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How Many Wheels Does a Semi Truck Have?

How Many Wheels Does a Semi Truck Have?

A semi-truck is an 18-wheeler with five axle settings and can attach different trailers. However, the light-duty units have six tires, and heavy-duty may have up to 10 wheels on both axles. 

How Many Wheels Does a Semi Truck Have? A semi-truck has 18 wheels on the tractor and trailer and has five-axle, a steering axle on the tractor, and four rear axles on the trailer; a 6×4 drivetrain has six wheels with three axles, 4WD. A 6×2 configuration has a tri-axle setting with two steering and four trailer wheels, and a 6×6 is a 6-ton unit with ten wheels. Peterbilt 389 has ten tires, the light-duty semi-trucks have 4 to 6 tires, and Kenworth has six wheels on the front and rear axle. 

These eighteen wheels support the cargo, keep the tractor stable and protect the sudden truck failure. There are around 4 million semi-trucks, and equal weight and pressure distribution prolong the lifespan of semi-trucks. 

What are the average numbers of wheels a semi-truck has?

The heavy-duty semi-trucks have 18 wheels with a specific alignment. They have segregated tires on the steering cabin and trailer. 

They have eighteen rims with rubber wheels on them. On the front axle, the steering compartment has one wheel on both sides of the tractor.

The 18-wheelers have five axles with different configurations. The steering compartment has only one axle on the front side that holds a pair of tires. 

The cargo section has four axles, and its front section has double axles on a similar unit. However, the backside has a similar number of axles that connects to hold eight tires.

On the cargo, the semi-truck has two axles on the front and rear sides. The front axle comprises a pair of tires on both sides of the unit. It indicates that the trailer’s front axle has eight rims with wheels. 

On the rear axle, the tractor-trailer has eight rims and wheels. With additional trailers, the number of tires varies.

But, they have eighteen wheels on different variants. However, a light-duty semi-truck has 6 to 10 wheels. 

Typically, the heavy-duty setups have ten wheels on the steering and rear section. As a result, they can haul two trailers simultaneously with an extra 4 to 12 wheels. 

According to the rim setup, their number varies in coordinated pairs. In addition, the heavy-duty vehicles have tri or double-axle configurations across the USA. 

Both setups have dual tire hubs with variable mileage. The cargos with double axles have eight wheels, and the tri-axle has 12 wheels on these variants. 

What is the number of wheels on different axle configurations?

They have different axle configurations to determine the position of wheels on the front and rear compartments. Following are three significant settings that specify the weight distribution over the tires. 


A 6×4 drivetrain is one of the most famous configurations for semi-trucks. The setting indicates that the steering cabin has six wheels. 

Three tires are on either side of the unit with extensive stability and support. However, their engines supply power to four positions on the rear side of the tractor. 

It has three axles that deliver power to the ends of two wheels. Typically, these setups have 4WD and lack the all-WD. 

These variants have six wheels with an attached cargo. Two of them are steering wheels which are present on the front axle of the tractor-trailer.

They have four wheels with two sets on both sides on the rear drive axle. 6×4 drivetrain shows that the four of the back axle get the electric power.

Their axles drive the truck in the forward direction and repel the aerodynamic effects. They are more energetic than any other configuration due to their settings.

They consume excessive fuel because they provide stable results on rough and unstable terrain. With a 6×4 configuration, these massive units use 18 wheels.


It is a classic configuration with a tri-axle tractor. The power travels to the tandem rear axle of the semi-truck. It has six wheels, and only two have the energy to drive the truck.

It has two steering tires that work on the front axles with six wheels. However, its four tires are on the back axles and drive the unit forward.

The rear drive axles get the maximum power and stabilize the truck on different road surfaces. Class 6 vehicles use the 6×2 settings, haul massive loads and keep the frame intact for a long duration.

They facilitate one of the highest traction across the USA. They are fuel-economical units that save fluid due to built-in technologies.

With less fuel consumption, they supply lower power to the rotational components. 


The heavy-duty setup has a 6×6 setting due to its massive load-carrying capacity of around 6 US tons. 

These units have a classic and traditional cargo section that withstands all the drive terrains and fluctuating weather conditions.

