Trailer Disc Brake Conversion – Electric Over Hydraulic Disc Brakes – WOW!

There are several types of braking systems available on bumper pull travel trailers and fifth wheel trailers today. Two of the most common are electric drum brakes, a less expensive system, and electric over hydraulic disc brakes which are a bit more costly. We recently converted our 36′ fifth wheel trailer’s braking system from factory installed electric drum brakes to electric over hydraulic disc brakes. What an incredible improvement this upgrade has made in our stopping power and personal safety. The difference is like night and day!!

This page outlines our reasons behind doing this upgrade and the components we chose for our brake conversion. It also gives a pictorial overview of the installation process.

Trailer hydraulic disc brake and caliper installed on an RV wheel

The disc (or rotor) and caliper with red brake pads peeks out from inside our trailer wheel.

This is a long post. You can skip down to the different sections using the following links:

HOW TRAILER BRAKES WORK

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Electric drum trailer brakes and electric over hydraulic disc brakes function very differently.

To engage electric drum brakes in a trailer, when the driver depresses the brake pedal in the tow vehicle, an electrical signal is sent to the trailer’s brakes via a brake control unit in the truck. The brake control may be factory installed or it may be an external unit that is installed by the owner. The electrical signal engages an electromagnet on the trailer’s wheels that expands the brake shoes as the current gets stronger, creating friction on the wheel and slowing it down.

Brake Pedal -> Electrical Signal via Brake Control -> Trailer Brakes

To engage electric over hydraulic disc brakes on a trailer, when the driver depresses the brake pedal in the tow vehicle, an electrical signal is sent to a brake actuator unit in the trailer via the brake control unit in the truck. The brake actuator in the trailer then pumps hydraulic disc fluid through a line to the disc brake calipers on the trailer’s wheels. The build-up of fluid pressure actuates the brake calipers which, in turn, squeeze the brake pads against the disc, slowing the trailer down.

Brake Pedal -> Electrical Signal via Brake Control -> Brake Hydraulic Fluid Pumped by Brake Actuator -> Trailer Brakes

Drum brakes are an older technology. However, RV trailer manufacturers continue to install electric drum brakes to this day because it is far less expensive than installing electric over hydraulic disc brakes. The highest end full-time fifth wheel trailers are frequently offered with an option for electric over hydraulic disc brakes, but they are rarely provided as standard equipment.

Besides greatly increasing overall braking power, one of the biggest advantages of hydraulic brakes is that it is much easier to modulate the brakes for smoother stopping. In contrast, electric drum brakes on trailers can be very jerky, as the brakes are either ON or OFF. We often used to feel the trailer bump into the back of our truck as we stopped, hitting us with a jolt.

TRAILER ELECTRIC OVER HYDRAULIC DISC BRAKES versus CAR HYDRAULIC BRAKES

Cars are manufactured with hydraulic brakes, sometimes with disc brakes in the front and hydraulic drum brakes in the back. Many high end bicycles are even built with hydraulic disc brakes! Electric over hydraulic trailer disc brakes are slightly more complex than car hydraulic brakes, but they provide trailers with the same smooth stopping power that we enjoy in our cars.

The difference between the way hydraulic disc brakes on cars and electric over hydraulic disc brakes on trailers function is that there is no electrical signal involved in a car’s braking system. This is because the car is a single vehicle. No signal needs to be passed from one vehicle to another, as it does with a truck and trailer combo. The tricky part about a truck/trailer is that the brake pedal is in the front of the truck by the driver’s foot while the trailer’s brakes are way behind the driver at the back end of the trailer. Also, in a car, the hydraulic fluid is located under the hood in a master cylinder which performs the same function as the brake actuator that is located in the trailer.

Again, in a car, when the brake pedal is depressed, hydraulic fluid flows directly to the brakes to engage them. In a truck and trailer combo, an electrical signal has to be passed from the truck to the trailer to activate the hydraulic disc brakes in the trailer via the brake actuator.

