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

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

Item # SM99251
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Tow Bar Braking Systems

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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 or call 1-800-496-5010 for expert service.
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  • Reviews (345)
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Demco Tow Bar Braking Systems - SM99251

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

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   (345 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.

2014 Honda CR-V

After watching the excellent installation video I had very little trouble installing this product. I like the fact that it is a stay-in-play system that literally requires only the flip of a switch to activate. The major components are all installed out of the way, yet are still easily accessible. As for the braking system itself, I find it operationally excellent and believe this product choice was a great one.


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.

Im not in the car when it works, but the indicator light comes on so I assume they work. Honestly, my motorhome is so big I cant tell if there working or not, mostly I stalled to be legal and safe. I like it.
David - 10/21/2021


2013 Jeep Wrangler Sport. No surprises. Some cramped work at brakes pedal. Fit the operating box over the battery with foam on the bottom and screwed to plastic bracket. No rattles. Wiring and hoses were not complicated, but take care and time. Fired on first pull. Take time with the wiring. Routing is important for a clean installation. Took about 4 hours, but i was not in a hurry.

Still going strong!
Michael - 03/31/2022


1950's technology that sort of works. Really no way to fine tune the braking pressure in spite of the sliding screw "adjustment". I tow a Jeep Wrangler 4 door. I have towed it with and without this system. There is some difference but not at all like having electric trailer brakes that you can test and modulate from the cab.

You can adjust the sensitivity of the inertia-sensing mercury switch with a knob on the front of the G-Force controller. 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.
-- Etrailer Expert Jenny N - 03/14/2022

2015 Ford Five Hundred

Installation was challenging. If you're not comfortable with working on vehicles, I would recommend you let a pro handle it. We installed on a Fiat 500, and the biggest issue was that there was very little room to work with. They include plenty of wire, hose, and connectors, but it would be better if they included shrinkable butt connectors since a lot of the wiring takes place in the engine compartment. Breakaway switch mounts horizontally, so you may need a 90-degree angle bracket to adapt from your base plate. For a Fiat, we needed to purchase a separate brake light switch because it isn't practical to wire into the car's switch. I also wish that the kit included a charging cable because the braking system runs off of battery power, and it will likely drain on long trips.

Once installed, this is an elegant solution. Just turn on the switch, hook up, and go. Tons of up-front work for an easy breezy payoff over time.

Jeep Wrangler

Install is a project. Had a couple of questions during installation. etrailer folks are very knowledgeable and helpful. There was one question they could not answer, and the tech gave me Demco's number, and Demco cleared up my issue quickly. I had hard time deciding on placement of Stay-n-play operating box(not much room in engine compartment on 2021 Jeep Wrangler). Choose to install on top of fuse box. Worked well.

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

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


I personally installed this on my 2020 Jeep Wrangler and have towed it using this braking system over 4K miles and have had zero issues. Would definitely recommend! The installation instructions were well written and included an easy to read wiring diagram making is easy to install and the very knowledgeable etrailer support was a bonus too!

Saturn Relay

This braking system has worked very well and is effortless to enable and disable. One thing I would encourage users to do is to determine all accessories that will be needed for the install (I.e. brake light relay, indicator light on coach dash, wiring kit, etc). Pulling all of the needed wires thru the firewall at one time is much easier. Don’t ask how I know this LOL

I would recommend this product


We’re rookie RV ers. I called etrailer on Monday and worked with Melissa T. To put together a order for the parts and wiring needed to flat tow a vehicle behind our RV. I thought we need 3 items but Melissa was very knowledgeable and walked me through what we would need. She explained what everything was and suggested alternatives. I felt comfortable working with Melissa and would recommend her to others! On Thursday I received my order confirmation via email and about 15 minutes later, UPS delivered my order. Placed order on Monday and had it in my hands on Thursday. Not bad!


Love it, Love it, Love it! Everything is hidden away, and even under hard braking, my 1/2 pick-up brakes come on as needed and there is no forward push on my motorhome.

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!

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!


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.

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.


