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Demco SBS Stay-IN-Play DUO Supplemental Braking System - Proportional

Demco SBS Stay-IN-Play DUO Supplemental Braking System - Proportional

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Tow Bar Braking Systems

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Demco SBS Stay-IN-Play DUO Supplemental Braking System - Proportional Power Assist Brake Compatible SM99251
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In Use/Installed

Customer Photos

Product Expert Mike S

Is this right for you? Product Expert Mike S says:

Yes, if you:

  • Don’t have time to waste setting up a portable system before every trip
  • Don’t have extra storage space in your RV to store a portable box system
  • Want a permanent system that’s easy to install

No, if you:

  • Upgrade your towed car every few years
Get automatic, proportional braking with a system that never has to be removed, replaced, or reset. The DUO activates when your RV's brake lights go on and an inertia sensor in the towed car detects deceleration. No false braking. Lowest Prices for the best tow bar braking systems from Demco. Demco SBS Stay-IN-Play DUO Supplemental Braking System - Proportional part number SM99251 can be ordered online at etrailer.com or call 800-298-1624 for expert service.
  • All Info
  • Reviews (150)
  • Q & A (1577)
  • Photos
  • Why etrailer?

Demco Tow Bar Braking Systems

  • Demco
  • Brake Systems
  • Hydraulic Brakes
  • Proportional System
  • Fixed System
  • One Time Set-Up
  • Power Assist Brake Compatible

Get automatic, proportional braking with a system that never has to be removed, replaced, or reset. The DUO activates when your RV's brake lights go on and an inertia sensor in the towed car detects deceleration. No false braking.


  • Supplemental braking system applies towed vehicle's brakes in proportion to braking action of RV
    • Towed car's brakes are activated at the same time and with the same intensity as those in your motor home
  • Inertia sensor detects deceleration and signals system to activate brake pedal with proportionate amount of pressure
  • No false braking
    • Coach brake light must be on for system to activate towed car's brakes
  • Sensitivity control on the inertia sensor lets you regulate how aggressively the towed car's brakes activate
  • One-time setup - no need to remove or to activate each time you tow
    • Operating unit and actuating cylinder stay hidden so everything is out of your way when driving
    • Inertia sensor mounts in the cab of the vehicle
    • System automatically functions when towed vehicle is hitched to RV
  • LED coach notification system illuminates when the towed vehicle's brakes are applied
    • Connects to towed car's brake light switch to ensure proper reading
  • Vacuum pump restores towed car's vacuum after each braking event
    • Less force is needed to move the brake pedal in the car, resulting in more natural braking and less risk of damage
    • Compatible with vehicles that have continuous-power-assist brakes
  • Breakaway included
  • Necessary installation components and instructions included
  • Made in the USA


  • Operating unit dimensions: 8" long x 5" wide x 2-1/4" tall
  • 5-Year warranty

Note: Works with Re-Install Kit SM6270 to use in another tow vehicle.

A supplemental braking system is a must when towing a car or truck behind your RV. Without it, the weight of the towed car can create a safety hazard, strain your RV's brakes, or affect your RV's warranty. Most states require a supplemental braking system.

Automatic, Proportional Braking

There are many supplemental braking systems available to RV owners who choose to tow a car. Stay-IN-Play DUO combines the best features into a single system that is both automatic and fully proportional. This system relies not only on your towed car's momentum to activate, but also on your RV's brake light signal. As a result, the DUO will automatically activate any time you engage your RV's brakes, so long as there is enough deceleration for the system to detect. And when it does activate, your towed car's brakes will engage with an intensity that matches the slowing or stopping action of your RV.

An inertia-sensing mercury switch inside the DUO's controller is what makes this system proportional. This switch reads and interprets changes in forward momentum that occur when your towing setup decelerates. As your RV and car slow down, this switch sends a signal to activate your towed vehicle's brake pedal with an intensity that matches the deceleration of your RV. The result is even braking across your towing setup. Whether you lightly tap the brakes in your RV or apply them hard in a panic situation, your towed car's brakes will be applied proportionately.

Dual Activation Signals

G Force Controller

The G-Force controller is responsible for sending the signal that activates the brakes in your towed car. When the coach brake lights come on, the tow bar wiring sends a signal to this controller. This signal powers the internal, inertia-sensing mercury switch, enabling it to detect deceleration. If a change in forward momentum is detected, the G-Force controller initiates the braking process by sending an activation signal to the system's operating unit.

If the mercury switch is powered but there is no change in momentum, the system will not activate the towed car's brakes. Likewise, if a decrease in forward momentum occurs but there is no brake light signal from the RV, the inertia sensor will not be able to register the deceleration, and the system will not activate the towed car's brakes.

Because the DUO will not work without your RV brakes being applied, there is no false braking. When you downshift in your RV without applying the brakes, the DUO will not mistakenly depress your towed car's brake pedal because that first activation signal is not there. And because there is no time delay, this proportional system delivers instant braking in an emergency.

Note: The G-Force controller mounts in the towed car and must be pointed it in the direction of travel - with the toggle switch facing the rear of your vehicle - for the internal sensor to function properly.

Sensitivity Adjustment

You can adjust the sensitivity of the inertia-sensing mercury switch with a knob on the front of the G-Force controller. Adjusting the sensitivity lets you decide how intense the change in momentum must be for the sensor to respond. Adjust it to fit your personal preference so that you can get a customized braking experience. Set the sensitivity low and the DUO will only respond when you forcibly step on your RV's brake pedal. Set the sensitivity high and it will respond when you merely tap your RV's brakes.

To fine-tune the sensitivity, first move the knob all the way to its most sensitive setting. From there, you can apply the coach brakes and gradually move the knob until you get the setting right where you want it. You only need to set the sensitivity upon initial setup.

Permanent Installation with Concealed Components

Operating Unit

The operating unit receives the signal from the G-Force controller to activate. It then delivers air through a hose to the actuating cylinder, which depresses the towed car's brake pedal with a pressure that ensures your car will brake in proportion to the deceleration of your RV.

DUO Under Hood

Once you install the Stay-IN-Play DUO's operating unit under the hood of your towed vehicle, it stays concealed. Not only will it be installed and ready for the next time you want to tow your car, but it will also be out of the way so that you won't notice it when you drive your car normally. In addition, there is no need to constantly set up or remove this system. As a result, you don't need to worry about where to store the components when you're not towing.

Actuating Cylinder

Small Cylinder

The actuating cylinder depresses your towed car's brake pedal upon receiving air from the operating unit. This small cylinder stays mounted on the arm of your towed car's brake pedal at all times and will not interfere with braking while driving.

Actuator on Pedal

Mount this cylinder so that it is perpendicular to the firewall when you depress the brake pedal. A clamp anchors the actuator to the firewall.

To connect the actuating cylinder to the operating unit, you will need to run the included air hose through your towed car's firewall. You can usually create the necessary, small opening without drilling. In most instances, you can cut a slit in the hood release cable grommet. Simply cut the end of the air line at an angle to poke it through the slit.

Vacuum Pressure Creates Smooth Braking

Normally, when you activate the brakes in your vehicle, a vacuum multiplies the pressure you apply to your brake pedal, creating the force necessary to stop the full weight of the moving car. On most cars and trucks, this vacuum-assist function does not work when the engine is off. As a result, many supplemental braking systems on the market have to use an excessive amount of pressure to effectively depress the towed car's brake pedal.

The Stay-IN-Play DUO's operating unit ties into your car's vacuum line and uses a built-in vacuum pump to activate the vacuum-assist function of your car's brakes when it's being towed. As a result, the actuating cylinder of the Stay-IN-Play DUO does not need to apply extreme force to the brake pedal to achieve proper braking. The Stay-IN-Play DUO will replenish your towed car's vacuum after each braking event so that you will get smooth, even braking every time.

Built-In Safety Features

Most supplemental braking systems have methods of letting you know you when the system itself is activated, regardless of whether the towed car's brake pedal is depressed. Such setups leave opportunities for false notification. The Stay-IN-Play DUO's system is different. This system's LED monitor connects to your towed car's brake light switch. When your car's brake light goes on or off, so does the notification light. So you can tell whether your car's brake pedal is depressed.

