Don’t Break The Law! Auxiliary Brakes For Flat Towing Cars

When Do You Have To Have An Auxiliary Braking System For A Towed Car?

You might think a car trailing behind your RV wouldn’t put much strain on the brakes. But most states have strict rules about flat towing, and many actually require your towed vehicle to have its own auxiliary braking system plus a break-away device.

The good news? There’s no shortage of options. Portable units sit on the floor and press the brake pedal for you. Hardwired systems take more effort to install but stay hidden permanently, just unhook and drive.

In this article, I’ll walk you through each type and highlight the best auxiliary braking systems for flat towing behind an RV, so you can stay safe and legal no matter which state you roll through.

• Best Portable Option: Blue Ox Patriot Brake | #1_Blue_Ox_Patriot_3_Brake_System | At just 6.2 lbs with no air tanks or hoses to deal with, the Blue Ox Patriot Brake delivers reliable proportional braking with the easiest setup of any portable system on the market. | View on Amazon
• Best Permanent Install Option: Demco Air Force One | #6_Demco_Air_Force_One_Braking_System | The Demco Air Force One taps directly into your coach’s air brake system to deliver 100% accurate proportional braking with no moving parts, no daily setup, and unmatched safety features, the gold standard for motorhomes with air brakes. | View on Amazon

Table List

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	Model	Type	Weight	Power Source	Break-Away Included	Professional Install	Link
	Blue Ox Patriot 3	Portable	6.2 lbs	Electric	Yes	No	Amazon
	Roadmaster Even Brake	Portable	22.3 lbs	Air Compressor	Yes	No	Amazon
	Hopkins Brake Buddy Select 3	Portable	12 lbs	Air Compressor	Yes	No	Amazon
	Hopkins Brake Buddy Stealth	Permanent	n/a	RV Power	Yes	Yes	Amazon
	Roadmaster Invisibrake	Permanent	n/a	RV Power	Yes	Yes	Amazon
	Demco Air Force One	Permanent	n/a	Coach Air Brakes	Yes	Yes	Amazon

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Best Portable Braking Systems

One of the most popular auxiliary brake styles for flat towing is a compact unit you place on the floorboard in front of the driver’s seat. A mechanical arm hooks to the brake pedal, and the whole thing runs off a 12V plug.

Most of these systems are proportional, meaning they match whatever braking pressure your RV applies. There’s a wireless monitor with an inertia sensor that sits in your coach, reads the deceleration, and tells the unit in your towed car how hard to press.

These setups are popular for good reason. They’re easy to install, can be moved between vehicles, and can be resold when you’re done with them.

The main downside? That inertia sensor isn’t perfect. Occasionally you’ll get “false braking” where the towed car brakes even though the RV isn’t slowing down. It’s rare, but it happens.

Here are some of the best portable auxiliary braking systems on the market.

1. Blue Ox Patriot 3 Brake System

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My Review

The Blue Ox Patriot Brake is probably the most popular portable flat tow braking system out there, and for good reason. At just 6.2 lbs, it’s significantly lighter than previous versions and most competitors, which makes setup and storage a breeze.

The all-electric design means there’s no messing with air compressors, tanks, or hoses. Just attach the brake claw, plug in the power cord and break-away switch, hit the setup button, and you’re ready to roll. The unit cycles once to confirm everything’s working, then the indicator light lets you know you’re good to go.

What I really appreciate is the dash-mounted wireless controller. You can monitor brake function, adjust braking force, or manually override the system without leaving your seat. The proportional braking mimics an actual foot on the pedal, so stops feel smooth and natural rather than jerky.

It fits virtually any towable vehicle without special brackets, which is huge if you swap between cars or upgrade down the road.

2. Roadmaster Even Brake System

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My Review

The Roadmaster Even Brake is a rock-solid portable option that’s earned a loyal following among full-time RVers. What sets it apart is the constant self-diagnostic monitoring, this thing checks itself so you don’t have to.

A quick glance at the wireless monitor tells you exactly what’s happening with your brakes at any moment, with LED lights for quick status checks and LCD text that spells out the details.

The proportional braking is smooth and responsive, matching your motorhome’s stops rather than slamming the brakes at one preset level. I’m a fan of the ‘Terrain-Sensing Logic’ feature, which automatically levels the unit on hills or rough ground so braking stays consistent.

The built-in low battery warning is a nice safety net too, it alerts you when voltage drops, then shifts into sleep mode to preserve emergency braking power.

Setup is dead simple: position it between the seat and pedal, adjust the clamp, slide your seat forward, plug in, and hit the test button. The air compressor recovers quickly between stops, and the adjustable pedal clamp fits brake pedals that other systems struggle with.

