Does Trailer Stability Control interfere with anti-sway control?

Trailer sway is a big problem when towing and particuarly today when we have ever-larger caravans with relatively small, over-rated tow vehicles. So, there’s a number of ways to mitigate sway and one is to fit a mechanical anti-sway system. That’s basically a device which stiffens the connection between towcar and trailer so the trailer can’t move as easily.

There’s also Trailer Stability Control (TSC) which is built into every modern towcar; it detects when trailer sway is happening, and brakes indvidual wheels on the towcar to quell the sway.

But what happens if you run such an anti-sway system and have electronic Trailer Stability Control on your towcar?

Here’s what reader Pam found:

“I have never towed my trailer since that first day with the truck sway control on. The first day when I was uncontrollably all over the road (over 50mph) I stopped & made adjustments to the trailer sway control & weight distribution bars every 30 mins or so. I had them in every possible configuration & nothing changed. It literally took me 12 hours to get 200 miles. With the truck sway control off towing has been something I can do. If towing was gonna be like it was that first day on the freeway, I would have sold my truck & trailer.”

So what’s going on? Given the TSC only activates if there’s sway, why is it causing problems?

My guess; the car TSC systems expects the trailer to put certain forces on the car at certain times. For example cornering, when the car knows how fast it is going and how quickly it is turning – that’s the yaw rate.

The anti sway control makes the trailer respond differently. The TSC system interprets this as sway and yaws the car to correct by applying brakes only to the left or right wheels. But the rig is not actually swaying…so the TSC’s “corrective” action induces sway! If you removed the anti sway I bet TSC would behave.

I have found a similar behaviour on racetracks with cars at speed when I make a tiny skid correction and so does poorly-calibrated ESC and the two combined actually make it worse in the opposition direction.

But reader Tyler wrote this:

“I have a ReCurve R3 on my 2021 Jayco 24BH. My 2011 Ford Expedition is what I tow it with and I had the Tuson TSC-1000 I installed on the trailer. My brake control is a Curt Spectrum. I also added SumoSprings to the coils on my rear on the Expedition. Interestingly enough those little foam SumoSprings did more to smoothen out the ride and reduce porpoising than all the other components. Go figure. So far I have not experienced any problems with any part of the system. I can highly recommend reaching out to Tuson as they did extensive testing with their system at proving grounds, and even forced the TSC to battle with their sway control module with no ill effects. From what I recall the Tuson system responds faster than the TSC in the vehicle, and even if the sway event was extreme enough to kick the TSC on in the vehicle they were complimentary to each other in bringing the trailer under control. Same thing with Mechanical Sway control. It was all complimentary with Tyson’s testing.”

So, it all depends…keen to hear from other people who run anti-sway systems. However, my view is that a good trailer setup is stable without any anti-sway or weight-distribution system.

Here’s an explanation of how trailer brakes can combat sway: