This article will cover the different types of trailers for semi-trucks. So, what is a trailer? What are the different types of trailers for semi-trucks? A semi-trailer is a trailer without a front axle. In the United States, the term is also used to refer to the combination of a truck and a trailer also called a tractor-trailer.
A large proportion of a semi-trailer’s weight is supported by a tractor unit, or a detachable front-axle assembly known as a dolly, or the tail of another trailer. A trailer is normally equipped with landing gear (legs which can be lowered) to support it when it is uncoupled.
Many trailers have wheels that are capable of being totally dismounted and are also relocatable (repositionable) to better distribute the load to bearing wheel weight factors Semi-trailers are more popular for transport than full trailers, which have both front and rear axles. Ease of backing is cited as one of the semi’s best advantages.
Semi-trailers with two trailer units are called tandem tractor-trailers tandem rigs or doubles. Other terms used are “B-train” or (when there are three or more trailers) “road train”. A double-trailer combination is possible with the use of a dolly, or “converter dolly”, essentially one to three additional axles placed under the front of a second semi-trailer.
The first semi-trailer is connected to the power unit using the tractor’s fifth wheel coupling while the converter dolly, already attached to the second semi-trailer, is connected to the first semi-trailer with a drawbar. Read below for a list of the different types of trailers for semi-trucks.
Types of Trailers
Flatbed trailers are the most popular and common of the semi-trailer used today. The length is either 48 feet or 53 feet, and the width of 96 or 102 inches. Including rub rails and stake pockets on the sides, which are generally placed every 2 feet. Some older trailers are only 45 feet or shorter if used in sets of doubles or triples, often used to haul hay.
Several lengths and combination setups can only be legally driven on turnpike/toll roads which are far too long for most roadways. The body and frame can be one of 3 general designs: the heaviest and sturdiest is all steel, usually with wood planks.
The ever-popular combo with a steel frame and aluminum bed. These types often have a wood portion for nailing down dunnage boards, and aluminum. Which is the lightest allowing for more cargo to be legally carried without overweight permits.
Incredibly light and very expensive to purchase, all-aluminum trailers are very slippery when wet. They flex more and are easily damaged. They also have a natural upwards bend so that when loaded they straighten out to be flatter rather than sag in the middle under a load.
A lowboy is a semi-trailer with two drops in deck height: one right after the gooseneck and one right before the wheels. This allows the deck to be extremely low compared with other trailers. It offers the ability to carry legal loads up to 12 ft (3.66 m) tall, which other trailers cannot. Lowboys are used to haul heavy equipment such as bulldozers, industrial equipment, etc.
Lowboys are designed to carry massive weights. 2-axle lowboy trailers have a maximum weight of 40,000 pounds. Lowboys can go up to 80,000 depending on the number of axles used.
Lowboy trailers may require additional permits to operate. State or municipal regulations should be strictly followed.
A refrigerated trailer is also known as a reefer trailer. Generally used for transporting chilled or frozen products. The temperature inside this trailer can be controlled whatever the outside weather is.
Refrigerated trailers are basically dry van trailers that have a cooling system and are insulated to keep the enclosed goods fresh. This type of semi-trailer is mainly used for frozen food and produce. Sometimes pharmaceuticals are shipped via reefer trailers. The maximum weight for refrigerated trailers is the same as dry vans, but they have a maximum legal width of 8.2 feet and a maximum legal height of 8 feet.
Reefer trailers can handle a max weight of up to 45,000 pounds. Maximum refrigerated trailer length between 48 feet to 53 feet.
Conestoga trailers are made by Aero Industries. Design and features an innovative sliding tarp system that covers your valuable cargo without damaging the items underneath. This protects the finish or moving parts of the goods or equipment. By sliding the tarp over and around the goods or equipment, makes it unnecessary to move the goods in and out which limits the odds of scratching or damaging your freight.
Conestoga trailers are typically used sophisticated machinery or large items that need to stay in excellent condition.
The roll-tops usually made of heavy-duty plastic, rubber, or canvas. They have a length that ranges from 48 to 53 feet a maximum legal width of 8.2 feet and a maximum height of 8 feet. Maximum weight capacity of up to 45,000 pounds.
Step Deck Trailer
Step-deck semi-trailers are very similar to flatbed trailers with the only difference being the maximum fright height has to be 10 feet or less. Step decks we’re designed to carry goods that flatbed trailers could not. Mostly due to the height restrictions.