Installation does take alot of additional kits due requirement of Jeep to disconnect battery. Very pleased with system. Wiring print was a real plus and online video


We wired this into a 2017 Ford CMax and it has worked ideal braking system, just switch it on when connected to our motor home and we are ready to go. We mounted the unit behind the drivers seat in a floor compartment to keep it dry and it has worked perfect. It was a little tricky to get the toad indicator light to work, required a separate switch kit to be purchased but once that was wired in we can see the brake pedal indicator lighting up and know that our unit is working as it should.

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


Works well consult with your installer about where parts will be mounted ours put the on off switch in a place where it can be accidently turned on.


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.


I ordered a Falcon II tow bar, Base plate for a GMC Canyon, Demco Stay-n-play braking system and safety cables. worked exactly as it should, directions were easy to follow. All hardware was included. This system allowed us to tow our Canyon 10K miles around the country. super easy to use and I was able to connect and disconnect in less than 5 min. I liked the system enough that I bought the same setup for our new vehicle.


The instructions were written well, if it was written to my trucks package they would perfect, once installed I had an issue with one part but the customer service was knowledgeable and happy to help, received the new part and the system worked as promised.

2019 GMC Terrain

This has been installed in our 2017 GMC Terrain for a year, we have navigated numerous highways and country roads, even did the I-40 stretch by Ashville, with super steep grades, this has performed flawlessly, hook up requires a flip of a switch and away we go. Never do we feel any tug or push, the Terrain brakes nicely and nothing to install and remove each time, disconnect tow bar, flip a switch and you are driving towing behind a 2019 Tiffin 36UA

