Semi Truck and Trailer Questions

5 min readDec 20, 2022

Here are some answers to some basic questions people ask about semis and semi-trailers.

Semi Truck

How much are semi trucks?

Semi Trucks cost anywhere from $35,000 to over $200,000 depending upon if it is used or new and if it is a low-end or high-end truck.

Low-end trucks are usually under $100,000 while high-end trucks run about $150,000 or more. When purchasing a truck there are these factors to consider.

A new semi-truck will cost anywhere from $75,000 to $200,000 depending on what options you pick.

New or Used
New may be expensive but you will have a few repair bills and you can customize the truck to meet your needs.
Used may be cheaper but expect repair bills to pop up and if you cannot make the repairs yourself this may not be an option plus you will be limited with the options of what you pick.
Buying a used truck with over 600,000 miles is when it starts to nickel and dime you to death.

Why are semi-trucks called semi-trucks?

You may think that the word “semi” relates to the size of the truck but that is not true. Especially when it weighs more than 80,000 pounds when hauling a load (The max allowed in the United States). “Semi” has nothing to do with the size of the truck but has to do with what the tractor is pulling behind it. Since the tractor unit can detach from the trailer unit. That gives semi-trucks a unique advantage over rigid trucks and trailers.

A rigid truck and full trailer are articulated inside the cargo area length, so a semi-trailer can have a longer continuous cargo area. Because of this, a semi-trailer can haul longer objects, (logs, pipes, beams, railway tracks).

How many semi trucks are in the US?

There are over 15 1/2 million trucks on the road. You can read more about this and trucking companies in our article, “How many trucking companies are in the USA?“

How many miles do semi trucks last?

On average, a semi will last 750,000 to 1,000,000 miles. We have a detailed article on the hows and whys of this that you can read at “How Many Miles do Semi Trucks Last?“

How much do semi-trucks weigh?

Depending upon if it is a sleeper cab or not, the size of the motor, and how much weight it is designed to haul the weight of a semi-truck can range from 10,000 to 25,000 pounds.

A semi-truck with an empty trailer will weigh about 35,000 pounds.

The most a semi with a loaded trailer can weigh in the United States is 80,000 pounds.

Why do semi trucks have spikes on their wheels?

While some people think that the spikes are purely for looks they actually serve a purpose. The lug nut spikes you see on semi-trailers actually protect the lug nuts from weatherized corrosion from being on the road for so long and also help direct moisture away from the tire while it is spinning as well.

What engine do semi trucks have?

The normal engines that semi-trucks use are diesel engines because it gives them better hauling power and torque (1,850 lbs of torque) than gasoline engines. The average class 8 semi-truck engine is a 14.8 liter 6 cylinder motor that weighs over 2,800 pounds with 560 horsepower.

There is a new trend of semi-motors cropping up with electric motors. Electric motors can still monitor the engine components’ operation and generate diagnostic codes when there is trouble. The electric motors have the same torque but at lower RPMs, it has much more torque than what a diesel engine can provide.

Experts say that another major advantage of electric motors over diesel motors is that is can provide regenerative braking which can send a charging current back into the batteries which lowers operating costs and extends the range of the motor. This also, in turn, reduces brake pad and lining wear.

When were semi trucks invented?

The first semi-truck was created and sold in 1898 by Alexander Winton with its internal combustible engine (ICE).

Semi Trailer

What is a semi-trailer?

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 semi-trailer; a tractor-trailer.

There are many types of semi-trailers including:

Box or Van Trailers (most common)
Bus-Bodied Trailers (bus contacted to a semi)
Car Carrier Trailers (car hauler)
Conestoga (flatbed trailer with retractable top)
Curtain Siders (Flatbed with tarps on the side)
Drop Deck Trailers (the floor drops down)
Double Deckers (2nd-floor trailer)
Dry Bulk (powder tankers)
Dump Trailers (like a dump truck)
Flatbeds (floor only or removable sides)
Hopper Bottoms (allow dumping from below)
Inloaders (used to transport glass safely)
Intermodal Trailers (closed van semi-trailer that is either owned or controlled by a railroad, leasing company, or motor carrier)
Live Bottom Trailers (conveyor belt on the floor to move cargo out)
Livestock Trailers (haul animals)
Low Boy (low-floor flatbed)
Refrigerator Trailers (move cargo that needs refrigeration)
Refrigerator Tank Trailers (move liquid cargo like milk that needs refrigeration)
Sidelifter (aka Sideloader that allows movement of cargo without a forklift)
Side Bay (doors on side of the trailer)
Tank Chassis (aka Tankers that move liquid cargo that does not need refrigeration)
Frac Tank Trailer (single-axled trailer used hydraulic fracturing at oil wells)
Wing Trailers (hybrid between a curtain sider and a box trailer with gull-wing style doors)

Semi-trailer dimensions

For the LCD (least common denominator) by law, the max-width has to be 8 feet wide, 13.5 feet tall, and 40 feet long.

How wide is a semi-trailer?

On average it is about 8.5 feet wide for a Box or Van Trailer.

How long is a semi-trailer?

The average is 72 feet long but if you see the number 53 on the side of a trailer that means that it is 53 feet long and is also very common.

How tall is a semi-trailer?

On average a Box or Van Trailer is 13.5 feet tall.

How much does a semi-trailer weigh?

A common 53-foot semi-trailer weighs about 10,000 pounds.

The article was written by Michael Rock of The Internet Presence, LLC, and US Special Delivery is the source.