Turning / Cutting brake install

[Uzzirider]

After seeing the Trail Turn feature in action on the Bronco, we're trying hard to duplicate it on my 2018 F150. Would really help the turning radius, especially with aftermarket suspension and bigger tires. We've got the mechanical part installed, but need to work out the plumbing so it will cooperate with factory ABS & sensors.
Seems that a dual in, dual out turning brake could just be spliced between the brake booster and rear calipers. During normal braking, fluid would pass through the turning brake and allow normal brake function. But when you grab the hand brake, it would take over the line and activate the specific rear caliper. Anyone done this? Any thoughts or electronic pitfalls we're overlooking?

 

[Old-Raptor-guy]

Interesting, I have been looking at a way to do it with the electronic park brake on my 2020.

 

[Uzzirider]

This truck has the electronic parking brake too. It would be nice to use that, just seemed less intuitive. For example, can the E-brake be modulated? Or is it just lock / off?

 

[Old-Raptor-guy]

The ABS module engages the park brake and stops it when current flow reaches a set limit. It would take some sofisticated equipment to modulate the park brake.

If you watch the bronco it doesn't modulate it drags a tire.

I believe the Gen 3 raptor has trail turn also.

I also believe it is 100% software as all the hardware is there.

I am looking for use on tight trails

The issue I need to figure out is will the ABS module engage one park brake if the other is disconnected. I already know it makes the ABS module (and 8 other computers) very unhappy.

But if it was just for a moment while I made a tight turn that would be okay with me.

 

[Uzzirider]

But if it was just for a moment while I made a tight turn that would be okay with me.

Same here. How have you implemented this in your truck?

A hoon handle would be fun, but main functionality we're trying to accomplish is 'trail turn'. So locking a left or right parking brake would work. I'd imagine that with the correct supply voltage, and a diode on the OEM parking brake wires, you could wire switched secondary inputs to each electronic brake input. Then use the switches to lock up one caliper at a time?

 

[Old-Raptor-guy]

So, I haven't tried anything yet. Mostly theory at this point.

My idea is this, also remember I am not looking for high speed but when I am stuck in a tight spot.

Splice a switch into one wire on each park brake motor. Actuate the park brake and the flip a switch to the inside wheel to create an open circuit so the ABS can not release that wheel. Make the turn and switch the switch back to "ON"

I would tap into the harness under the hood to keep from running wires the length of the truck.

I have a couple experiments to try first.

 

[Uzzirider]

I have a couple experiments to try first.

Any updates with the electric parking brake idea?

 

[Uzzirider]

Splice a switch into one wire on each park brake motor. Actuate the park brake and the flip a switch to the inside wheel to create an open circuit so the ABS can not release that wheel. Make the turn and switch the switch back to "ON"

I measured voltage at the caliper. There are only two wires, and the system seems to operate with +12V down one wire when engaging the E-caliper, then reversing polarity and sending +12V down the other wire to release the E-caliper. I also noticed that if you unplug the caliper wires from the caliper, you get an error message, warning screen, etc.
So we could splice switches into the caliper lines, but it's likely to cause some temporary error messages.