ON THE ROAD COMPARISON OF TRAILER BRAKING SYSTEMS:
Electric Drum versus Electric Over Hydraulic Disc Brakes

Our fifth wheel trailer, a 36′ 2007 NuWa Hitchhiker II, came with factory installed electric drum brakes. We towed it, with that braking system, behind our 2007 Dodge RAM 3500 truck for the first six years we owned it, for a total of about 40,000 miles. When we upgraded to electric over hydraulic disk brakes, we were stunned by what a massive improvement in braking power and safety that simple upgrade provided!

We have now towed our trailer over 1,200 miles since the brake system upgrade, traveling on interstate freeways, maneuvering around tight gas stations and campgrounds, and driving in gnarly stop-and-go-traffic in slick, rainy weather. All we can say is:

“We should have done this a long time ago — probably on Day 1!”

The differences we experienced between the electric drum brakes and the electric over hydraulic disc brakes can be summed up as follows:

DRIVING AND STOPPING COMPARISON

Electric Drum Brakes Electric over Hydraulic Disc Brakes
The truck felt like it was stopping the trailer The truck and trailer stop together evenly without one stopping the other
Braking was either ON or OFF, resulting in a jerky motion Braking is proportional to your speed and is very smooth
Had to mess with the brake control every time we changed between highway and gas station speeds Haven’t touched the brake control since the upgrade was installed
As brakes age, braking power decreases As brakes age, braking power does not change

 

MAINTENANCE COMPARISON

Electric Drum Brakes Electric over Hydraulic Disc Brakes
Have to remove wheel and brake hub to inspect brake pads
  • Easy to inspect disc pads without removing the wheels to see if they are worn (use a mirror if they are hard to see)
  • Periodically have to adjust the drums Never have to adjust the discs
    Have to have drums turned OR replace the drums and backing plate with magnet, shoes, springs and cables Easy to replace brake pads with standard GM brake pads from an auto parts store if rotors are okay
    Removing trailer tires to grease the wheel brearings

    Mark removes the trailer wheels to grease the wheel bearings.

     

    DECIDING TO UPGRADE THE TRAILER BRAKING SYSTEM

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    We decided to do this brake system upgrade after Mark inspected the condition of the electric drum brakes that had been factory installed on our fifth wheel when we bought it new seven years ago. He was greasing the trailer’s wheel bearings, and while he had one of the wheels disassembled, he inspected the brake assemby inside.

    Greased wheelbearings on a trailer

    Mark used a Zerk gun to grease the trailer’s wheel bearings.

    He was dismayed to find that both the magnet and the braking surface were basically shot. He completed the wheel bearing lube job, but after he got the wheels mounted back on the trailer, we weighed our options for the brakes.

    Inside a trailer brake drum

    The inside of the trailer wheel and electromagnet at the bottom.

    Electromagnet inside an RV trailer brake drum

    Lots of wear on the electromagnet that controls the electric drum braking mechanism.

    As mentioned above, besides providing inferior braking power all together, one of the disadvantages of electric drum brakes is that, as the brakes age, the braking power gets progressively worse. Not only does the braking surface wear down but the electromagnet gets worn as well.

    In recent months, Mark had been noticing that the trailer brakes were not working as well as when the trailer was new, although he was shocked to see just what poor shape they were in when he disassembled the wheels!

    It is possible to have trailer brake drums turned. “Turning” involves putting the brake drums on a lathe and grinding the surface down to get rid of ridges and make it smooth. However, while a car’s drum brakes can be turned at an auto parts store, trailer brakes need to be taken to a machine shop. This is because they have to be turned not only on the braking surface that the brake pads ride on, but on the electromagnet surface as well. One of the disadvantages of turning the drums, however, is that it makes the braking surfaces thinner and weaker.

    When we began investigating the cost of having the drums turned, we found that it would not be that much less than the cost of replacing the brakes all together which would be somewhere in the neighborhood of $500.

