RV Living

How Do RV Electric Brakes Work?

Electric brakes in an RV are easy to operate, and with a small force, a driver can control thousands of pounds of the RV or towed vehicle.

How Do RV Electric Brakes Work? A brake controller is installed near the dashboard that governs electric brakes’ operation in an RV or towed camper. When the driver presses the brake pedal, voltage applies to the electromagnet in the brake assembly. It actuates a lever to push away rear and front shoes depending upon your RV’s moving direction. As a result, the pressure on the braking drum causes the wheels to stop. 

How Do RV Electric Brakes Work?

Brakes are an essential part of a vehicle to control it while traveling. A sound braking system for your RV is an assurance of safe traveling and a smooth ride to enjoy your camping experience.

Moreover, when towing a trailer or camper behind a truck or you tow a vehicle or car behind your motorhome, you need an efficient braking system in all these scenarios to control your vehicle and avoid any accident. 

These are low cost, easy to install, and have readily available comparatively inexpensive spare parts.

A brake controller installed in the camper commands its operation, and the driver can manually operate the brakes through his hand via a brake controller.   

Parts of electric brakes

There are eight major parts of the electric brake assembly of an RV. They are:

ElectroMagnet

It is the main difference between hydraulic brakes and electric brakes. It consists of a coil wound on ferromagnetic material to make it a magnet when an electric current passes through it.

Common materials used for the core are iron, chromium, etc. 

One face of the magnet has abrasive material to provide friction when it comes in contact with the rotating drum or armature during a braking operation.   

Hollow Shaft

It is a hollow area in the center to mount it on the RV axle. You can use it on the inside of the wheel of your trailer to use it. 

Actuator

It is a semi-circular piece of metal connected with an electromagnet on one side and brake shoes on the other side with springs’ help.

Its purpose is to transfer the electromagnet’s force mechanically to the assembly’s braking elements to stop or reduce RV or trailer speed.

It is also called an actuating lever. Its material of construction is cast iron that gives it strength.

Larger Rear shoe

It is installed on the backside of the brake assembly and has a semi-circular shape. It consists of two steel pieces joined together by welding.

Some frictional material, mostly asbestos fibers called brake lining, is bonded on the shoe’s surface.

Its top anchors with reactor springs and the bottom with an adjuster spring. Its other name is secondary or trailing shoe.

Its rear shoe is slightly larger than the front shoe.

The reason is that there is a more significant force on it during the braking operation as the rotating drum tries to turn them in its rotation direction. 

Smaller Front shoe

It has a similar shape and material as that of the rear one. The only difference is that it has a slightly shorter and thicker lining as the back shoe performs most of the braking operation. It is also called primary or leading shoe.

Springs

There are three types of springs that have essential roles as part of these brakes. They are brake shoe hold-down spring, adjuster spring, and reactor spring.

Hold down springs keep both the front and rear shoes attached with the brake assembly’s backing plate.

Instead of fixed screws, flexible springs enable us to allow the shoes’ movement while keeping them in their place in the backing plate. Sometimes you will find steel clips instead of springs to serve the purpose.

Adjuster spring helps to maintain the clearance between the brake shoes and the drum. You can manually adjust its tension according to the requirement.

Some brakes have a self-adjusting mechanism to adjust the spring position.

There are 2 reactor springs, one with each shoe. It serves to have controlled the amount of force on the shoes and restores their original position after the brake is released.

Springs have an essential role in the brakes’ overall operation, but due to their elastic nature and frequent use, they are the most replaced part due to wear and tear.

Armature/Drum

It is a hollow cylinder slightly larger than the brake assembly mounted on the wheel hub.

It rotates with the wheel during the vehicle’s movement, and brakes interact with wheels via these drums. Its material of construction is often cast iron; however, modern designs with aluminum are also available.

Its surface should be strong enough to withstand the high heat produced during a braking operation.

Moreover, its exterior has fins or protruded spikes to increase the surface area for efficient cooling.

Due to friction between magnet, brake shoes, and drum, its surface reduces with time.

Therefore, you should check the maximum diameter or minimum thickness of the drum on its surface and should not use it beyond the limit mentioned on the drum. 

Aluminum drums are lightweight, have better heat dissipation, and smooth round shape, but they are expensive than the cast iron ones. 

Brake controller

It is the brain of the electric brakes and controls the whole braking operation.

