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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
Our Price: $1,175.00
You Save: $432.23
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. Great 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 1-800-940-8924 for expert service.
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  • Reviews (387)
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Demco Tow Bar Braking Systems - SM99251

  • Brake Systems
  • Hydraulic Brakes
  • Proportional System
  • Fixed System
  • Demco
  • 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

Installation Details SM99251 Installation instructions

This Product Fits The Following Vehicles

Customer Satisfaction Score:

Customer Reviews

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

Average Customer Rating:  4.8 out of 5 stars   (387 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

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.

2018 Jeep Wrangler

I purchased my first Demco stay-in-play braking system about five years ago and installed it on a 2017 Chevy Colorado. I removed it when I purchased my new 2021 Chevy Colorado and installed it on it. That Demco braking system is still working great. I recommended the Demco braking system to my son in-law for his 2021 Jeep Gladiator ( which I installed for him ) and he is real happy with it. I just purchased my Second Demco braking system and I installed it on a 2018 Jeep Wrangler and it is working great. If you watch the videos and follow the instructions and have a variety of tools you can install it yourself. Of course my third install was the easiest. All three tow bars and Demco braking was purchased at etrailer. After the first order I placed with etrailer went so smoothly, I will not call anyone else for RV parts. There employees have been fantastic to work with.
I feel that service is the most important, I received my order when told I would get it and pricing is great.
Thanks for the Great Service etrailer. J Rinaldi

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


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

Ford Edge

One year and oner12k miles the DemcoStay-In-Play has worked flawlessly in our 2020 Ford Edge ST. This includes a trip to Colorado and PA. Highly recommend and etrailer is great to do business with.


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.


Works great! I would buy it again. Tow a 2021 Jeep Wrangler, 5400 lb., And glad to have the braking help, especially in the mountains. Low maintenance, no complicated wiring between motorhome and Jeep.


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

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!

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.

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.


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.


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!


Outstanding product and even better customer service! Two backyard mechanics installed baseplate and braking system with just one call to confirm proper wire connection. Total package works great.

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

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


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.


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.


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!


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.