    An alternative to turning the drums or replacing the brake assemblies would be to upgrade the trailer’s entire braking system to electric over hydraulic disc brakes. This is an expensive endeavor, on the order of $3,200, but the more we thought about our personal safety on the road, the more it seemed like it was a wise choice to do the brake conversion.

    THE COMPONENT PARTS OF AN ELECTRIC OVER HYDRAULIC DISC BRAKE SYSTEM

    There are three components involved in the installation of electric over hydraulic disc brakes:

    • Brake Control in the truck
    • Brake Actuator in the trailer
    • Hydraulic Disc Brakes on the trailer wheels

    In between these components there is both wiring and high pressure line:

    • The Brake Control must be wired into the truck (late model trucks have factory-installed brake controls).
    • The Brake Actuator must be wired into the 7-pin connector on the trailer that the truck plugs into.
    • High pressure lines must be installed between the Brake Actuator and the Disc Brake assembly on each wheel

    Our first job was to determine which components to install. Reading many reviews and talking at length with each manufacturer and visiting several booths at the Quartzsite Arizona RV Show, we chose:

    Kodiak Hydraulic Disc Brakes

    The heart of the electric over hydraulic disc brake system is the disc brake assembly itself, and Kodiak makes superior quality brakes.

    Kodiak has been making disc brake assemblies for over twenty years and is very highly regarded. Kodiak originated as a parts manufacturer for boat trailers, and their brakes are extremely popular in the boat trailer market.

    Kodiak dIsc brake rotor and caliper assembly for RV electric over hydraulic disc brakes

    Kodiak disc brake assembly
    Rotor and caliper installed on the axle.

    Since many boaters launch their boats in the ocean, Kodiak hydraulic disc brake assemblies are offered with dacromet coating and stainless steel options so they can withstand the continuous and highly corrosive drenching they get when boaters launch their boats on and off their trailers in salt water.

    Kodiak disc brakes are also very popular in the horse trailer industry, especially on the largest, heaviest horse trailers that carry multiple horses and have living quarters as well.

    To see the parts included in a Kodiak disc brake assembly, click here.

    Hydrastar Brake Actuator

    The brake actuator is the key middleman in the trailer braking system, and the Hydrastar Electric over Hydraulic Disc Brake Actuator from Cargo Towing Solutions has an excellent reputation as being extremely durable and rugged, even when mounted on the tongue of a travel trailer.

    The role this unit plays is vital, as it is the part of the system that receives the electrical signal coming from the brake control in the truck and, in turn, pumps the hydraulic fluid out to the disc brakes on the trailer’s wheels.

    Hydrastar electric over hydraulic disc brake actuator from Cargo Towing Solutions

    Hydrastar electric over hydraulic disc brake actuator.

    Like Kodiak, the the Hydrastar electric over hydraulic brake actuator is engineered for the salt water boat trailer market where water and corrosion are everyday challenges. The Hydrastar brake actuator is sealed extraordinarily well so it can be mounted on the tongue of a travel trailer. The whole circuit board is covered in epoxy and can function perfectly well when submerged under water. One of their most popular trade show demonstrations is to show the Hydrastar brake actuator working while suspended inside an aquarium full of water.

    Prodigy P3 Brake Control

    We have had an older generation Prodigy brake control in our truck since we purchased our first 27′ 2007 Fleetwood Lynx Travel Trailer, however, it does not work with electric over hydraulic disc brakes. We were delighted to find that there is a much better Prodigy brake control on the market now.

    Prodigy P3 Brake Controller

    Tekonsha Prodigy P3 Brake Control

    The Prodigy P3 is portable and has been designed for people who use many different tow vehicles to tow many different trailers. Not only can it be moved from truck to truck easily, it can memorize its programmed settings for different trailers. It can even be programmed for one trailer that has different characteristics at different times, for instance, a 7-horse trailer that may be loaded with 7 horses or may be empty.

    Best of all, we could swap out the old Prodigy for the new P3 easily because the new unit used the same wiring harness as the old one.