3. Hopkins Brake Buddy Select 3 Brake System

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My Review

The Brake Buddy Select 3 brings something to the table that none of the other portable systems on this list offer: a built-in 15-amp battery charger. If you’ve ever worried about your towed vehicle’s battery draining on a long haul, this solves that problem completely. The charger keeps the battery topped off while you drive, so you never have to pull over and idle just to get some juice back.

Beyond that, it’s a well-thought-out unit. The AutoStart feature runs a diagnostic check and cycles the brake pedal automatically at startup, which also helps prevent flat-spotting on your tires. The Quick-Lock clevis is genuinely versatile, it locks down securely on brake pedals that give other systems trouble.

Setup is streamlined with the Easy-Pull single cord that handles both power and break-away connection. At just over 12 lbs with a foldable carry handle, it’s easy to move around and store. The interactive remote lets you tweak settings from inside your coach and sends instant alerts if anything needs attention.

Hopkins also has a reputation for solid customer support, which matters when you’re troubleshooting on the road.

Stealth/Hide-Away Braking Systems

If you flat tow regularly and you’re tired of hauling out a portable unit every single time, a stealth braking system might be worth the investment.

These setups require more involved installation, usually professional, but once they’re in, you never have to touch them. Unhook from your RV and drive away. No boxes to remove, no cords to unplug, nothing to store.

The typical setup involves a control box hidden somewhere in the vehicle (behind a seat or in the trunk), a vacuum pump mounted under the hood, and a cable-and-pulley system that pulls the brake pedal from underneath. Everything stays out of sight.

The trade-off is clear: more work upfront, but zero hassle down the road. If you’re committed to one tow vehicle for the long haul, these systems are hard to beat.

Here are some of the best stealth auxiliary braking systems for flat towing.

4. Hopkins Brake Buddy Stealth

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My Review

The Brake Buddy Stealth is for folks who are done messing with portable units every time they hook up. Once it’s installed, everything stays hidden, the main unit tucks behind a seat or in the trunk, the vacuum pump lives under the hood, and a cable-pulley system handles the brake pedal from underneath.

When you’re ready to tow, just connect the All-In-One Adapter between your motorhome and towed vehicle and you’re rolling. No boxes to haul out, no cords to arrange, nothing.

What really sets this apart is the Dual Controller. It’s the only system I know of that works for both flat towing a dinghy and pulling a traditional trailer, just switch modes with a button. You get full control from the driver’s seat, including sensitivity adjustments and a manual test function.

The system draws power from your RV, so you won’t drain your towed vehicle’s battery on long trips. Installation is more involved than portable options (professional install is recommended), but Hopkins claims it goes in up to 5x faster than other permanent systems. Once it’s done, it’s done, just plug in and drive.

5. Roadmaster Invisibrake Hidden Power Braking System

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6. Demco Air Force One Braking System

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My Review

If you have a motorhome with air brakes and you flat tow frequently, the Demco Air Force One is the gold standard. This system taps directly into your coach’s air brake signal to deliver truly proportional braking, not the inertia-based approximation you get from portable units.

When you brake the motorhome, the towed vehicle brakes with the exact same intensity. No adjustments, no calibration, just perfect symmetry every time. The operating unit has no moving parts, which means there’s essentially nothing to wear out or maintain. It mounts under the hood and stays completely invisible.

What really sets the AFO apart is Total Coach Protection. In the event of a separation, the system seals off your coach’s air supply so your motorhome can still stop normally, a federal safety requirement (FMVSS 121) that other air-operated systems don’t address.

Demco’s patented actuator is also worth mentioning, it installs with a single self-drilling screw and uses a linear force design that eliminates the binding and cable hang-ups you sometimes see with pulley-based systems. The whole setup transfers to a new tow vehicle without buying new parts (just a cheap reinstall kit), which is a nice touch if you upgrade down the road.

The catch? Your RV needs air brakes. If you’ve got a smaller rig with hydraulic brakes, this one’s not for you.

Which Supplemental Flat Tow Braking System Is The Best For Me?

Choosing the best auxiliary braking system really comes down to how you travel and how long you plan to keep your current setup.

If you switch vehicles every few years or you’re just getting into RVing and aren’t sure how long you’ll stick with it, a portable system makes the most sense. The Blue Ox Patriot Brake is lightweight, all-electric, and transfers between vehicles in minutes. If battery drain on long trips concerns you, the Hopkins Brake Buddy Select 3 has a built-in charger that solves that problem. And if you want a system that constantly monitors itself and adjusts to terrain automatically, the Roadmaster Even Brake is a solid pick.