You can install the monitor light on your RV's dash, or you can save time by attaching the monitor light to the back of the rearview mirror of the towed vehicle. This way you can see the light from your RV's backup camera or rearview mirror. The system includes the necessary parts for either installation method.

The breakaway system ensures that your car will come safely to a stop if it accidentally detaches from the RV while you are towing. A switch mounts to the front of the towed vehicle. This switch - which is wired into the operating unit - includes a pin that connects to your RV's hitch receiver with a breakaway cable. If the car separates, the cable pulls the pin from the switch, causing a signal to be sent to the operating unit.

9599006 Demco SBS - (Formerly SMI) Stay-IN-Play DUO Supplemental Proportional Braking System

Replaces Demco SBS SM99251

Item # SM99251

Installation Details SM99251 Installation instructions

This Product Fits The Following Vehicles

Customer Reviews

Demco SBS Stay-IN-Play DUO Supplemental Braking System - Proportional - SM99251

Average Customer Rating:  4.8 out of 5 stars   (150 Customer Reviews)

Get automatic, proportional braking with a system that never has to be removed, replaced, or reset. The DUO activates when your RV's brake lights go on and an inertia sensor in the towed car detects deceleration. No false braking.

- SM99251

Haven't actually had the chance to tow behind yet so this is just for the install. It took me quite a long time to install but, that's not the products fault. Everything you need to do the job is included. I only give it 4 stars because the system uses the towed vehicles battery to activate the vacuum/compressor pump, so it would be possible to run the battery down as there is no charge circuit from the towing vehicle. I did choose to add one though. Other than that I'm sure it'll work fine. It was installed on a 1983 Vanagon.

- SM99251
2005 Jeep Liberty

I'm very pleased with this Stay-in-Play /DUO Braking System which I installed on my 2005 Jeep Liberty. I debated wheather I dared install it myself, but with the video instructions I decided that I could. I watched the video a couple of times, then followed it step by step during the installation, and it went pretty smoothly. One issue I had is that they changed the instalation of the LED indecator light, since the making of the video, so the parts did not come as described on the video. I do prefer the new method, as described in the installation manual, but it does require a toggle switch to turn it off. I installed one just below the Control Unit inside the car (see photo). I was also very impressed since, right after ordering the system, I found it for less on another web site. I emailed eTrailer about my disappointing discovery, and they credited me back the difference. GREAT COMPANY!

One year later, the system is still working great. Still very pleased.
Robert P - 12/09/2019

- SM99251

I have not actually tried it on the road, but it activates as advertised. Thus only 4 stars. It replaced an old Cumbersome Brake Buddy. Working under the dash was the most difficult part. The LED notification lite does not work the wire is very flimsy. Will update when I get on the road.

- SM99251

Very happy with the way this turned out. Video was very helpful. Only thing I didn't really care for was the red LED that was to be mounted on mirror. Purchased a red LED light at parts store and mounted in grill, see picture, using alternate connection. Much easier to connect and much easier to see in RV camera.

- SM99251

Package arrived quickly. Haven't installed yet, so no opinion on how well it works. REALLY wish it had the wired light for the RV dash confirming when the brakes are applied (like invisibrake has). Don't want to have to look in the rear view camera to see the light on the tow car's mirror. You can purchase a wifi light for the RV that works with this, but that's more cost and not nearly as convenient.

- SM99251

After 7,000 miles towing manual tranny Honda Fit, it works great with no problems. Extremely easy to use, just connect cables to MH and flip on power switch in car. Nothing else to do. I installed this myself using the etrailer installation video, which was excellent and easy to follow. Highly recommend.

- SM99251

The install was not easy. You need to follow the instructions in the videos. The product works very well and I would recommend it to anyone in need of a very good braking system.

- SM99251

I am very happy with the Demco Stay-In-Play. The etrailer instalation video were a great help and an easy install for the DIY. It works as advertized and fits under the drivers seat on a JL Jeep Wrangler. It was a good purchase.

- SM99251

As a result of changing motorhomes, we had to switch from an Air Force One breaking unit to a Stay ñ Play Duo. Thanks to the video provided? by etrailer.com, the change over was VERY EASY. We really like how the new system works. Setup is so straight forward. Thanks etrailer for all your support.