     

    INSTALLING ELECTRIC OVER HYDRAULIC DISC BRAKES ON A TRAILER

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    Mark was confident he could do the upgrade himself. However, he was not sure he wanted to tackle running the high pressure hydraulic lines. He did that kind of work when we installed the engine-driven ocean water desalination system on our sailboat, and it was challenging getting the lines cut and getting the fittings installed on the cut line. He decided he would prefer to have professionals install this system, and we did a search to find a company that has done hundreds of trailer brake system upgrades.

    Trailer brake upgrade at Zanetti Trailer Repair

    Our buggy gets set up in a repair bay at Zanetti Trailer.

    Zanetti Trailer Repair is located just west of Fort Worth, Texas, in the town of Weatherford, and they do this kind of brake conversion frequently. Considered a horse trailer guru, Pete Zanetti started the company in 1980, and it is still a family operated business.

    Texas doesn’t have the best winter weather, and when we arrived after driving through the remnants of a horrific ice storm, our trailer was covered with a thick layer of road grime, but our gleaming new parts were ready and waiting.

    Electric over hydraulic disc brake upgrade parts

    The disc brakes, brake actuator and brake control are ready to be installed on our trailer.

    A team of three mechanics jumped on the job. To our amazement, within three hours they had completed the entire installation!

    Below is a summary of the steps they took to do the brake system upgrade.

    First, after jacking up the trailer, the wheels were removed.

    Removing wheels from a 5th wheel trailer

    Our buggy’s wheels are removed once again.

    Wheels removed from fifth wheel trailer RV

    Right down to the axles and spindles.

    Then the backing plates for the disc brakes were installed on the axles.

    Disc brake backing plate on a trailer axle and spindle

    The disc brake backing plate is mounted on the axle.

    On a table to the side, the four sets of brake assemblies and bearings were laid out, ready to be greased and put together.

    Hydraulic disc brake components- calipers, rotors and bearings

    The four rotors and calipers will be put together in assembly-line fashion.

    Here’s a closeup of the brake calipers with the red brake pads inside. The red brake pads will need to be replaced when the indented brake surface material wears away.

    Kodiak disc brake caliper with brake shoes

    The Kodiak disc brake caliper.

    Kodiak trailer disc brake caliper with brake shoes

    The brake pads are red, and when worn down to the indent, they will need replacing.

    The wheel bearings and seals were laid out, ready to be inserted in the brake rotor.

    Wheel bearings for Kodiak trailer disc brakes

    New wheel bearings ready to be lubed up and installed.

    Mark had just finished greasing the old wheel bearings on our trailer using a zerk gun. What a surprise it was to see a huge trash barrel filled with wheel bearing grease!

    Barrel of wheel bearing grease

    A Barrel O’ Grease — wow!
    They used an extremely sticky grease.

    The rotors were greased and then the new bearings were pressed in.

    Greasing the rotor on RV hydraulic disc brakes

    Greasing the inside of the rotor.

    Pressing the wheel bearings into the rotor on trailer disc brakes

    Pressing grease into a wheel bearing.

    Then the brake rotors were installed on the axles, and the brake calipers were installed on the rotors.

    Trailer disc brake rotors installed

    The brake rotors are installed on the axles. A brake caliper waits its turn on the ground.

    Kodiak dIsc brake rotor and caliper assembly for RV electric over hydraulic disc brakes

    Kodiak disc brake assembly with rotor and caliper mounted on the trailer’s axle.

    Outside (in the rain!) the old brake hubs had been discarded.

    Old trailer electric drum brakes in the trash heap

    We won’t need these any more!

    Meanwhile, the installers got busy installing the Hydrastar brake actuator in the trailer and wiring it to the fifth wheel pin box. To test the installation, they used a special electronic unit to simulate a person pressing on the brake pedal in the truck.

    Installing the Hydrastar brake actuator on a fifth wheel trailer

    Wiring the Hydrastar brake actuator into the
    fifth wheel pin box.