If you tow all the time and you’re committed to your current vehicle, a permanent hidden system is worth the upfront investment. The Hopkins Brake Buddy Stealth is a great option if you also pull trailers, its Dual Controller handles both. The Roadmaster InvisiBrake is about as hands-off as it gets: no switches, no buttons, just plug in and go. And if your motorhome has air brakes and you want the best braking performance money can buy, the Demco Air Force One delivers true proportional braking that no inertia-based system can match.

No matter which direction you go, having a supplemental braking system is safer and, in most states, required by law. It protects your RV’s brakes from excessive wear, shortens your stopping distance, and keeps your whole rig stable during deceleration.

If you’re planning to travel across state lines (and let’s be honest, that’s half the fun), you’ll want to be covered no matter where you end up.

Flat Tow Braking Systems: FAQ

Do I really need a supplemental braking system for flat towing?

In most cases, yes. 49 US states and all Canadian provinces require some form of supplemental braking when you’re towing a vehicle behind a motorhome.

Beyond the legal requirements, it’s a safety issue. The added weight of a towed vehicle increases your stopping distance and puts extra strain on your RV’s brakes. A supplemental system reduces wear on your motorhome, shortens stopping distances, and keeps the whole setup stable when you hit the brakes.

What’s the difference between proportional and non-proportional braking?

Proportional braking systems match the braking intensity of your motorhome, brake lightly and the towed vehicle brakes lightly; brake hard and it brakes hard. This makes for smoother, more natural stops.

Non-proportional (or “on-off”) systems apply a preset amount of braking pressure every time, regardless of how hard you’re stopping. Proportional systems are generally considered safer and easier on your towed vehicle’s brakes.

What’s a break-away system and why do I need one?

A break-away system automatically applies the brakes on your towed vehicle if it separates from the motorhome. It’s a critical safety feature and required by law in most places. If your tow bar fails or the connection comes loose, the break-away brings your towed car to a stop instead of letting it roll freely into traffic. Most quality braking systems include one.

Will a portable braking system drain my towed vehicle’s battery?

It can. Most portable systems draw power from the towed vehicle’s 12V outlet, which means on long trips your battery could run low. Some systems (like the Hopkins Brake Buddy Select 3) include a built-in battery charger to prevent this.

Others (like the Roadmaster Even Brake) have low-battery warnings that alert you before things get critical. If you tow long distances regularly, look for a system that addresses battery drain.

Can I use the same braking system on different vehicles?

Portable systems, yes. That’s one of their biggest advantages. Units like the Blue Ox Patriot Brake and Roadmaster Even Brake can be moved from one vehicle to another with minimal hassle.

Permanent/stealth systems are a different story. They’re installed into a specific vehicle and aren’t designed to be transferred, though some (like the Demco Air Force One) offer low-cost reinstall kits if you get a new tow vehicle.

Do these braking systems work with hybrid vehicles?

Most of them do. The Blue Ox Patriot Brake, Roadmaster Even Brake, Hopkins Brake Buddy Select 3, Hopkins Brake Buddy Stealth, Roadmaster InvisiBrake, and Demco Air Force One are all compatible with hybrids. That said, it’s always smart to double-check compatibility with your specific vehicle before purchasing.

What’s the difference between portable and permanent (stealth) braking systems?

Portable systems are self-contained units you place on the floor of your towed vehicle each time you tow. They’re easy to set up, easy to transfer between vehicles, and don’t require professional installation. The trade-off is that you have to install and remove them every trip.

Permanent (stealth) systems are installed once and stay hidden in your vehicle. There’s nothing to set up or take down, just hook up to your motorhome and go. The downside is they require professional installation, cost more upfront, and don’t transfer easily if you change vehicles.

Do I need professional installation for a stealth braking system?

It’s highly recommended. Stealth systems involve mounting components under the hood, running cables and wiring, and sometimes tapping into your vehicle’s vacuum system. If you’re not comfortable with that level of work, a professional installer will make sure everything is done correctly and safely.

What if my RV doesn’t have air brakes?

If your motorhome uses hydraulic brakes (most Class B and Class C rigs, plus smaller Class A units), you’ll want to stick with portable systems or stealth systems like the Hopkins Brake Buddy Stealth or Roadmaster InvisiBrake.

The Demco Air Force One specifically requires your coach to have air brakes, so it’s only an option for larger Class A motorhomes equipped with that system.

How do I know which system is right for me?

Ask yourself a few questions:

• How often do you flat tow?
• How long do you plan to keep your current tow vehicle?
• Does your motorhome have air brakes?
• Do you want to handle setup yourself or prefer a plug-and-go solution?

If you tow occasionally and might switch vehicles, go portable. If you tow constantly and you’re committed to your current car, a stealth system saves time and hassle. And if you’ve got air brakes and want the absolute best braking performance, the Demco Air Force One is the top choice.