The Stay n Play Duo has been working great. Unfortunately, due to the current situation with COVID 19, we have not gotten the opportunity to use it this year. We have recently purchased a new Jeep and have purchased the same braking system for it as well.
Gary C - 05/09/2020

- SM99251
2016 Ford Edge

Thanks to installation videos provided by etrailer, I felt confident that I could do the install myself. I had never pulled off moldings and panels in a car before, but with your videos as guidance , it was a breeze. This system was going into a 2016 Ford Edge 3.5L AWD and your (and SMI's) instructions call for installation of 2 check valves. After calling SMI to clarify the install points, it got even easier, as only one valve is required, and is ridiculously simple to install it. No cutting of original car hoses required (see photo). After everything was installed, the whole setup just simply worked, no troubleshooting required. That was fun and it is totally doable, even for the average guy like myself.

The rear-view camera display in my RV is not good enough to show the operation of the brake notification LED which is applied to the rear-view mirror in the towed car. I installed a small light in the RV dash and ran wiring all the way back to the toad, with a disconnect plug at the hitch, of course. Now it is easy to see when the car brakes come on. Else, the system works great.
Herbert M - 07/13/2018

- SM99251
2003 Subaru Outback Wagon

I chose to go with this unit because I didn't like the idea of the other types that mash the brake pedal without any vacuum assist & the fact that you have to remove, then reinstall them each time you want to use the car. This ended up TOUGH install. Not because of the unit, but rather the lack of ANY room under the hood on my 2003 Subaru Outback Wagon to mount the operating unit. The only place I could find that would be out of the way was under the driver's seat of all places! Luckily there was JUST enough hose with the unit to reach all the way to the brake booster. I had to cut the carpeting so the seat would clear the operating unit during movement without any chance of contact. There was no hole in the firewall large enough to accommodate the hose so I had to drill a hole for that although I was able to route the wiring through a small rubber grommet. Routing the hose to the firewall was a real challenge! I ended up running it through the heater duct under the driver's floor mat to the left side kick panel, then up over the pedals keeping clear of any moving parts. WHEW!! The brake pedal actuator went on without much fuss, although with my large feet I have noticed I'll catch the actuator with my toe on occasion. I may mark the location it's in now & merely raise it up a tab in between trips. The wiring was pretty much straight forward, there was plenty of included wire & I had JUST enough room tho mount the G-Force Controller on the left kick panel covering without interfering with my feet. The breakaway switch I fastened to the body in front & below the radiator. I read where everyone was saying you need to have a battery cut-off device to keep the braking system from draining the battery over time, but I had power from the RV keeping the battery fresh so I didn't worry about that & saved myself the $180 for the cost of an automatic battery disconnect. After installation, I sat in the car while we towed it around the neighborhood to see how it worked & made the necessary adjustments to the G-Force Controller. Now THAT was weird! What with the car steering itself & braking too. We just got back from a 4,000+ mile trip & everything worked fine. On occasion I forgot to flip the switch to turn the system off, but it didn't seem to make much of a difference. All in all a great system!

- SM99251
2000 Jeep Wrangler

All I can comment on so far is etrailers fast delivery I ordered it on Wednesday and had it on Friday with regular free shipping. I am going to install the Stay-In-Play brake system on my 2000 Jeep Wrangler next week and the taking it on a trip across South Dakota Wyoming Montana and back to Nebraska. I will give the brake controller a good test and let you know what I think when I get back. So far etrailer gets 5 stars for their response.

- SM99251

Great product. Some difficulty in installing, but worked extremely well. Had an issue with a wire coming undone and didn't have brakes for part of a trip, but re-wired and continues to work well. To me, the best one on the market.

GREAT product! Works outstanding. I especially like the LED indicator on the back of the rearview mirror that shows it is engaged!
Ron B - 08/03/2020

- SM99251
2018 Jeep Wrangler

After doing much research and reading many reviews and watching a lot of your instructional videos I chose the Stay-in-Play Duo. It came complete with instructions and extra parts for any application. I like the fact that after everything is installed it is just a matter of flipping a switch and checking it out and drive off. I mounted it in a 2018 Jeep wrangler, not very much room for the operating unit, but I I went off of one of your videos on a 2017 Jeep Wrangler Unlimited and mounted it underneath above the cross frame below and behind the radiator but still protected from the elements. Not a lot of room under the dash either, but everything is in and looks great and ready for the 1st trip.