    Then they unrolled and straightened the stainless steel brake line tubing…

    Measuring and cutting electrical wire for trailer disc brake actuator installation

    Unrolling and straightening the stainless steel brake line tubing.

    … and ran the electrical wires from the pin box into the fifth wheel basement

    Wiring in electrical cable for disc brake actuator in a 5th wheel trailer RV

    Feeding the electrical wire through to the fifth wheel basement.

    The Hydrastar brake actuator unit found a home just inside one of the basement side access doors.

    Hydrastar disc brake actuator from Cargo Towing Solutions

    Hydrastar disc brake actuator installed in the fifth wheel basement.

    Hydrastar hydraulic trailer disc brake actuator from Cargo Towing Solutions

    The Hydrastar disc brake actuator is close to a side hatch for easy access.

    On the underside of the trailer and along the trailer axles, they did a superior job of dressing the hydraulic brake line and connections.

    Hydraulic brake line dressed on bottom of RV

    Looking up at the bottom of the trailer, the hydraulic lines run underneath the trailer, neatly dressed.

    And then they bled the brake lines.

    Bleeding the hydraulic brakes on an RV

    Bleeding the hydraulic brakes. A special box simulated a person depressing the brake pedal in the truck.

    Then it was time to put the Prodigy P3 Brake Control into the truck. This is a portable unit that comes with a carrying pouch. We have only one truck, so we won’t be carrying the brake control from one truck to another. Mark later found the little pouch was perfect for his pocket camera!

    Prodigy P3 Brake Control from Tekonsha

    The Prodigy P3 Brake Control is a nifty portable unit that can be moved
    from one tow vehicle to another.

    The brake control is on the lower right side of the dashboard under the steering wheel.

    Prodigy P3 Brake Control installed on a Dodge RAM 3500_

    Prodigy P3 Brake Control mounted below our Dodge RAM 3500 dashboard

    We were astonished that all this had taken just under three hours, and the installers were almost finished. Wrapping up the job, the wheels were mounted back on the trailer and the trailer was taken off the jacks.

    Replacing the wheels on a fifth wheel trailer

    The wheels get mounted back on the trailer axles.

    The new disc brakes looked very spiffy peeking through our dirty wheels!

    Dirty Wheels and new electric over hydraulic trailer disc brakes

    Oh gosh — sure wish we’d cleaned those wheels before this installation!
    But the brand new disc and caliper look great in there…

    It was time to hitch up the trailer and hit the road with our new brakes. I loved the little painted stone outside the office door.

    Zanetti Trailer - We'll Fix Your Wagon

    Zanetti Trailer’s motto is “We’ll Fix Your Wagon” !!

     

    SUMMARY

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    Mark was blown away when we got the trailer out on the highway. On the Prodigy P3 Brake Control, he experimented with a few settings and settled on a boost of “B2” and 8.5 volts. As we eased onto the highway, he commented, “It feels like I’m driving a car!”

    During the next three weeks we made our way from central Texas to the Florida coast, driving in all kinds of conditions, from remote back roads, to many miles on the I-10 Interstate freeway. We sat for hours in massive stop-and-go traffic jams around big cities, and Mark coped with tricky driving situations on small downtown city roads with lots of stop lights.

    In the past, if a traffic light turned yellow at the wrong moment as we approached, we just had to keep going and cross our fingers that it wouldn’t turn red while we were crossing the intersection, because we just couldn’t stop the trailer in such a short distance. No more!! On many occasions, as we came to an intersection, the light turned yellow on our approach, and Mark was able to stop the truck and trailer in time in a nicely controlled manner.

    In Fort Worth, TX, and again around Baton Rouge, LA, we found ourselves in amazingly congested traffic. Mark was able to relax in the heat of the battle, completely confident that he could stop the trailer in a very short distance if need be.

    Fifth wheel trailer RV in Florida at sunset

    Sometimes the best improvements are not something you can see on the surface!

