Trailer Sway Control

[fudge_brownie]

My 2012 Sequoia and similar Tundra and Tacoma models come with TSC. The description of TSC states: "First it detects the trailer sway, often before the driver will. Then it automatically applies brake pressure to the individual trailer wheels."

What caught my eye was the statement about applying braking to individual wheels. I do not question that the vehicle can send a signal to say only use the drivers side brakes, my question is the trailer capable of interpreting such a signal and act accordingly? I doubt the trailer is capable of differentiating front to back wheels but what about driver versus curb side?

[cpaharley2008]

I'm not sure if the trailer brakes are activated with the tow vehicles sway control braking action? I would also be curious to know if the brake lights are activated to warn others of the braking or is the sway braking so minute that no other function is impacted?

[fudge_brownie]

Toyota states that when TSC is activated the brake lights automatically come on to warn drivers to the rear.

[rubicon327]

Originally Posted by fudge_brownie

My 2012 Sequoia and similar Tundra and Tacoma models come with TSC. The description of TSC states: "First it detects the trailer sway, often before the driver will. Then it automatically applies brake pressure to the individual trailer wheels."

What caught my eye was the statement about applying braking to individual wheels. I do not question that the vehicle can send a signal to say only use the drivers side brakes, my question is the trailer capable of interpreting such a signal and act accordingly? I doubt the trailer is capable of differentiating front to back wheels but what about driver versus curb side?

Paul: does it actually say "individual trailer wheels" or vehicle wheels? My understanding is the system leverages the onboard vehicle stability control (VSC) system which manipulates engine speed and brakes individual tow vehicle wheels to counteract sway. Even if there is a signal to the trailer as part of the system a normal 7 pin only has one output from the brake controller so there is no differentiation between brakes on the drivers or passenger side of the trailer.

On one of the Toyota forums a driver reported he had TSC and his trailer started to sway. His traction control light came on and the trailer sway subsided. It was a smaller trailer without brakes.

It appears it is for that sudden event (crosswind, quick manuever) that induces sway and is certainly not meant to be used as a substitute for proper trailer loading and mechanical sway control devices.

[cpaharley2008]

Yes I agree, it is an all or nothing for the trailer brakes to operate with only a 7 pin set up.

[Brian B-P]

Originally Posted by fudge_brownie

...
What caught my eye was the statement about applying braking to individual wheels. I do not question that the vehicle can send a signal to say only use the drivers side brakes, my question is the trailer capable of interpreting such a signal and act accordingly? I doubt the trailer is capable of differentiating front to back wheels but what about driver versus curb side?

There is no way for the tow vehicle to apply brakes to trailer wheels individually, or even just to one side or the other. All trailer brakes are connected in parallel to a single wire; the voltage on the wire simply determines the trailer brake force, with no intelligent signalling. The description given is incorrect... perhaps the result of a misunderstanding by a writer at Toyota.

Tow vehicle sway control systems can:

1. apply all trailer brakes together, and/or
2. apply tow vehicle brakes individually, as they do for stability control but recognizing that a trailer is attached so the correct action is a bit different.

This is the description from the 2016 Sequoia owner's manual (pg. 246):

Trailer Sway Control
Helps the driver to control trailer sway by selectively applying brake pressure for individual wheels and reducing engine torque when trailer sway is detected.

That's individual wheels of the Sequoia. Although there are many more references to TSC in the manual, I found no mention of applying trailer brakes at all. Apparently, they fixed the 2012 error.

There are trailer-mounted systems which do brake the left and right sides of the trailer separately, such as Dexter Sway Control.

Edit note: Dave (rubicon327) posted while I was composing my reply and covered most of this, but I already posted it, so I'll leave it...

[fudge_brownie]

Thank you for confirming what I thought. It did not seem possible to do individual wheels with what I knew of the wiring harness. I will admit it sounds like a neat idea.

[Dave Walter]

On a tow vehicle where the 4 wheels are relatively widely spaced, braking on individual wheels does have certain advantages in giving the vehicle greater control in poor stability situations (my FJ has individual wheel braking and it is relatively difficult to drift around a corner on ice as the computer takes over and brakes individual wheels to stop the drift. However, I cannot really imagine any advantage to having individual wheel braking capabilities on an Escape trailer, whether it is single axle or tandem. In a sway situation, you want to apply the brakes on all of the trailer wheels at once to slow down the trailer and stop the sway. Applying brakes on a single trailer wheel would have little benefit to maintaining stability.

[Kountrykamper]

Trailer Sway Control
Helps the driver to control trailer sway by selectively applying brake pressure for individual wheels and reducing engine torque when trailer sway is detected.


My Tundra says the same thing.

[Brian B-P]

Originally Posted by Kountrykamper

Trailer Sway Control
Helps the driver to control trailer sway by selectively applying brake pressure for individual wheels and reducing engine torque when trailer sway is detected.


My Tundra says the same thing.

This is the same as the 2016 Sequoia, but does not have the (incorrect) reference to braking trailer wheels that Paul quoted for 2012.

[Brian B-P]

While I don't see any reason to separately apply the leading and trailing axle brakes, the left and right trailer wheels are widely separated (even wider than the tug) and so applying them separately applies substantial torque to rotate the trailer about the vertical axis. Since sway is unwanted rotation about the vertical axis, appropriately timed application of trailer brakes on only one side would be very effective in damping sway, just as applying tow vehicle brakes on only one side controls rotation.

Just continuously dragging one trailer brake would be useless, but neither motor vehicle nor trailer sway control systems work that way.

Of course, any trailer braking at all also helps, and installation is easier if stock trailer wiring can be left as-is, so the most common approach among brake-based trailer sway control systems is just to apply all trailer brakes together. They are generally located entirely on the trailer, avoiding the challenge of interacting with a variety of tow vehicles.

Here are the brake-based trailer sway control systems that I am aware of:

• Separate application:
  • Dexter Sway Control
  • Tuscon (DirectLink) Sway Control TSC-1000
• Simultaneous application:
  • Hayes Sway Master (plugs into wiring inline with connector, so has no access to separate left and right wiring)
  • AL-KO ESC (does not interrupt stock brake wiring so cannot control sides separately)
  • AL-KO ATC (for European mechanical brakes)
  • Lippert Sway Command

Heavy commercial trucks have had anti-lock braking systems (ABS) which individually control the brakes at each wheel, but I don't know if any trailer stability control systems for these trucks have made it into production.