- SM99251

It wasn't easy to get everything installed in a way that looked neat and professional but in the end the ease with which you can hook up the car and start towing makes it worth it. I bought a replacement factory vacuum pump line so that I didn't have to worry about ruining the original one and as a result the installation looks that much better. Literally all I have to do is flip a switch once the car is connected and I'm ready to go. Given a second opportunity to do the installation I would mount the LED light strip vertically on the backside of the rear view mirror to make it a bit more visible but other than that, I'm happy with how it turned out and the system works great.

- SM99251
2012 Dodge Charger

I installed this in a 2012 mini Cooper S. With the turbo charger there is no room in the engine compartment for the system unit, so I mounted it under the passenger seat. I had to remove the seat, cut out the carpet, mount the unit, and then buy longer seat attachment bolts. I used half inch thick spacers between the seat track in the floorboard. Made a long run for the vacuum hose to get up to the engine compartment through the firewall. By removing the cowling on the driver side, it exposes a huge Gromit where the main wiring harness passes through the firewall. It actually had two nipples ready to be cut off to run the vacuum hose and the wires through — so that part was pretty easy. I haven’t towed it behind the motorhome yet, but it passed all the start up tests the first time!

- SM99251

Can’t review the brake system yet as it will take some installing. But etrailer continues to amaze. Product arrived less than 24 hours after ordering and appears to be undamaged. The product information available online is amazing and made my selection simple.

etrailer shipping was great - as it usually is. Installation on my Jeep Wrangler was straightforward and the provided instructions were outstanding. He system works great and I REALLY like that it’s always onboard and ready to go with the flip of a switch. I am 100 satisfied with this product.
Pete A - 03/16/2020

- SM99251
2015 Jeep Wrangler

SMI Stay in Play Duo installation in 2015 Jeep Wrangler Unlimited – Packaging was great with everything needed included plus extra items for various installation methods of you’re choosing. Upon initial investigation and survey, everything except the CD Information pack was accounted for. No big deal, as I had previously watched 2 different Youtube installations found on the internet. In fact, the internet videos were what I used as my step by step installation process, and the written instructions were only used for concerns where the video may not have been as clear as I had hoped for. Understanding that everyone has their own style and methods for doing this project, I purposely was not in a hurry to rush through it. All in all, I took @ 8 hours to install the Adapter 4 to 6 pole #30637, the EZMount Tow lights Kit, and the Stay in Play Duo Braking System. I choose the EZMount because I didn’t want to mess around with the OEM taillights and wiring. Magnetic lights don’t work so well on composite tops and I didn’t want to stick them to the sides of te Jeep, so I modified the EZ mount to wrap around the thickness of the rear glass hatch on both sides. I added a 2”x 4” pc of Velcro on the inside of the glass hatch and the mating surface of the plastic light housing - to hold the lamps in place until the rear gate was closed. I ran the wire harness on the inside under the trim all the way up to the front and through the grommet in the firewall. The flat 4 wire was routed and secured up to the Adapter 4 pole to 6 pole that I had fastened to the Blue Ox base plate. The actual installation of the SMI unit and assorted parts went rather smoothly. Most difficult issue was the lack of working space in front of the driver’s seat area. Installing the screw that holds the G force controller on the front (the side towards the front of the car) was difficult as it was almost a blind installation due to lack of room. The nut and fender washer used through the fire wall for attaching the air cylinder cable bracket was a challenge to reach - tight fit with not much room for one's hand and arm. Other than that, no big surprises – just a lot of tedious steps to do when you want to be sure that it is being installed properly – take your time and don’t be in a hurry. Once everything was installed – it all worked when I checked the system out. The only thing that may seem a bit odd is that when setting the G force initially, the compressor will shut off while adjusting per instructions. To do this initial adjustment, the wife stepped on the brake in the Motorhome, with the switch “On”. The compressor starts, and the brake is pushed down by the Air Cylinder, at which time I slowly adjusted the G force until the compressor shuts off. I secured the adjusting bolt and I told the wife to take her foot off the brake and then re-apply them. The compressor did not start again and the air cylinder did not apply the brakes in the Jeep. After setting the G force per instructions, the unit didn't turn on when the brakes in the Motorhome were applied - but since we were not moving - all I can assume is that the brake system will function while slowing down once the accelerometer setting (the sensitivity setting on the G force box) has been met. I assume that the sensitivity setting method includes a way to ensure the Jeep brakes are not engaged too frequently and only until needed. This is the only step that is a tad bit confusing without an explanation as to what to expect once the G force sensitivity is set. Lastly, I checked the brake away switch and it turned the compressor on and applied the brakes as expected. Overall - the installation went rather smoothly. Can't wait to see how the product works once we hit the road. I'll check back and provide an update later.