Also known as a step-deck or drop-deck trailer. The maximum legal dimensions are length 48 feet to 53 feet. Maximum step deck trailer width of 8.5 feet, and max legal freight height up to 10 feet. Step-deck can hold a maximum weight of 48,000 pounds.
Dry Van Trailer
A dry van is basically an enclosed trailer. Dry van trailers are the most common freight containers. These trailers are fully closed and sealed. Therefore, freight is protected from any external influence.
Dry vans don’t have temperature control, so you can only use them for moving non-perishable goods. Dry vans are weatherproof and keep the good dry from the elements. Used primarily for transporting hard and soft goods like some food, clothing, and other merchandise that need to be protected but not temperature sensitive.
Dry van maximum freight weight is 42,000 lbs to 45,000 lbs. Maximum dry van length 48’ to 53’, max-width of 8.2 feet, and a maximum height of 8 feet.
Power Only Trailer
Power-only trailers are used to tow other trailers. The requirements and legalities differ from state to state.
Power-only trailers have an adjustable fifth wheel that helps the truck fit the dimensions and specifications of your trailering on the weight loads and standard size load versus oversize loads, standard axle units, as well as four-axle units, available to suit your trucking needs.
Extendable Double Drop Trailer
Extended double drop trailers are primarily used to carry and haul freight that has an excessive length that standard double drop trailers can handle. Typically have 2 to 3 axles trailers and their length ranges from 29 to 65 feet. With a load height of 11.6 feet and a width of 8.5 feet. And mac freight weight of 40,000 lbs.
Like the name says double drop, the lower deck height lets you load products that are taller than 10′. It has a longer section in the middle called the “well”. The “well” usually ranges from 25-29′.
Common things to carry on an extendable double drop trailer are heavy equipment and construction equipment.
Stretch Double Drop Trailer
This trailer generally transports oversized equipment. The lower deck allows for loads that can be as tall as 10 feet. The well or the lower section has a length of 25 to 29 feet.
The stretch double drop maximum weight capacity is 45,000 lbs. The legal max length for the main deck is 29 to 65 feet and the max width of 8.5 feet. The legal freight height is 11.6 feet.
Stretch Single Drop Deck Trailer
This trailer is specifically designed to transport and haul extremely long freight. It provides support and prevents overhang from extra-long equipment.
The stretch single drop maximum weight capacity is 45,000 lbs. The legal max length for the main deck is 35 to 63 feet and the max width of 8.5 feet. The legal freight height is 10 feet.
Removable Gooseneck Trailer (RNG)
These trailers are perfect for hauling both tall and heavy loads and equipment. Designed to carry up to 150,000 pounds depending on the number of axles the trailer has.
Removable gooseneck trailers can have up to 20 axles. The maximum legal length is 29 feet. RGN max weight is from 42,000 to 150,000 lbs. Max length of 29’ and a width of 8.5 feet. Legal max height of 11.6 feet.
Stretch Removable Gooseneck Trailer (RNG)
The stretch rng trailer is similar to the removable gooseneck trailer but the stretch version has a maximum length of 65 feet. With a heavier load, more axles will be required, but the absolute minimum is three axles.
Design to transport massive loads and equipment. The maximum legal length is 29 to 65 feet. With the max weight from 42,000 to 150,000 lbs. Max width of 8.5 feet. Legal max height of 11.6 feet.
Sidekit trailers are most often equipped with wood side paneling and used to carry loads that aren’t packed, like dirt, gravel, and other materials that don’t need to be packaged.
Their max height is 8.6 feet, and their maximum width is 8.2 feet. Basically flatbed trailers with a 4-foot attached to the side of the trailer. Their maximum load weight of 45,000 lbs.
Specialty trailers are designed specifically for a specific type of product or hazardous materials to be hauled. They’re used for hauling fuel and other liquids. Specialty trailers have a lot of regulations.
Specialty trailers can hold up to 200,000 pounds. Other dimensions depend on regulations imposed by the state(s)
Multi-car trailers are used to transport cars and trucks. They can carry anywhere from two to eight vehicles. When you need to haul several vehicles you’ll use a double-decker trailer. The height can not exceed 11.6 feet because of overpass heights.
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