What is an 18-Wheeler? (with pictures)

An 18-wheeler is a combination of a semi truck/tractor and the trailer. An 18-wheeler will have a total of 18 rims with wheels on each rim. It has a total of 10 rims/tires on the truck/trailer and 8 rims/tires on the trailer. On the front of the semi (steer axle) there is a wheel on each side of the semi , and eight tires with rims on the back of the semi (drive axles), and then there will be eight tires with rims on the trailer that the semi is connected to, which equals eighteen wheels.

I have included a picture below to help you understand the number count.

One more thing, if you are looking for a clear explanation of what a tractor trailer is then check out this article I wrote which also includes a picture.

Notice the tractor has a total of 10 rims/tires and the trailer has 8 rims tires making 18 total rims/tires.

Why Do They Call It An 18-Wheeler?

The reason it is called an 18-wheeler is because a semi truck or tractor trailer has 18 wheels, there are 18 rims/tires total. 

The truck/tractor has one wheel on each side of the front of the truck/tractor (steer axles), then the semi truck/tractor has eight wheels on the rear of the semi truck/tractor.

The trailer that the tractor is connected to has eight wheels, so in total there are 18 wheels.

What is the Difference Between a Semi and an 18-Wheeler?

There is no difference between a semi truck and an 18 wheeler, they are different names for the same thing.

A semi truck refers to the truck or tractor that has the engine.

The semi can be driven without having a trailer attached to it.

An 18-wheeler is the semi truck attached to a semi trailer.

The two together is known as an 18-wheeler, because there is a total of 18 wheels with the combination.

The term “18 wheeler” and “semi truck” are often used by people describing the same thing, a truck/tractor with a trailer attached to it like the one in the picture above.

How Many Wheels Does an 18-Wheeler Have?

An 18-wheeler has 18 wheels.

The tractor has ten wheels. There are two wheels on the front of the tractor, and the rear of the tractor has eight wheels.

The trailer that the tractor is connected to has eight wheels on the rear of the trailer.

The rear wheels on the tractor and the rear of the trailer are dual wheels, which allows the weight of the truck and trailer to be distributed better.

Why Do Americans Call Trucks Tractors?

Usually, when someone in America is talking about a tractor, they are referring to a tractor that is being used on a farm.

During the early days of trucking, any big truck that was pulling a trailer was called tractors, because they were pulling the trailer.

Today, most Americans say big truck, semi truck, an 18-wheeler instead of calling the trucks a tractor. Here are other common names for an 18-wheeler:

• Semi-trailer
• Big rig
• Tractor trailer
• Truck and trailer
• Semi

What is a Semi Truck?

A semi truck a combination of a truck/tractor and a trailer.

The semi truck usually has 18 wheels and they are known as an 18-wheeler, big rig, tractor trailers, semi-trailers, semi tractor trailers, or just semis.

A semi trailer is attached to the fifth wheel coupling (also known as the hitch) on the tractor.

Together they are a semi truck.

A semi truck is a truck that has an engine. A semi truck doesn’t have to have a trailer attached to it to travel.

An 18-wheeler is the semi truck and semi trailer combination.

The tractor is connected to the trailer and together they have 18 wheels.

There are several different types of semi trailers, which include:

• Flatbed
• Reefer
• Dry Van
• Lowboy
• Double Drop
• Stretch Double Drop
• Multi Car
• Specialty

Why Do They Call It a Semi Truck?

A semi truck is called this because it refers to the truck or tractor has a trailer attached to it. There are several different semi truck types such as:

• Day Cab – The day cab semi truck doesn’t have any sleeping area. The day cab was designed for day trips where the driver doesn’t have to sleep in the truck. These are used for local drivers.

• Mid Roof Sleeper – The mid roof sleeper semi truck has a higher roof in the seventy-six-inch sleeper.

• Flat Roof Sleeper- The flat roof sleeper semi truck has a sleeper cab area along with storage compartments. There is less head space due to the flat roof design.

• Raised Roof Sleeper – The raised roof sleeper semi truck has more space due to the high roof in the sleeper area. The sleeper area has plenty of space for a flat screen television, along with compartments for storage.

History Of The 18-Wheeler

It is believed that in 1934 was the first known of an 18-wheeler being used.

Alexander Winton created the first semi during the late 1890’s, because he wanted to be able to haul cars that he sold to buyers all over the country, so the new cars would be delivered without any wear and tear on them.

In the 1910’s, August Charles Fruehauf made something similar so he could haul his boat. In 1934, the term 18-wheeler took off, because wartime equipment, logging, and new cars needed to be delivered with one vehicle, which became the 18-wheeler.

Today, there are over a million 18-wheelers on the roads in the United States. (source)

More Information About The 18-Wheeler

An 18-wheeler is essential in the United States.

An 18-wheeler hauls essential produce and goods every day.

Without 18-wheelers the economy would be impacted. In the United States, over 150 billion miles is done with an 18-wheeler each year.

Today, nearly three million 18-wheelers are registered in the United States.

Fun Facts About Semi Trucks

In the United States there are over two million semi trucks.

A semi truck can haul 80,000 pounds in the United States, but in Australia, they can haul up to 300,000 pounds with the four trailers or known as “road trains” that they can haul.

Nearly seventy percent of all goods are hauled and delivered with a semi truck in the United States.

In the United States, there are over three million over the road truck drivers.

Freightliner is the top semi truck brand. Annually, they sell 190,000 Freightliner semis. Freightliner will be introducing their all electrical semis called the Freightliner e-Mobility.