SMI Stay-IN-Play Duo Brake system

SMI Stay-IN-Play Duo Brake system

Item # 9599006

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List Price: $1,099.95

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No more boxes! That is the cry of our customers. The Stay-IN-Play DUO answers the cry. Duo's small operating unit is installed under the hood so you never know it is there. No messy components scattered in the towed vehicle to complicate things; just a small operating module to control the towed vehicle brakes with no physical connection to the motorhome.


DUO combines the power of air pressure and the gentleness of vacuum to give you the fastest most powerful self contained supplemental brake ever. Duo uses the power and speed of air pressure to activate your towed vehicle brake pedal while creating vacuum for the power brake system. These two features combine to create the only progressive and proportionate vacuum assisted system with total control. Duo requires BOTH deceleration AND coach brake lights to apply the towed vehicle brakes. By combining two separate signals the need for complicated electronics is eliminated, which provides you a more reliable long lasting system. In addition, DUO is the pioneer in user friendly operation; "Just Turn it on...and Tow." This simple technology was first introduced in 2003. Tried and true, DUO does not have to be taken in and out for normal operation of the towed vehicle. Unhook the car and drive off, thats all. No box, no wires, in fact, no physical connection to the motorhome at all.


The Stay-IN-Play DUO system energizes the towed vehicle’s power brakes without the engine running, so you have a soft brake pedal. Once engaged, DUO replenishes the vacuum in the car's power brake system. By replenishing vacuum, gentle smooth pressure is applied to the towed vehicle’s brakes. With the power brakes active, only 10 - 12 pounds of pressure is required to provide a gentle smooth stop.


Activation of the towed vehicle's brakes require BOTH deceleration and the brake lights from the motorhome. Once BOTH signals are present, DUO gently applies the brakes. There is no complicated gain or sensitivity to achieve the proportionate balance of brake effort, it is all automatic. Automatically, once engaged, DUO will apply progressive brake effort in the towed vehicle. Because DUO uses both brake lights from the coach and deceleration, there is absolutely no delay. This becomes critical in a panic stop. Systems that use only deceleration must "think" first, is this a step grade, is this a large bump, or is this stopping? Time translates to feet while towing and in a panic stop, inches are important. No self contained system applies brakes faster than the DUO.


"Coach Notification" is another important aspect of any supplemental brake system. Some claim to have it, but really do not; while others do not really tell you about the position of the brake pedal in the towed vehicle. Without question, the most important information while towing is the status of the braking system in the towed vehicle. "Are the brakes applied?" That is the question. When researching brake systems, ask the question, "Do you have coach notification FROM THE TOWED VEHICLES BRAKE PEDAL SWITCH?" Many will claim to have a signal but do not, and others will have a signal from some other source. The only reliable and complete signal must originate from the towed-vehicle's brake switch. If the light is on, the brakes are on, period. What you do not want is a problem while you are towing. Knowing the position of the brake pedal gives you that peace of mind.


Simple on/off towing, the gentleness of vacuum, the speed and power of air pressure, dual signal activation, and reliable coach notification all combine to provide the most powerful easy to use system available today.


Installation instructions


Old part number





"...acts more like real brakes, it's the best!" - Jim Clarkson, Hitchsource First Customer For SMI Duo


Manufacturer: SMI Braking

7 reviews

Michael Burmer 05/01/2018

Great fit for my 16 Colorado Z71. Although more difficult to install than the portable units, now I donít need to deal with anything in order to hook up and go. Received from Hitchsource in a timely fashion and with a good price. I received prompt responses from DEMCO to my questions. I would caution others that although online videos are very helpful, the Colorado specific one I observed installed the check valve in the wrong location(between motor and vacuum pump). It is not between the motor and brake booster as required. There is room just on the passenger side of the booster if you remove the engine cover. I also installed a Roadmaster battery disconnect with a button hidden behind the parking brake, so no need to disconnect the... Read More

William Bulkley 03/28/2018

I have no mechanical abilities. Great youtube Video on installation for our Cad. SRX. Takes time but, was able to do install myself. HitchSource was a great help in deciding on preferred package to get out towed on the road.

Mark Boldenow 05/12/2017

A great brake system. A lot of work and wiring but doable if your handy.

Eddie Ray 08/28/2015

So we finished the install today. We had finished the Jeep install part a Month ago. All went smooth just slow on my part. Took our time and ran all wires in Convoluted Tubing. Install was pretty straight forward just followed the instruction.
I wanted the brake notification light on the dash of the MH. What I did was attached the light wire to the Jeep Brake switch and ran the wires to the 6 pin connector on the front of the Jeep. I used a quick connector for the ground and placed the Hot in the Center Hole of the 6 pin (was not being used) which is the accessory slot. I then cut the Center Wire on the MH 7 pin connector which is used for Trailer or Toad Backup Lights (was not used in my setup) and ran a single wire in Convoluted... Read More

Mike Lloyd 01/12/2012

Awesome product, easy install, fast shipping and great price and as always Hitchsource helpful courteous and friendly

Keith Shillington 10/18/2011

This is a great product. I installed it into my 1985 Jeep CJ7. Some of the mechanical mounting was a little challenging. I wound up installing the controller/switch box inside the glove box; the compressor unit onto the wheelwell just in front of the battery, above the starter solenoid - with a couple brackets to help stabilize it. I also needed to add an elbow into the vacuum line - the distance from the master cylinder to the intake manifold did not afford simply adding the tee and check valve in-line.
Although, I have only driven with it once so far; and feel that I need to make some more adjustments; but it certainly functions as advertised, and the installation CD; albeit designed for a modern Honda; gave pretty easily followable... Read More

Larry D Thomson 10/12/2011

Installation instructions and DVD were very good. As with any system, finding a way to thread the wires is often the greatest challenge. On my 2004 Jeep Liberty, I found a plug just below where the main wiring harness penetrates the firewall. After removing it with a screwdriver, the wires fed easily. After removing the plug, I drilled two holes (one for wires and one for the vacuum line) in the plug and threaded it onto the wires & line. That way, the plug went back in and made it easier to seal with silicon glue. First, test-drive went well. I hardly knew the car was behind me. SMI braking system worked flawlessly. I'm looking forward to many years of RVing. Finally, I'd like to thank the staff at HitchSource for recommending the SMI... Read More

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Installation Instructions

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