Trailer Components — Trailer Safety Week

Whether or not your trailer requires brakes is a matter of both federal and state law. Federal law, in short, requires brakes on all axles of the trailer when it is over 3,000 lbs. GVWR and is used for commercial purposes. State law dictates brake requirements beyond what is outlined by federal law, including non-commercial use.

Federal Brake Law:

Federal Law requires brakes be placed on axles of trailers used for a commercial purpose (with notable exceptions found below). However, understanding what a commercial use is, can be confusing.

Per 49 C.F.R. § 390.5, a commercial motor vehicle means, as pertinent to trailers, “any …towed motor vehicle used on a highway in interstate commerce to transport … property when the vehicle -

1. Has a gross vehicle weight rating or gross combination weight rating, or gross vehicle weight or gross combination weight, of 4,536 kg (10,001 pounds) or more, whichever is greater; or

2. Is used in transporting material found by the Secretary of Transportation to be hazardous under 49 U.S.C. 5103 and transported in a quantity requiring placarding under regulations prescribed by the Secretary under 49 CFR, subtitle B, chapter I, subchapter C.”

Of particular relevance for trailers in the definition is the requirement that the GVWR or GCWR be 10,001 lbs. or more. This means that in order to come within the definition of a commercial motor vehicle subject to the regulations of FMCSA, either the trailer by itself or the combined GVWR of the trailer and tow vehicle combination must be 10,001 lbs. or more.

Examples of Commercial Purposes:

FMCSA does not provide an express definition of “commercial” or commercial use; however, examples of trailers that could be considered for commercial use are those used for compensation or earning profits, including, but not limited to, uses such as transporting freight, operating landscaping and construction businesses, and populating city and county trailer fleets. Another common, but often overlooked potentially commercial use is transporting show horses or livestock when prize money, a form of compensation, is at stake.

Any commercial trailer meeting the above definition must comply with 49 C.F.R. § 393.42, requiring brakes on all wheels as specified below.

Language and Exceptions:

49 C.F.R. § 393.42 states:

A. “Every commercial motor vehicle shall be equipped with brakes acting on all wheels. This requirement also applies to certain motor vehicles being towed in a driveaway-towaway operation, as follows:

1. Any motor vehicle towed by means of a tow-bar when another motor vehicle is full-mounted on the towed vehicle; and

2. Any saddlemount configuration with a fullmount.”

B. “Exception.

1. Trucks or truck tractors having three or more axles and manufactured before July 25, 1980, are not required to have brakes on the front wheels. However, these vehicles must meet the requirements of § 393.52.

2. Motor vehicles being towed in a driveaway-towaway operation (including the last truck of triple saddle-mount combinations (see § 393.71(a)(3)) are not required to have operative brakes provided the combination of vehicles meets the requirements of § 393.52.

3. Any semitrailer or pole trailer (laden or unladen) with a gross weight of 1,361 kg (3,000 pounds) or less which is subject to this part is not required to be equipped with brakes if the axle weight of the towed vehicle does not exceed 40 percent of the sum of the axle weights of the towing vehicle.

4. Any full trailer or four-wheel pole trailer (laden or unladen) with a gross weight of 1,361 kg (3,000 pounds) or less which is subject to this part is not required to be equipped with brakes if the sum of the axle weights of the towed vehicle does not exceed 40 percent of the sum of the axle weights of the towing vehicle.

5. Brakes are not required on the steering axle of a three-axle dolly which is steered by a co-driver.

6. Loaded housemoving dollies, specialized trailers and dollies used to transport industrial furnaces, reactors, and similar motor vehicles are not required to be equipped with brakes, provided the speed at which the combination of vehicles will be operated does not exceed 32 km/hour (20 mph) and brakes on the combination of vehicles are capable of stopping the combination within 12.2 meters (40 feet) from the speed at which the vehicle is being operated or 32 km/hour (20 mph), whichever is less.”

If 49 C.F.R. § 393.42 requires brakes on commercial-use trailers, then 49 C.F.R. § 393.40 also requires the brakes to be “adequate to stop and hold the vehicle or combination of motor vehicles” and the vehicle to “meet the applicable service, parking, and emergency brake system requirements provided in [§ 393.40].”

State Brake Laws:

Brake laws vary greatly by state. To find an up-to-date list of laws by state visit https://drivinglaws.aaa.com/tag/trailer-brakes/. It is important to note that if you purchase a trailer from another state in which the trailer will be registered and/or primarily used, you will want to ensure the trailer meets the appropriate laws of the state in which it will be registered or primarily used.

Brake Types:

Trailer brakes can be hydraulic (surge), electric, or both. All trailer brake systems must incorporate a trailer breakaway brake system that activates when the brakes detach. Just as your brakes require regular maintenance, so too does your breakaway system.

Electric Brakes:

Electric brake systems require the use of an electric brake controller in the cab of the tow vehicle. In short, when the tow vehicle brake pedal is engaged, the electric brake controller engages the trailer brakes.

It is important to note that electric brake controllers provide a modulation function that varies the current to the electric brakes in proportion to the deceleration of the tow vehicle. This is important because the braking of the tow vehicle and the trailer needs to be synchronized to ensure proper distribution.  Synchronization is accomplished by adjusting the “gain” on the tow vehicle controller. With the tow vehicle hooked up to the trailer, make several hard stops on dry pavement. If the trailer’s brakes skid or are too sensitive, decrease the gain on the brake controller. If they do not skid, slightly increase the gain setting until they have reached a desired braking point. This adjustment will need to be made with each varied trailer load. A heavier trailer will require more gain than a lighter trailer. A lighter trailer with brakes synchronized to a fully loaded trailer, will probably lock-up easily with only minimally commanded deceleration.

Electric brakes are very efficient, reliable and can be controlled by the operator from inside the tow vehicle. The draw back is the tow vehicle must have a “brake controller” installed. If the tow vehicle is not equipped with a controller unit, the vehicle cannot actuate the brakes and should not be used to tow a trailer with electric brakes.

Hydraulic Brakes:

Hydraulic or surge brakes function through the use of a special coupler on the trailer that compresses a piston in a hydraulic cylinder when the tow vehicle decelerates and the trailer surges forward. When this occurs, brake fluid is then forced to the brake assembly on each wheel. Because hydraulic brakes are entirely self-contained, any tow vehicle can use a trailer with a hydraulic brake assembly.

It is important to note that some states and the Federal Motor Carriers Safety Administration have placed limitations on the use of surge brakes for commercial vehicles. These limitations surround the GVWR of the trailer as it compares to the GVWR of the tow vehicle.

Electric-Over-Hydraulic Brakes:

Electric-over-hydraulic brakes are a hybrid system that actuates when the brakes of the tow vehicle are engaged and the trailer surges forward. The key difference is the actuator in this combination is electric, providing little to no lag time due to an instant application. This system is used most often on trailers like large horse trailers and boat trailers. It is important to note that the system cannot be submerged (though they are built to withstand rain) so users will need to be careful if using these for hauling boats.

Electrical Breakaway Brake System Batteries

Per Part 393.43 (d) of the Federal Motor Carrier Safety Regulations: Breakaway braking requirements for trailers states: “Every trailer required to be equipped with brakes shall have brakes which apply automatically and immediately upon breakaway from the towing vehicle. The brakes must remain in the applied position for at least 15 minutes.” The last statement is found in most state’s trailering statutes. Therefore, regardless of the application (i.e. commercial or personal use), the breakaway battery should be able to keep the electric brakes applied for 15 minutes.