youtubeIn a previous "Ask Dave" article, we looked at RV tires and motorhome brakes. While motorhome braking systems are similar to what is used in the automotive and trucking industries, the braking system on towable RVs like travel trailers, tent trailers and fifth wheels is totally different. Take a break and learn more...

The following is an overview of the typical braking system found on the majority of towable RVs and what you should know about safety and service.

º How they work: When you apply your brakes in the tow vehicle or manually engage the brake control in the tow vehicle, the brake control sends an appropriate amount of voltage to an electro-magnet contained within the hub / drum assembly located behind and bolted to each wheel of the RV. When energized, the magnet, which is mounted on the end of the actuating arm, grips (sticks) to the steel armature surface of the spinning brake drum. The magnet trying to attach itself to the spinning drum pulls on the actuating arm which in turn pushes out (expands)  the brake shoes to make contact with the inside of the drum, thus slowing the trailer. Here is a video demonstrating the process.

º Breakaway Switch: On the tongue of a trailer or near the king pin of a fifth wheel, you will find a small box with two wires coming out of it and a cable attached to a pin inserted into the box. This is the breakaway switch which will engage the brakes of the RV in the event it becomes separated from the tow vehicle. Here’s how it functions – When the RV is hooked up to the tow vehicle, the looped end of the breakaway switch cable is securely attached to the tow vehicle. If the RV were to become detached from the tow vehicle, the pin will be pulled out of the breakaway switch allowing full voltage to flow out of the RVs house battery to the magnets in the brake assemblies fully engaging the brakes. This is designed solely as a safety device to stop the RV in the event it becomes detached from the tow vehicle while traveling down the road. It is not designed for use as a parking brake. If the breakaway switch is left engaged for more than a few minutes, you risk overheating the brake magnets and / or depleting the RVs 12-volt house battery. Once the house battery is depleted, the RV brakes will release allowing the RV to freely roll if not properly chocked. It is highly recommended to check the operation of your breakaway switch once a year by pulling the pin and attempting to drive forward.


Breakaway Switch

º How long will my brakes last? It depends on the amount of use / disuse and age. Just like automotive style brakes, the amount of use determines how quickly the brake linings become worn away by how often they are applied. In addition to the brake linings, the face of the magnet is being worn away each time the magnet is energized and engages against the armature of the brake drum. Note: If the linings or magnets are allowed to wear down too far the brake ­drum can be damaged. To extend the life of your brakes, downshift into lower gears when descending steep grades allowing the tow vehicle engine to do most of the braking. Just like we reviewed previously with RV tires, lack of use doesn’t mean your brakes are fine either as just sitting can cause parts to fail. Two potential failures are due to age and lack of use include the linings separating from the brake shoe (bonding agent fails) or moving parts, like the actuating arm, becoming frozen (corroded) in place.

º How will I know my brakes need servicing? Unlike automotive brake systems there is no wear bar (aka squeaker) to emit an audio signal alerting you that brake linings or magnets need replacing soon.  Obvious signs you need to have brakes serviced are; they fail to engage when the brake control is energized or unusual noises coming from the drum assembly when in motion / braking. It is good idea to have your brakes (bearings too) inspected every year to assure they are properly operating and adjusted. Even if you have a newer towable RV with self lubricating wheel bearings and self adjusting brakes you should still remove the hubs/drums once a year for inspection of both the brakes and bearings as a failed bearing / grease seal can allow grease onto the drum negating most of the braking power.

º Adjustment: If the unit is not equipped with self adjusting brakes it will have to be done manually. Here is a link to an instructional video on how to do so. Clues that it is time for adjustment include; erratic braking such as coming on really hard, brakes not easily releasing after stopping or braking feels weak (ie. – RV “pushes” the tow vehicle when braking).


Properly Working Break System is Imperative When Descending a Road Like This

Hopefully this beginner’s primer into towable RV brakes provides you with the information you need to understand how the brakes work and when they need service.

Dave Helgeson
Author: Dave HelgesonEmail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Lifetime RVer and former RV dealer, Dave Helgeson, answers readers' questions. To submit a question for Dave, send an email to This email address is being protected from spambots. You need JavaScript enabled to view it. or send us a message through our Facebook page at https://www.facebook.com/northwestrving.

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