Show More Reviews

See what our Experts say about this Demco Tow Bar Braking Systems

  • Is One Time Fuse Blowing of SMI DUO Braking System Something to Worry About
    A one time fuse blowing of your SMI DUO part # SM99251 is most likely an anomaly that would be nearly impossible to track down. If you don't see the fuse blow again I'd just chalk it up to a bit of bad luck in that moment and not worry too much about it. I don't think your heat shield idea is terrible, if it would give you some peace of mind you may as well try it.
    view full answer...
  • Where To Install Operating Unit Of Demco Stay-IN-Play in GMC Sierra 1500 and Vacuum Line Location
    Since we have not yet had a chance to install the Demco SBS Stay-IN-Play DUO part # SM99251 on the 2020 GMC Sierra 1500 it is hard to say where to install the operating unit in the engine compartment. The operating unit does need to be installed away from any extreme heat source and the connections must be easily accessible. The unit can often be installed behind the grill provided it doesn’t restrict air flow to the radiator. Moisture will not harm the unit, but it should not be in the...
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  • Whats Best Tow Bar Supplemental Braking System for 2018 Jeep JK Wrangler Unlimited
    The easiest to install and best performing permanent install style of supplemental braking is the DUO part # SM99251 by far. It's what I would recommend for you. We had chance to install this on a 2018 Wrangler like yours and we found there were no issues with the brake pedal either. Check out the attached install video for more info on this.
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  • Where Do 10 Amp Diodes Go When Installing Demco SBS Stay-IN-Play DUO Supplemental Braking System
    The 10 amp diodes of the Demco SBS Stay-IN-Play DUO Supplemental Braking System # SM99251 are only needed if your tow wiring harness is not diode-protected, though most are. In case it 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 a cut out from the linked instruction manual which shows this.
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  • Does the Monitor Light on the SMI Stay-IN-Play DUO Stay on All the Time
    The monitor light included in the SMI Stay-IN-Play DUO Supplemental Braking System part # SM99251 will illuminate when the vehicle is not in tow if power to the controller is still active. You will need to cut power to the controller via the toggle switch each time you remove the vehicle from the motorhome.
    view full answer...
  • Monitor Light for the SMI Stay-IN-Play Wont Turn On
    I looked through the owner's manual for the SMI Stay-IN-Play DUO Supplemental Braking System part # SM99251 and did not see any sensitivity settings for the monitor light. However, I do believe I know that the problem is. Do the brake lights in your toad illuminate when the vehicle is off? If they don't then you will need a stop light switch kit and I would need to know the year, make, and model of your vehicle in order to recommend one. If they do illuminate then odds are you may just...
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  • Troubleshooting 2015 Jeep Grand Cherokee Going Into Park When Hooked Up to Trailer
    It sounds like your 2015 Jeep Grand Cherokee is equipped with ParkSense and the trailer might be triggering the sensors on this system, which is in turn activating this function on the vehicle. When towing a trailer, you will want to disable ParkSense. I took a look at the online version of your Jeep's owner's manual and it looks like this can be disabled by simply pushing the ParkSense switch on your dash. When pushed, the instrument cluster should display "PARKSENSE OFF". It will remain...
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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.
    view full answer...
  • Installing SMI Stay-In-Play DUO on Vacuum Line for 2018 Jeep JL Wrangler
    I spoke with my contact at SMI regarding the vacuum line on your 2018 Jeep JL Wrangler, as it is indeed bit different than previous model Wranglers. He said that when installing the vacuum portion of the Stay-IN-Play Braking System # SM99251 you will just cut the hard plastic 8mm line like normal and install the included 3/8 inch vacuum hose. They also recommend using a worm clamp for a more secure connection. My contact sent along a few pictures from a JL Wrangler installation that they...
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  • How to Mount the G-Force Controller on a 2018 Ford Explorer
    Per the owner's manual for the SMI Stay-IN-Play DUO Supplemental Braking System part # SM99251, the G-Force Controller will need to be mounted within the passenger compartment of the vehicle with the Demco logo level and facing towards the passenger side of the vehicle. Therefore no, the G-Force Controller cannot be mounted in the engine bay compartment vertically. If you would like to learn more about mounting the G-Force Controller I have attached a copy of the owners manual for you....
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  • Supplemental Braking System Recommendation for 2018 Chevy Sonic
    The best supplemental braking system we have for your 2018 Chevy Sonic is the SMI DUO part # SM99251. This is a permanent install kit which means you install it once and you're set and don't have to reset up a system every time you want to flat tow. It's our installers favorite kit because of how much easier it is to install over the other similar kits and because of how well it works. I attached an install video for this kit on a similar 2014 Chevy Sonic as yours. I also attached a video...
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  • Engine Light On and Cruise Control Doesnt Work After SMI Stay-IN-Play Install on a Jeep Cherokee
    I spoke to my contact at Demco about the issue you are having with the SMI Stay-IN-Play DUO Supplemental Braking System part # SM99251 on your 2015 Jeep Cherokee. They stated that this could be caused by either splicing into the wrong stop light switch wire or a check valve has been installed backwards. If you had a shop install the unit then I would take it back to them immediately otherwise you can follow the steps below. If you take a look at page 8 in the instruction manual for the...
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  • How Do I Get Through Firewall to Install Flat Towing Break Away Switch on 2019 Ford Ranger