It consists of electronic components that receive signals from sensors installed with brakes and sends signals to the electromagnet to activate.

Its functions include brake gain settings to apply appropriate voltage according to requirement, its’ sensitivity and displays the brakes’ status.

Moreover, a driver can manually activate the brakes by pressing a button on the controller.

They come in two types based on their mechanism of operation. They are time-based activation and inertia-based activation.

The time-based controller applies increasing power to the brakes with time according to the gain settings.

There is a linear relationship between applied current and time. This mechanism is not accurate and smooth for different driving conditions.

Inertia-based or proportional time controller takes input from a sensor installed with the wheel called accelerometer and applies power according to the RV’s momentum or speed and tilt angle.

It has excellent performance and smoothly performs the braking operation according to the speed and terrain, whether it is a hilly area or smooth surface.

Installation of the brake controller is easy, but you need to adjust its settings according to your requirement and efficient braking operation.   

Color coding of wires with electric brakes

Four wires originate from the brake controller and end on the magnet, stop lights, and brake assembly.

Each wire has a different color according to its function. The table given below depicts the color of each wire from the brake controller and its purpose.

Color Purpose Wire Gauge
White Ground (-), connected with the negative terminal of battery or body of the RV > 12AWG
Black 12V (+), connected with the positive terminal of the battery via a circuit breaker >12AWG
Red Stoplights 16AWG
Blue To brake magnet >12AWG

Although electromagnet is insensitive to the applied voltage, the brake controller is an electronic device, and its components are sensitive to the applied voltage.

Therefore, be cautious while connecting the white and black wires to the brake controller as reversed polarity can damage it.

Modern RVs come with all the wiring and have 7 pin connectors available. You plug the one end of the connector in the towing vehicle and the other side in the trailer or camper.

Working principle of RV electric brakes

When the driver presses the brake, its controller applies appropriate voltage to the magnetic coil to make an electromagnet.

A magnet’s strength depends on the applied voltage that depends on applied force, load on RV or trailer, speed, and vehicle angle. 

Electromagnet gets attracted towards the rotating drum. As the magnet rotates with the drum, it activates the lever that pushes the brake shoes against the drum surface to decelerate the vehicle. 

Although the power transmission mechanism from the driver’s press to brake assembly is the electric current, the stopping force or torque is still applied mechanically to the wheels.

The frictional between the brake shoes and rotating drum acts as the mechanism to slow down the camper.

Size of Brakes and their Capacity

These are available in different sizes according to their braking capacity. You will find their rating defined in terms of diameter. 

The larger the brake diameter, the less the force required by the brake to stop the camper. Smaller diameters have less braking capacity and more power by brakes to perform their operation.

Here is a chart comparing 7,10 and 12-inch brakes, mentioning their size, cost, weight, and braking capacity.

They usually come in pairs for installation on both the driver and passenger sides. Price increases with an increase in size and loading capacity of axle.

Size Weight Braking capacity Cost
7-inch 8-10lbs 2000-3000lbs axles $50-$80
10-inch 20-25lbs 3500-5000lbs axles $100-$120
12-inch 25-30lbs 5000-7000lbs axles $150-$300

 Electric brakes on single axle vs. double axle camper

Double axle campers are more stable to tow than single axle and better choice while traveling long distances. Moreover, they have a higher loading capacity.

You can install these on both axle trailers’ wheels and provide the power supply in parallel with reliable operation.

It requires 2 sets of brakes for installation with all four wheels to ensure safe and efficient braking. All four assemblies will be in parallel to ensure reliable operation if there is a defect in the wiring.

You can save money by installing the brakes on a single axle; install them on the rear axle to ensure smooth and safe operation. Otherwise, your towing vehicle or truck has to do a lot of work while trying to stop.  

Self-adjusting vs. manual adjusting electric brakes

The two types of brakes installed with RVs based on their adjusting mechanism are self-adjusting and manual adjusting brakes.

Both have similar working principles except for their adjustment over time due to wear and tear in the drum and brake shoes. 

Self-adjusting brakes have an adjusting wire running from the top of the brake assembly to the bottom.

Moreover, its adjuster spring is of a different shape than the manual ones. Due to self-adjustment at every forward or reverse stop, brakes operate at their optimum level and perform smoothly and efficiently.

However, they require initial settings at the time of installation. Due to fewer maintenance requirements, you should install self-adjusting brakes to avoid any mishap. However, it will cost you extra money to purchase them.