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

Show More Reviews

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

  • Why Doesn't the Stoplight Circuit Used for Install of SMI Stay-IN-Play DUO Come from Trailer Wiring
    The reason you can't use the stop light circuit of the trailer wiring on your motorhome is because that circuit also carries the blinker signal. You have to find a dedicated stoplight circuit and that is why the install instructions recommend you find that under the hood of the towed vehicle. I attached an install video that shows this getting installed in a similar Ford SUV as yours.
    view full answer...
  • Does the Engine Need to Be On So Brakes Work Properly While Flat Towing 2010 Ford Explorer
    No, the vehicle motor will not need to be running while towing the vehicle in order for the brakes to work. When checking the owners manual for an Explorer, I found that if your 2010 Ford Explorer is a 4WD vehicle, Ford recommends that an accessory neutral tow kit be installed on the vehicle in order to flat tow. If a neutral tow kit is not installed, Ford has determined the vehicle should not be towed with all four wheels on the ground. This accessory kit is available through your local...
    view full answer...
  • Easiest and Best Supplemental Braking System for Flat Towing 2016 Jeep Wrangler
    By asking for a smaller model are you talking about a different supplemental braking system that would fit and work better? If so, the best solution would be the SMI DUO part # SM99251 which is our installers favorite kit. It installs the easiest and just works the best all-around. If you check out the install video I attached you can see it installed on a similar 2016 Jeep Wrangler as yours too.
    view full answer...
  • Recommended Installation Location for Operating Unit on SMI Stay-IN-Play DUO for 2016 Kia Soul
    The operating unit for the SMI Stay-IN-Play DUO Supplemental Braking System # SM99251 referenced in your question can be installed in the engine compartment but should be away from any extreme heat source. Also keep in mind that the connections will need to be easily accessible. A good location on your Kia Soul might be behind the grill, as long as it doesn't restrict air flow to the radiator. I have attached the complete installation instructions on this excellent proportional braking...
    view full answer...
  • Comparison Of SMI Stay-In-Play Duo And Roadmaster InvisiBrake Supplemental Brake Systems
    Both the SMI Stay-IN-Play DUO, part # SM99251 and the Roadmaster InvisiBrake Supplemental Braking System, part # RM-8700 are nice braking systems and will function similarly but I recommend the Duo system. Both systems are a one-time installation. The # SM99251 is easier to install because it has a shorter arm that is used in the towed-vehicle where the longer cable used with the # RM-8700 can be tough to find places to mount. I have attached a couple photos that show how the brake pedal...
    view full answer...
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  • Supplemental Brake System Recommendation for 1971 Volkswagen Bus for Flat Towing
    The SMI Stay-IN-Play DUO Supplemental Braking System # SM99251 would be a great option for your 1971 VW Bus as it is brake booster compatible and because it's one of our installers favorite systems to use because of how well it works and how much easier it is to install than other similar setups.
    view full answer...
  • Permanent Install Supplemental Braking System Recommendation for Flat Towing 2005 Honda Element
    The SMI Duo part # SM99251 that you mentioned is going to be your best option. It works just as well as the Inivsi-Brake yet installs much easier. If the permanent install route is what you are wanting the DUO is hands-down the best option. Our installers here love it. If you are paying for an install somewhere it will also be much less expensive to go this route. The Invisi-Brake is also not listed as a fit for your Element either at this time.
    view full answer...
  • Does SMI Duo Supplemental Braking System Drain Vehicle Battery
    The SMI DUO part # SM99251 that you referenced does use the vehicle battery so it would drain the battery after prolonged use. What a lot of people do to combat this is run a 10 gauge wire from the 12-volt accessory circuit of the 7-way on the tow vehicle to the battery on the towed vehicle to keep it topped off while towing.
    view full answer...
  • Supplemental Braking System Recommendation to Tow a 2017 Jeep Wrangler Unlimited
    Our installers here do not care for the Blue Ox Autostops. They complain that the install is difficult and the braking action to be not very noticeable. Our most popular system is the Stay-IN-Play DUO # SM99251. It's a complete install that's permanently on the Jeep but it's easier than many of the others. The best thing is after the intial install you just need to flip a switch to set it up each time you're ready to tow.
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  • One Time Install Recommendation for 2015 Fiat 500 Abarth
    Yes, the SMI DUO part # SM99251 is a one-time setup install supplemental braking system that is a fit for your 2015 Fiat Abarth. Of the braking systems like this the DUO is the one our installers like the best because of the easier install and great braking performance.
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  • Does SMI Supplemental Braking 2016 Ford Fiesta Know Difference Between Turn Signals & Brake Lights
    No as the SMI part # SM99251 is designed to recognize the difference between turn signals and stoplights when determining if the brakes or just the blinkers are being applied. I attached an install video for this braking system on a similar 2014 Ford Fiesta for you to check out as well.
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  • Can Supplemental Braking be Used on a 2008 Ford Escape Hybrid if it has Active Power Assist Brakes
    It depends. Not all supplemental braking systems are compatible with the type of braking systems on some hybrid vehicles. One system that will work on your 2008 Ford Escape Hybrid with power assited brakes is the Stay-IN-Play DUO # SM99251. It's one of our favorite systems here because of how easy it is to use. The installation is more involved than a lot of systems but after that you just flip a switch when you're ready to tow.