    Unfortunately we do not sell RVI Flat Towing products, so we have not installed this specific product on any vehicles but we have installed supplemental braking systems like the SMI Stay-IN-Play DUO # SM99251 on a 2019 Ford Ranger. I've provided a link to our installation of an SMI Stay-IN-Play DUO Supplemental Braking System on a 2019 Ford Ranger that talks about wiring through the firewall; you'll want to fast forward to around the 6:00 mark where it shows where the best spot our installation...
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  • If Sensitivity of SMI DUO is All the Way Up will Brakes Pulse with Turn Signals
    I checked with Demco and what you have experienced is normal. With the sensitivity all the way up the brakes will pulse with the turn signals. But since that isn't the setting you'd use it won't be an issue.
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  • Is Brake Light Switch on 2019 Jeep Grand Cherokee Accessible for Stay-IN-Play DUO Installation
    Good question; so the issue with your 2019 Jeep Grand Cherokee is that it doesn't technically have a traditional stop light switch, which is why you are having trouble getting 12 volts. The good news is the Stay-IN-Play DUO Supplemental Braking System # SM99251 does not need your Jeep to have the stop light switch to connect to. As you can see by the cut out of the linked instructions I added, the red wire only needs to be "attached to the blue wire which is between the breakaway switch...
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  • 2016 Chevy Colorado with Diesel Engine Compatibility With SMI Stay-In-Play Duo Braking System
    Your 2016 Chevy Colorado Diesel uses the same vacuum lines as the gasoline engine, it just uses an electric vacuum pump. I reached out to my tech contact at Demco/SMI and the SMI Stay-IN-Play DUO Supplemental Braking System # SM99251 is absolutely compatible and will even install in the same exact way as the gasoline model. I've attached a video to assist.
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  • Time to Set Aside for SMI Duo Supplmental Braking System for 2016 Jeep Wrangler
    I would set aside a long afternoon/evening to install the SMI DUO part # SM99251 in your 2016 Jeep Wrangler Sport. It's not a super difficult or time consuming install but it would take a decent amount of time. If you check out the install video I attached below you'll see us installing it in a Wrangler just like yours.
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  • Troubleshooting SMI DUO Braking System that Doesn't Work with Tow Bar Wiring that's Wired Wrong
    First you need to get the wiring issues you have sorted out and then most likely the DUO will start working like it should. Without knowing what type of connector your tow vehicle is using the best option I have is for you to check out the help article I attached below where you can see all of the standard wiring diagrams that you'll need to make sure your wiring matches. Let me know what you have and whether your connectors are wired properly.
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  • Is Supplemental Braking Required when Flat Towing a 1998 Hyundai Elantra Behind a Motorhome
    Most states (with the exception of Missouri for some reason) now require supplemental braking on the vehicle being flat towed. One of the preferred systems for our installers and what I recommend is the SMI Stay-IN-Play DUO proportional system, # SM99251. It will apply the vehicle brakes in proportion to how much the tow vehicle is braking. This is the safest way to stop and it reduces wear and tear on both vehicles. It is possible that the 1998 Hyundai Elantra was equipped with this or...
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  • Installation of Demco Stay-In-Play DUO in 2007 Hummer H3
    If you don't have room installing the SMI Stay-IN-Play DUO Supplemental Braking System # SM99251 near the emergency brake pedal, I recommend trying lower to offer emergency brake pedal clearance. If it still won't work then it is recommended to install on the console side of the passenger seat in a similar way with the sticker facing the passenger and the switch facing the rear of the vehicle. If those areas will not work for your 2007 Hummer H3, then I recommend trying the console further...
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  • Recommended Supplemental Braking System for 1997 Toyota Rav4
    Without having an air brake system on your motorhome, you will not be able to utilize that braking system. A compressor when you have hydraulic brakes would not be able to cycle fast enough to give you the pressure needed and you would need a release mechanism as well. As an alternative, I recommend the SMI Stay-IN-Play DUO Supplemental Braking System # SM99251. This is a proportional braking system that will apply the brakes to your Rav4 at the same time and with the same intensity...
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  • Does SMI DUO Tow Bar Braking Kit Fit Gas Versions of 2018 GMC Canyon Same as Diesel
    The braking system is the same between the gas and the diesel versions so the SMI DUO part # SM99251 is going to install the same. The install video we have is for a 2015 which is mainly the same as your 2018 but there are a few little differences like you mentioned. The overall process though is the same.
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  • Will the SMI Stay-IN-Play DUO # SM99251 Fit a 2018 Jeep JL Wrangler
    The SMI Stay-IN-Play DUO # SM99251 is actually a universal supplemental braking system so it will be compatible with your 2018 Jeep JL Wrangler. If you check out the attached installation video of this system on a 2017 Jeep Wrangler you can see that the only time this system really connects to your vehicle is for the ground (to a bare metal surface) and your battery for power. At this time (February of 2018) we have not been able to test fit very many products on a 2018 Jeep JL Wrangler...
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  • Troubleshooting 2018 Jeep Grand Cherokee Automatically Braking When Backing Up with Trailer
    It sounds like the trailer might be triggering the automatic braking feature on your 2018 Jeep Grand Cherokee. The vehicles brakes are automatically applied and released when going in reverse and the sensors detect a possible collision with an obstacle, and the sensors are mistaking the trailer for a potential obstacle. I took a look at the online owner's manual for your vehicle and it looks like you can override the automatic braking function by pressing the gas pedal, turning the ParkSense...
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