Still working as expected, trouble free and no problems since the install.
Mike A - 10/23/2018

- SM99251

I selected this item as an alternative to braking systems that sit in front of the driver seat and must be put in and taken out each time it is used. I like the fact that it is nearly undetectable once installed and works seamlessly. On installation the most difficult part was drilling the holes to screw the unit under the driver seat. The carpet being the primary problem in my experience, as it bound up around the drill bit.

- SM99251

Have this on a Jeep rubicon that gets abused and have had no issues with the braking system. Very happy and set up for towing is a breeze. Would buy again!

- SM99251
Chevrolet Equinox

I was looking for a good product that would be a easy to install and use when I purchased this for a new Equinox to tow behind the motor home. The finished look is well concealed as it should be and easy to operate when used. The instructions were fairly straightforward but has room for improvement in some critical areas of the install that could have turned out very bad such as where to go through the firewall and separate directions and photos for each option. One mistake I found not mentioned but should be is connecting the brake trigger wire to the third brake light of the motor home direct to avoid the turn signal mess.

- SM99251

Everything installed without any issues. I'm very particular so it took 2 days to complete everything. I'm sure a pro could do it much faster. Have towed the 4" lifted (and loaded) Jeep accross the Rockies about 6 times and everything is working perfectly!! Very happy camper!!

- SM99251

Sold and installed by etrailer. This brake setup is installed on our Jeep Wrangler and has worked well for us. We do occasionally hear the brake unit making a pulsating noise but it doesnt seem to effect the operation so we have never worried about it. The installation work is particularly neat and tidy. Thanks etrailer!

- SM99251

The supplemental brake system works as described. I rate it excellent because I would buy it again should I change tows. One simple turn of a switch turns it on without the hassle of an in and out box that you must stow somewhere between trips.

- SM99251

So glad we decided on this system. Lots of info and other ways to do this, but this is very simple to install, and super easy to use! Makes hook up a breeze, and easy to verify the function.

