Semi-trucks have a variety of trailer options to choose from. Depending on the type of cargo they need to transport and the size of their payload, this will determine the size and style of the trailer they will need for the specific job.
Although there are several styles of trailers to use for hauling, they all have the same basic components. A typical semi-trailer consists of:
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- Kingpin: which will slide into the fifth wheel of the tractor
- Bed: either covered or uncovered
- Axles: a minimum of two axles, with two tires on each side
- Air Brake System (ABS): this brake system includes both the trailer brake circuit and the parking brake circuit
- Electrical: electrical hookups and wiring for rear lighting and signaling
- Suspension: connects wheels, axles & brakes to the body of the trailer while also absorbing the physical blows of hauling freight
On top of the semi-trailers basic components, they can be customized with specific add-ons which are mainly for the purpose of improved aerodynamics. A more aerodynamic trailer significantly improves fuel economy by redirecting airflow to reduce drag. There are three main areas which cause drag:
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- Between the cab and trailer
- Panels have been engineered to extend off each side of the trailer and jut into that space, reducing the amount of trapped air inside.
- Underbelly of the trailer
- Side skirts can be placed along the side of the trailer, in front of the rear axles, forcing the air to travel up the side of the trailer instead of underneath.
- Rear of the trailer
- Trailer tails can be attached to the vertical sides of the trailer back. These allow the air to flow straight off the trailer instead of being pulled behind it, this alone can improve fuel efficiency up to 6%.
- Between the cab and trailer
Styles of Semi-Trailers
Whether you’re driving a day cab or a sleeper cab, you will be hauling a certain type of trailer in order to complete your route. For any type of freight, there is a specific style of semi-trailer suitable for the hauling task at hand. They can be broken down into five different categories.
- Flatbed Trailer
- Dry Vans (Enclosed Trailers)
- Specialty Trailers
- Tank Trailers
- Dump Trailers
Style 1: Flatbed Trailers
Flatbed trailers are the most extensive and versatile category which has many kinds of trailers to fit the needs of specific freight. They are used in almost every area of the United States as they’re primarily utilized for shipping construction materials and various equipment. Here are the 4 variations of the flatbed trailer:
1. Flatbed & extendable flatbed
- This is an open bed trailer that sits at a consistent height. A two-axle flatbed has a GVWR maximum weight of 80,000 pounds and length of 48’. A three-axle flatbed has a GVWR maximum weight of 90,000 pounds and length of 53’. An extendable flatbed can extend anywhere from 48’ – 80’. This is used for larger cargo that cannot be shipped via a standard flatbed.
2. Lowboy
- These trailers sit low to the ground which allows them to carry very tall freight. They can carry up to 95,000 pounds depending on the number of axles used and have a 24’- 29’ long bed. This type of trailer is used for large construction equipment, infrastructure piping, farm equipment and oversized items that cannot fit on a standard flatbed.
3. Drop
- This kind of trailer combines two deck heights in one trailer. There are 3 types of drop trailers:
- Single drop – this refers to a trailer that has two deck heights. A standard flatbed height then drops to a lowboy height. It has the same length and weight restrictions as a standard flatbed.
- Single drop stretch – has the same features of a single drop trailer but can extend anywhere from 48’ – 63’. The maximum weight is 80,000 pounds GVWR.
- Double drop stretch – this is a trailer that has two deck heights but begins at a standard flatbed height, then drops to a lowboy height, and back to a flatbed height, effectively forming a well in the middle of the trailer. The maximum weight is 90,000 pounds GVWR and can come any length between 29’- 65’.
4. Removable Gooseneck (RGN) & Stretch RGN
- These trailers are similar to a lowboy but the gooseneck, the component which attaches the trailer to the tractor, can be removed and the front end of the bed can drop down to create a ramp. This makes it perfect for carrying excessively long and tall freight. They have a minimum of three axles and can have up to 20 axles and carry up to 150,000 pounds, with a length of 29’. A stretch RGN can be up to 65’ in length.
Style 2: Dry Vans (Enclosed Trailers)
Dry Vans are some of the most commonly used trailers in the United States. They are fully enclosed, which protects the contents from weather and theft. These trailers range from 28″-53″ in length. They haul anything from building materials, household goods, or even consumables. An interesting fact is that two-thirds of all trailers on the road are dry vans. Here are a few of the types of dry van trailers:
1. Reefer Trailer or Refrigerator Trailer
- This type of trailer features a compressor and full insulation so it’s able to transport cold or frozen products. They’re oftentimes insulated and have a refrigeration unit mounted on the front. These trailers carry various products, such as food, make-up, paint, pharmaceuticals and many other products, in a range of -22 to 80 degrees Fahrenheit.
2. Conestoga Trailer
- A Conestoga trailer has the benefits of a flatbed, where the freight can be loaded onto the bed from any side and in any configuration, but it has a rolling tarp-on-frame system that can fully enclose the cargo, giving it the same protection as a dry van.
3. Side Kit Trailer
- The side kit trailer’s side panels are made of fiberglass or plywood, with a tarp that covers the top of the trailer. These are used for carrying loose materials such as coal, grain and gravel.
Style 3: Specialty Trailers
Specialty trailers provide options for transporting specific materials. They can carry over 200,000 pounds depending on the specific use. Of the dozens of specialty trailers there are four common types:
1. Hazardous Material Transport
- These trailers are cylindrical in shape and are used to ship petrol, chemicals, and other hazardous materials.
2. Food Service
- These trailers are outfitted with mobile kitchens that can be used for conferences, festivals, or temporary kitchens while brick and mortar renovations are completed
3. Event Marketing
- These can be used for advertisements and displaying products to a wider customer base
4. Medical
- These trailers carry medical supplies and resources to onsite staff and are often outfitted for mobile clinic operations, such as a blood bank
Style 4: Tank Trailers
1. Fuel Tanks
1. Fuel Tanks- Fuel tanks do exactly what you would expect them to: carry petroleum diesel & oils across the greater United States area
2. Pneumatic Tanks
- Pneumatic tanks are unique in that they haul plastic pellets, flour, cement and other dry products that are shipped in bulk
3. Specialized Tanks
- These kinds of tanks haul compressed gas, propane and other specialized chemical transport
Style 5: Dump Trailers
These types of trailers you may not see every day, but they’re very popular near work zones and construction sites. Those hauling dump trailers use this style to haul aggregate and materials to and from work sites and need to dump out their contents.
High-Quality Trailers At North American Trailer
If you need to purchase a trailer, our dedicated sales team at North American Trailer is here to help during the buying process. Regardless of the type of trailer, regular maintenance and service are essential to keep your trailer on the road. If you’re in need of parts or trailer service in the greater Twin Cities, MN area, you can trust the team at North American Trailer to take care of you.
With over 35 years of experience and four locations across 2 states, you can count on us for all your trailer needs.