    When we got into Sarasota, Florida, we came across some astonishingly aggressive drivers. One driver cut us off with just an inch to spare, instantly coming to a complete stop directly in front of us. It was a heart stopping moment that all RVers dread. Mark slammed on the brakes with a force I have never seen him use, either in a car or in our truck pulling our home.

    All the tires of the truck and trailer squealed as we came to a shockingly abrupt stop, leaving lots of rubber on the road behind us. We were both stunned that the trailer stopped in such a short distance. There is no doubt that if we had had our old electric drum brakes, we would have rear-ended the car in front of us and had a really bad — and possibly life threatening — accident.

    Believe me, the irony that we had just replaced our brakes, and had jokingly said we needed to test just how good they were, was not lost on us. But we never would have lurched our house like that just to see if the brakes worked!!

    This brake conversion is an upgrade that Mark dreamed of doing for ages, ever since our RVing mentors Bob and Donna Lea had told us about how differently their electric over hydraulic disc brakes performed on their 33′ fifth wheel compared to the electric drum brakes they’d had on other trailers.

    In the end, it was totally painless and very easy to do, and looking back, we realize we should have just bitten the bullet the first year we owned our trailer and gotten it done right away.

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    11 thoughts on “Trailer Disc Brake Conversion – Electric Over Hydraulic Disc Brakes – WOW!

    1. Our new Mobile Suite came with electric over hydraulic brakes and I noticed the difference right away in the stopping power over our old trailer with electric brakes. It certainly is well worth the investment. One more year until we rite and can’t wait to hit the road in the fall of 2016. Hope someday to cross paths, but until then will continue to follow your postings. Safe travels and Happy Easter.

      • How nice to have electric over hydraulic disc brakes come with your new fifth wheel, Bill — lucky you! 2016 will be here before you know it, and you’ll be out enjoying your new freedom. Have fun!!

        • Jack Janssens sr I had our brakes replaced with mor/ryde brakes which is the same, electric over hydro in 2008 on our 03 carriage cameo and never felt safer. The only way to go, should be standard for safety.

    2. I installed a Tekonsha P3 brake controller when we bought our travel trailer. We used it over 25,000 miles in 2.5 years and never had any problems with it. It was very simple to install and program and can be used in any vehicle by changing to the appropriate pigtail. As you said, it is adjustable for any trailer load and had many more features than we were able to use. We only sold it with our travel trailer because our new Ram 2500 came with a factory-installed brake controller.

    3. Thank goodness I’m reading this before buying my rig! Now I’ll include the brake conversion in the budget and custom work timeline for time of purchase. I already have a world class mechanic who can fix anything, so I’m sure he can do this, too. Being a trained CDL driver, former pizza driver and survivor of six not-at-fault accidents in a ten year period and reporter of two pileups involving trucks sent flying by vehicles with poor brakes, I firmly believe you should ALWAYS put your best foot forward where brakes are concerned. Had I known you were going I-10, as a Bayou State native, I would have strongly recommended another route. B.R. remains in a constant state of congestion, which causes people to get stuck riding out hurricanes. I especially recommend avoiding the area Aug-Sept, when hurricanes are frequent and Nov, when they can be worst, Rita and Katrina being the rare exception. Well done, Mark and Emily! ^5

      • You’re so right, Belinda, it’s really wise to put your best foot forward where brakes are concerned!! Also, I’m glad to know there’s a smoother way to get to FL from TX, but we managed to gut it out on I-10 this time, and it was definitely a great test of the new brakes. Enjoy your search for a rig — with any luck it will have disc brakes already!!

    4. This is really interesting for me because I don;t know the first thing about breaks. It is fascinating to me that there is magnetic that go on in the brake system. This actually makes me want to disassemble my brakes to figure it our first hand.

    5. That brake control unit looks really cool! I like that it’s easy to switch between trucks and remembers settings for various things it tows. This would be really helpful for families like my aunt and uncle who have three trucks, a few different trailers, and a mobile home.

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