They have an all-wheel drive with three axles. They have two wheels on each axle which drive the truck simultaneously. The engine supplies equal power to the six wheels and moves them forward.

Generally, the 6×6 semi-trucks have ten wheels. 

They exist on the drive axles with two wheels on both sides. According to 6×6 settings, the tri-axle gets the equivalent amount of energy.

They have an all-WD but cannot work on a commercial level. They are all-terrain, off-road units for interstate and local shipment activities. 

How many wheels does a Heavy duty semi-truck have?

They are class 7 and class 9 semi-trucks with 18 wheels. Their one rim supports more than a single tire. The heavy-duty class includes oversized and large tractor-trailers.

Its class 7 has a few small units that can pick garbage from the roads. However, they are massive, heavy-duty units with 10 wheels. 

Peterbilt 389 is a heavy-duty truck that has ten wheels. Its two tires are on the front side that are steering axles.

However, the rear axles have two sets of four wheels. The dual axles are on the backside. They have eight tires on both sides of the truck.

It can attach massive cargo sections, which comprise 6 to 24 wheels on the tractor and hauling unit. Their number varies according to the number of axles on each cargo.

They have single or double hubs for tires. The largest semi-trucks with a single cargo comprise between 16 to 18 wheels. Their trip-axle settings can register the weight handling limit of around 30000 to 31000 pounds. 

They are oversized units with double tires on the backside for the trailer. In such circumstances, the total number of wheels becomes 20 to 24 wheels. 

Number of wheels in a light-duty semi-truck

Class 6 and Class 5 trucks are primarily part of these semi-trucks. In addition, they include the box and delivery trucks. The light duty and smaller units have 4 to 6 wheels.

They have a wheel with a single rim and attach a smaller cargo. Kenworth 370 is a light-duty tractor-trailer with six wheels.

It has two front wheels that provide the steering force. On the rear side, it has four wheels that resist drag. 

Why do semi-trucks have so many wheels?

They have 18 wheels to support the frame, transmission, and suspension. Due to the following reasons, these units have multiple tires on the front and rear sections. 

Equivalent weight distribution

These trucks have double and triple axles with pairs of wheels. They have several tires on the tractor and cargo for equivalent weight distribution.

The heavy loads of cargo put pressure on the tires. However, with stable weight scattering, the trucks remain stable on bumpy and off roads.

Durable performance

These variants last longer than other hauling trucks due to multiple tires. The pressure distributes on the rear and front parts. 

As a result, the risks of internal damages reduce. They are complex units with advanced steering and sideway scrubbing.

Their tires mount in the form of clusters to withstand the pressure of massive cargo. With stable rotational parts, the tractor-trailers last longer than their standard lifespan.

Stability of the cabin and trailer 

The rear wheels stabilize the cabin and the cargo material on uneven roads. The front steering tires keep the tractor intact and support high speed.

These variants have separate tires on the front and rear units to match their speeds. The cabin and trailer units move forward with identical road drag. 

The cargo achieves more traction on the bumpy roads and ships the material to long-distance places. 

Protection from sudden failure

The multiple wheels stabilize their internal parts, rubber, and rims from wearing and tearing. One tire can burst due to excessive load and cargo pressure.

However, the bursting of tractor tires affects the performance of the rear cargo. 

In such circumstances, replace the damaged part and drive the hauler at optimized speeds. 

Shipment of heavy loads 

The semi-tractors attach the massive trailers on their rear side. They deliver heavy loads to long-distance places without sudden failure or swaying.

The 18 wheels support the tractor and trailer simultaneously. They withstand loads of cargo and transfer them without damage. Its tractor shifts the front load to the rear wheels with inappropriate tire performance.

Better off-road driving

The 18-wheelers have smooth riding on off-roads due to multiple tires. They absorb the effects of bumps due to multi-layered rubber materials. 

They keep the semi-truck stable on hills and sloppy roads. With high-performance diesel engines, these trucks resist road obstacles. 

They can cover thousands of miles without significant frame or suspension damage.

However, the tires coordinate with the brakes and steering wheel. Their appropriate alignment results in improved and stable driving conditions.

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