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  • Blue Ox Patriot Braking System Give A04 Error and Stays Fully Extended
    I am assuming that you received the same error code on the replacement Patriot braking system which would indicate another software error. The question is, why does this keep happening, since it is unlikely that 2 different Patriot systems would have the exact same problem. It sounds like what might be happening is the Liberty battery is losing voltage over time while you are towing and that is affecting the Patriot system, which is supposed to go into a battery saving mode when it detects...
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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 just...
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  • Supplemental Braking System Recommendation for a 2010 Jeep Wrangler
    Our installers here prefer to install the SMI Stay-IN-Play DUO # SM99251 on most vehicles, including Jeeps. It is one of the lower cost options but works very well and does not require additional accessories like most other systems. Once it is installed you will not have to worry about it again. I have included a link to a video showing an example installation on a similar Jeep.
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  • Is the SMI Stay-IN-Play DUO a Good Quality Supplemental Braking System
    In a word the SMI Stay-In-Play DUO # SM99251 is awesome though the brake pedal monitor leaves something to be desired like you said. There is nothing stopping you from running the power wire for it all the way to the cab of the RV but its LED lights are very bright so keep that in mind. Our shop manager likes the DUO more than the other braking systems that are similar because it is easier to install with smaller components and works really well. I recommend it the most of all of the...
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  • Where is Stoplight Circuit Found on 2015 Chevy Sonic for SMI DUO Install
    You are in luck as we had the chance to install the SMI DUO part # SM99251 in a 2014 Chevy Sonic very similar to your 2015 model. I attached a video that shows the entire install process. In it you'll see that instead of tapping into the stoplight circuit of the vehicle they use the blue output wire on the operating unit instead.
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  • Does Tow Bar Wiring Usually Run Through Interior or Underneath Vehicle
    Sounds like you are referring to the tow bar lighting that a vehicle needs for operating the taillights of the vehicle when it's being towed. Basically you can run the wires in either orientation and it really just depends on the setup. I would say most of the time it makes the most sense to run the wiring on the exterior of the vehicle under it since newer vehicles are getting harder to access grommet holes that feed into the interior.
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  • 20 Amp Fuse Keeps Blowing on the SMI Stay-IN-Play DUO
    I called SMI to see if this was something they had heard of before and my contact said that your 20 amp fuse should not be blowing when you pull the breakaway switch on the SMI Stay-IN-Play DUO # SM99251. What he said you can try to do is swap out the 20 amp fuse for a 25 or 30 amp fuse and check all of your grounds. He mentioned that anytime there is a problem with a fuse it is most likely the ground so that is a good place to start.
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  • SMI DUO or Invisibrake Recommendation for 2005 Jeep Wrangler
    The SMI DUO # SM99251 is the best option for supplemental braking for a vehicle that permanently installs. Our installers prefer this kit to all of the other ones as it's got an easier install and performs really well when flat towing. For your 2005 Jeep Wrangler this would be the best option. I attached an install video for this on a similar Wrangler as yours for you to check out too.
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  • Will SMI Stay-IN-Play DUO Proportional Braking System # SM99251 Work on 2010 Ford Ranger 4x4
    I spoke with my contact at SMI and the mercury switch on the Stay-IN-Play DUO Supplemental Braking System, # SM99251, actually has one contact and will work with your 2010 Ford Ranger 4x4. You will just follow the basic installation instructions with no additional modifications necessary. I have attached these installation instructions for you. The DUO is referred to as a progressive system but has the characteristic of a proportional since it uses inertia. This is a dual signal system...
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  • Where to Make the Vacuum Connection on a 2014 Jeep Cherokee V6
    Since sometimes in vacuum line t-connectors there can be reducers installed in the t-connectors to reduce vaccuum signal I would recommend you install the check valve between the t-connector and the brake booster just to be on the safe side.
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  • Will the SMI Stay-IN-Play DUO Supplemental Braking System # SM99251 fit a 1991 Toyota Truck
    I spoke to my contact at SMI and he informed me that the SMI Stay-IN-Play DUO Supplemental Braking System # SM99251 that you referenced can basically fit any vehicle so it would work well on your 1991 Toyota Truck. I attached an install video for you to check out as well.
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  • Relocating Inertial Sensor of SMI Stay-IN-Play DUO Supplemental Braking System
    The Stay-In-Play DUO works best when the vacuum booster is depleted, so that the pull on the brake pedal is consistent. The first few times you press the brake pedal, they'll still be some residual pressure in the car's braking system. It's recommended that you press the pedal several times before moving off, so that the system applies the brakes with consistent pressure. The switch you mentioned is on the box that serves as the inertia sensor, which needs to be mounted so its level and...
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