trailer, that will push down more on the rear of the 5th wheel, reducing its pin weight at the truck. Some loading experiments and trial runs are really your best method to find the best compromise.

expert reply by: Adam R

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