Show More Reviews

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  • Supplemental Breaking System and Lighting Kit to Flat Tow 2013 Honda Fit
    For lighting you can use the diode kit, # RM-15267, and not have to worry about cutting into the taillight housing. This will splice into your taillight wiring to allow your tow vehicle to control the taillight assemblies of the towed vehicle. This comes with a round 6-way connector that you will install on the front of your towed vehicle and enough coiled wire to go from there to the RV. The SMI DUO part # SM99251 you are thinking about is the way to go. This is our installers favorite...
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  • Parts Needed to Flat Tow 2018 Buick Envision
    I took a look at the online version of the owner's manual for your 2018 Buick Envision AWD and found that it can be flat towed behind an RV with all 4 wheels on the ground. I do recommend verifying this information in your copy of the manual as well as reviewing the specific steps you will need to take before pulling the vehicle. This section is titled "Recreational Vehicle Towing" in the manual. In order to flat tow your Buick Envision you will need a base plate kit, tow bar, safety...
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  • Are Additional Diodes Needed for Demco SBS Stay-IN-Play DUO Supplemental Braking System
    You will not need additional diodes when installing the Demco SBS Stay-IN-Play DUO Supplemental Braking System # SM99251. The 10 amp diode that come with the kit are only needed if your tow wiring harness is not diode-protected. Since yours is not, you will install the diodes in-line with the green and yellow wire from the G-Force controller to the green and yellow tow bar wires. I have added an install video for you to check out as well of the Demco SBS Stay-IN-Play DUO Supplemental...
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  • Tow Bar and Flat Tow Parts Needed for Heavy 2020 Ram 3500
    We can definitely get you a flat tow set up for your 2020 Ram 3500. These trucks are heavy, but the GVWR you are referring to is the gross weight, which is the max weight it can be when loaded with passengers and cargo. According to my research, a 2020 Ram 3500 has a curb weight (unloaded) of up to just over 7,500 lbs max. So even if you have some cargo in the truck, it is difficult to imagine you will be exceeding the 10,500 lb tow bar option you can use with a 2 inch hitch on your...
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  • Is Brake Light Relay Needed when Installing Tow Bar Lighting on 2019 Buick Envision
    When we installed the diode tow bar lighting kit part # RM-15267 on a 2019 Buick Envision we did not use a brake lite relay. If you wanted to watch our entire install of this kit on your vehicle to use as a guide check out the install video link I attached to this page.
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  • Will Stay-IN-Play Duo Supplemental Braking System Work on RV With Air Brakes
    Technically the SMI Stay-IN-Play DUO Supplemental Braking System # SM99251 you currently have is still going to "work" with your 2018 Jeep JL Wrangler Unlimited and new RV with air brakes, but the issue is that you are going to get false braking because it uses both the RV's brake lights and deceleration to apply the brakes. This is going to make your drive less comfortable and more importantly, wear out your Jeep's brakes quicker than need be. It could even go as far to drag the Jeep as...
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  • Recommended Supplemental Braking System to Flat Tow a 2019 Fiat 500
    The supplemental braking system I recommend for a 2019 Fiat 500 is the Stay-IN-Play DUO Supplemental Braking System part # SM99251 if the coach has hydraulic brakes or the Air Force One Supplemental Braking System part # SM99243 if the coach has air brakes. The Stay-IN-Play and Air Force One are two of my favorites because they are generally easier to install than most other permanent options. If you will not be installing the system yourself then the easier install means you could potentially...
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  • Mounting Location for Stay and Play DUO Operating Unit
    When I installed the Stay-IN-Play DUO # SM99251 in a 2018 Jeep Grand Cherokee I mounted the operating unit in the front of the engine bay on the core support. You can mount the operating unit anywhere that the wires and hoses can reach; it's just recommended that it mounts in the engine bay away from direct water exposure and extreme heat sources. After installing many flat tow set ups on different vehicles, the biggest piece of advice I can give you is to plan out your install. Take...
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  • Installing SMI Stay-in-Play DUO Braking System SM99251 in 2018 Jeep Wrangler JL
    My contact at SMI advised that the Stay-in-Play DUO Supplemental Braking System # SM99251 that you currently have installed in your 2006 Jeep TJ can be installed in the 2018 Jeep JL Wrangler by cutting the JL's 8mm hard plastic line and installing the SMI 3/8-inch vacuum hose. SMI recommends also using a worm clamp for a secure connection.
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  • Motorhome Mounted Monitor Light for Towed Vehicle Brakes
    The SMI Stay-IN-Play DUO Supplemental Braking System part # SM99251 comes with a monitor light that will get installed in the windshield of the tow vehicle and will then illuminate when the brakes in the towed vehicle are applied. If you want something in your motorhome that lets you know when the brakes in the towed vehicle are applied you can use the Roadmaster Universal Brake Monitor part # RM-9530.