In case of manually adjusting brakes, you need to remove the plugin front of the lever on the backing plate and move it in smaller increments until you achieve the required braking performance.

It is safe to install identical brake assemblies on a vehicle’s wheels, whether single axle or double axle. One brake can operate before the others in different types, resulting in unnecessary stress on other wheels and towing vehicles.  

Left hand vs. right-hand electric brake assembly

Their assemblies come in pairs as left-hand and right-hand ones. You install the left hand on the driver side and the right-hand brake on the passenger side.

You can differentiate between the two by looking at the brake shoes. The shorter or smaller shoe will always be on the front side. 

Do all RVs have electric brakes?

The government has a weight limit to have brakes installed on the RVs, whether running independently or towed with a vehicle.

Keeping government law aside, it is a safety advice piece to install these on your vehicle linked with a brake controller to ensure a safe and smooth journey if you have to travel frequently and over long distances. 

Do Electric Brakes Work in Both Forward and Reverse Directions?

Yes, electric brakes mounted with your RV can work either trailer is moving in forward or reverse direction.

One of the two brake shoes activates by the actuating lever depending upon the direction of rotation. In this way, these work in either side direction of the wheels.

Power source for electric brakes in RV

The brake controllers come in two voltage settings that are 12V and 24V and draw power from the towing vehicle battery.

What is the power required to operate the electric brakes?

Its power requirements vary according to the gain setting of the brake’s controller and size.

Typical current amperage for 7, 8, and 10-inch sizes are 3-4 amperes to stop the RV.

In the case of a double axle camper, the maximum current that magnets of all four brake assemblies will draw can vary from 12-16 amperes.

Therefore, the installed wiring and circuit breakers should be according to the whole circuit’s maximum amperage.

Preventive measures to avoid locking up of electric brakes

Sometimes electric brakes cease the rotation of wheels while the vehicle is moving. It is called a locking up of brakes.

● Check for proper wiring with no loose or broken connection regularly.

● Remove any rust or corrosion on magnet terminals.

● Properly adjust the gain settings of the controller and get it checked periodically every quarter.

● Perform the manual adjustment of brake shoes to avoid locking state.

● Use a junction kit to make a wiring connection instead of a loose connection by twisting wires.

● Installation of breakaway kit with the towed vehicle will ensure fail-safe operation to avoid any accident.

● Brake drums can capture water inside their surface, resulting in corrosion. 

Installation cost

Electric brakes come in pairs (right hand and left-hand assembly) for both tires mounted on an axle.

They are portable, and you can easily replace them. Their retrofitting in place of hydraulic ones is also easy as you need to install a controller and connect the brakes with it.

Its cost varies according to its size, capacity, and self-adjusting features. The typical price range is $50-$500 for loading capacity ranging from 2000lbs to 10,000lbs. 

Mileage to replace the parts of electric brakes

Parts that undergo high pressures should be continuously checked and periodically replaced.

Few components that need periodic replacement are brake shoes, drum, and magnet as they slide against the drum surface and withstand high temperatures.

There is no specific mileage condition for the replacement of their parts as their condition depends on the usage and preventive maintenance.

Therefore, every time you go to a workshop for some maintenance work, ask the mechanic to inspect all the parts and tell if replacement of any part is required. The minimum period for preventive maintenance is every quarter.  

Are RV brake magnets sensitive to polarity?

The electromagnet works on a 12VDC power supply applied via two wires, one for voltage and the other for ground.

The polarity of both cables does not affect the function of the magnet. You can connect any of the two wires with any electromagnet terminals, and brakes will work fine.

Therefore, the operation of the brake magnet is insensitive to the voltage polarity.

Breakaway Switch in Case of Towed Camper

In case of a towed camper with a truck or any other vehicle, the towing vehicle’s brake controller will control and power up the camper’s brakes.

If somehow the towing link breaks and the RV runs away from the truck, a breakaway kit detects this situation and activates the brakes on the motorhome.

The Breakaway kit contains a battery charger and a small battery. It keeps on charging the battery when the camper is in contact with the vehicle.

It stops by powering up the brakes as soon as it separates from the towing vehicle. It is an additional safety feature to avoid accidents. Therefore, the presence of a breakaway switch is mandatory according to the laws in various USA states.

Its cost can vary from $40-$120 according to the charger rating, battery rating, and other features. 

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