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  • How to Install Stay-IN-Play DUO in New Jeep
    I spoke with my contact at SMI and he advised not to install the Stay-IN-Play DUO # SM99251, which you referenced, under the seat but to install it on the toe kick per the installation instructions. He said it will not work if placed under the seat because the unit needs to be mounted level as it is working off inertia. The operating unit measures 8" long x 6-1/4" x 2-1/2" tall. (See photo.) He said the units have been fitted in all new Jeep models and that they will fit, you will...
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  • Installing SMI Supplemental Braking System on 2015 Jeep Wrangler with Mopar Harness
    For your 2015 Jeep Wrangler I recommend going with either the SMI Air Force One Supplemental Braking System # SM99243 if your RV has air brakes or the SMI Stay-IN-Play DUO # SM99251 if it has hydraulic brakes. If you tow the Jeep somewhat often going with a permanent system like either of these options is a great idea. As for what you will need to do with regards to your existing OEM harness it depends a bit on which of the two above mentioned systems you need. With the Air Force...
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  • Parts Needed to Flat Tow 2005-2007 Jeep Liberty Behind RV
    In order to flat tow your Jeep Liberty behind an RV/motorhome, you need a base plate kit, a tow bar, safety cables, a lighting solution, a supplemental braking system, and likely a high-low adapter. Starting with the base plate kit, I recommend the Roadmaster EZ5 Base Plate Kit # RM-521423-5. These base plates are custom fit for your Jeep and feature a hidden bracket design for a clean look when you aren't towing. Its black powder coat finish is durable and will work do a nice job of...
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  • Is a Battery Charger Needed with the Stay-in Play Duo Supplemental Braking System?
    On your 2018 Jeep Wrangler, I am thrilled with the parts you ordered. The Mighty Cord Trailer Connector Adapter - 4-Way Flat to 6-Way Round - 12" Harness # A10-6034VP will give you the 12V charge line from your 7-way on your motorhome to give a maintenance charge to your Jeep battery. Although a charge line isn't required, the SMI Stay-IN-Play DUO Supplemental Braking System # SM99251 does use that vehicle battery, so I do recommend connecting it. You can simply connect the 12V wire...
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  • Recommendation Between Stay-IN-Play DUO, Air Force One, or Roadmaster Invisibrake for Tiffen Diesel
    Since your Tiffin diesel has air brakes I recommend going with the Air Force One, part # SM99243. Both of the other systems use the brake lights to engage the brakes on your 2016 Jeep Cherokee. Since the coach's exhaust brakes does light the brake lights up this can cause false braking when you don't want it. The Air Force One, however, does not engage the Jeep's brakes from the brake lights, so there won't be any false braking when using it. The Air Force One is more of an installation...
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  • Compatibility of Braking System and Battery Disconnect When Towing 2019 GMC Sierra 1500 Limited
    Yes. The SMI Stay-IN-Play DUO Supplemental Braking System - Proportional # SM99251 will be functional even with the Roadmaster Automatic Battery Disconnect with Switch for Towed Vehicle w/ Supplemental Braking System # RM-766 in place on your 2019 GMC Sierra 1500 Limited. I recommend using the Roadmaster Battery Charge Line Kit for Towed Vehicles # RM-156-25 along with the Roadmaster Diode 7-Wire to 6-Wire Flexo-Coil Wiring Kit # RM-15267 to allow you to charge the battery on your truck...
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  • Troubleshooting 2014 Jeep Wrangler Brakes Pulsing With Motorhome Turn Signals
    From what you described it sounds like you need to install the Roadmaster Brake-Lite Relay Kit # RM-88400. If your towed vehicle is the 2014 Jeep Wrangler that you input for your vehicle information then this makes sense. Typically we recommend disconnecting the battery when flat towing this vehicle. If you were to disconnect the battery then your SMI Stay-IN-Play DUO # SM99251 wouldn't cause the brakes to pulse when your blinker is used on your motorhome. When I spoke with my contact...
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  • Does SMI DUO Supplemental Braking System Draw Power from Vehicle Battery
    The SMI DUO part # SM99251 will draw power from your 2016 Jeep Wrangler battery to operate so what you can do is run a charge wire from the positive post of your battery to the 12 volt accessory pin of your tow motorhome's trailer connector like you mentioned. This will keep the battery maintained while you are flat towing. For 10 gauge wire we have the part # 10-1-1 which is sold by the foot. The 1:00 pin of the 7-way will be the 12 volt circuit. I attached an install video for this...
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  • Installation Instructions for SMI Stay-IN-Play DUO Supplemental Braking System SM99251
    All of the flat towing braking systems that work with your 2011 Suzuki SX4 are shown on the linked page. For the SMI Stay-IN-Play DUO Supplemental Braking System # SM99251 the installation instructions are linked for you. I also linked an installation video (showing a different car) that will let you see the whole process.
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