Semi trucks have many wheels. However, this varies greatly on the weight being hauled and the class of the vehicle.
In this article, we explain how many wheels do the various types of semi trucks have.
Read on to find out more…
Here’s a Short Summary to How Many Wheels does a Semi Truck have:
A semi-truck will typically have either 6 or 10 wheels. A heavy-duty tractor unit will have 10 wheels, with 2 steer wheels on the front axle and 4 wheels on both of the rear axles. A medium-duty tractor unit will have 6 wheels, 2 steer wheels on the front axle, and 4 wheels on a single rear axle.
Table of Contents
How many Wheels does an 18 Wheeler have?
The number of wheels on an 18 wheeler usually corresponds to the number of rims on the semi truck.
18 wheelers usually have 18 rims and each has a tire. This means that most 18 wheelers also have 18 wheels.
This doesn’t look the same as it would on a regular car, however.
Usually on either side of the front of the tractor are 2 wheels (so 4 on either side of the front of the tractor) with the back set of wheels having 10 total on the tractor.
The double axle trailer has a total of 8 wheels with 2 wheels on either side of each axle. This means the trailer has 8, plus the 10 up on the tractor which equals to 18.
Do all Trucks have 18 Wheels?
No, not all trucks have 18 wheels. It is true that 18 wheelers all have 18 wheels, but semi trucks come in many sizes.
The next size down from an 18 wheeler is the 16 wheeler.
The 16 wheeler is similar, but smaller, with a smaller engine, and of course 16 instead of 18 wheels.
The confusion arises in part because of the common use of the term 18 wheeler to refer to any semi truck.
However, the number of wheels a truck has will depend on how many axles it has and whether it has single-tire hubs or double-tire hubs. This applies to both the tractor unit and the trailer.
Why do 18 Wheelers have 16 Wheels?
16 wheelers are uncommon, but they do exist.
18 wheelers only have 18 wheels and do not have fewer or more. But, semi trucks have fewer wheels to haul small loads and less weight.
A 16 wheeler semi truck may exist if you have a tractor unit having 10 wheels, similar to that of an 18 wheeler, and a trailer with a 6 wheel configuration.
A trailer with a 6 wheel configuration will typically consist of 3 axles with single-tire hubs, totaling 6 wheels.
These types of trailers are used for lighter loads and are most common in Europe.
How many Wheels do Semi Trucks have?
Most semi trucks with a tractor and trailer configuration have 18 wheels, hence the ubiquitous name.
However, semi trucks can have fewer wheels and if extra trailers are being hauled, this will also increase the number of wheels the truck has.
A tractor unit typically has 6 or 10 wheels. A light-duty tractor unit has 6 wheels whilst a heavy-duty tractor unit will have typically have 10 wheels.
If a semi truck is hauling two trailers, each trailer can add an extra 4-12 wheels depending upon the rim set up.
Some semi truck rims are designed for two wheels each, while others only have one rim for one wheel.
A typical heavy-duty trailer in the U.S. has a double or tri-axle setup, both with double-tire hubs.
Therefore a double axle trailer will have 8 wheels and a tri-axle trailer will have 12 wheels in total.
How many Wheels do Light to Medium Duty Semi Trucks have?
These semi trucks will include primarily class 5-6 trucks. The trucks include vehicles such as box trucks, some moving trucks, and delivery trucks.
Some smaller, lighter-duty semi trucks can have as little as 6 wheels. These typically have a single rimmed wheel and a smaller trailer.
A medium-duty tractor like the Kenworth T270 and T370 has 6 wheels, 2 as the front steer tires, and 4 wheels in the rear axle.
How many Wheels do Heavy Duty Semi Trucks have?
The heavy-duty semi trucks are when the rims of their wheels usually support more than one tire.
This is when you will start to see the class 7-9 semi trucks with 18 wheels.
This class, as stated above, includes the large to oversized load semi trucks. Class 7 can include some street cleaning trucks and garbage trucks which are large and typically have 10 wheels.
A heavy-duty tractor like the Peterbilt 389 will have 10 wheels, 2 as the front steer tires, and 8 wheels in the 2 rear axles.
Together with a trailer, it can add up to 6 – 24 wheels, depending on the number of axles per trailer and of course whether it utilizes single-tire or double-tire hubs.
The larger semi trucks with a single trailer have between 16-18 wheels for the trucks registered for up to 30,000 pounds and up to three axles.
Oversized loads may have an extra row of double tires in the back of the trailer, thus making the total 20-24 wheels.
How many Wheels do 6×2 semi Trucks have?
The 6×2 semi trucks typically have 6 wheels. 2 steer wheels on the front axles and 4 wheels on the rear drive axles.
The 6×2 semi trucks essentially mean that the two of the rear-drive axles get powered. For this reason, it is better suited for class 6 vehicles that do not haul as much weight.
These are more popular in Europe but have been gaining traction in the U.S.
One of the main appeals of this design is it saves fuel, but also delivers less power so be sure you know your routes before making your choice.
How many Wheels do 6×4 Semi Trucks have?
The 6×4 semi trucks typically have 10 wheels. 2 steer wheels on the front axles and 4 wheels each on the 2 sets of rear drive axles.
Similar to the answer above, 6×4 essentially means of the 4 of the rear axles are being powered which makes it the drive axles. For they are more powerful than 6×2.
These semi trucks use much more fuel than the European styled 6×2, but it is preferred by drivers who travel in rough terrain.
Typically, 18 wheelers use 6×4 wheel drive, which means usually they have 18 wheels total.
How many Wheels do 6×6 Semi Trucks have?
The 6×6 semi trucks typically have 10 wheels. 2 steer wheels on the front axles and 4 wheels each on the 2 sets of rear drive axles.
All 3 sets of axles are powered i.e. 6 axles in total.
The 6×6 semi truck is sometimes called all-wheel drive. For small cars this is known as 4×4 all wheel drive, but since there are more wheels on a semi truck, it is 6×6.
Usually, these trucks are not used for commercial use. Rather, it is reserved for military vehicles such as tanks and off-road all-terrain vehicles.
What is the Maximum Number of Wheels in a Truck?
The maximum number of wheels in a standard truck is 22. This truck will consist of a heavy-duty tractor unit with 10 wheels and a tri-axle trailer with dual-tire hubs having 12 wheels. However, semi trucks that haul oversized loads will have more wheels and must acquire special clearance.
Do all axles in a Semi have Double Wheels on Either side of them?
Most semi trucks of the 7-8 class need to have double tires. This is due in part to the fact that these wheels operate with the 2-3 axles to get their power and balance the weight of the load.
For semi trucks weighing up to 80,000 pounds, you will definitely want to have the double tire in order to hold so much weight.
If you consider class 5-6, however, the weight is not so great that the wheels cannot hold it.
Typically, all semi trucks (especially the big rigs people have in mind) need the extra wheels. But, smaller models which carry less weight at once don’t need the support.
How many Steering Wheels does a Semi Truck have?
A typical tractor unit will have 3 sets of axels.
The front set of axles will have two steer wheels, one on either side.
The other 2 axles are considered as the drive axles and will have 2 wheels on either side of each axle.
The steer wheels are controlled by the steering wheel which is located in the driver’s cab.
Why do Large Trucks have so many Wheels?
One of the main reasons there are so many wheels on a semi truck is to balance the weight and ensure the weight is supported.
This prevents the pressure of up to 80,000 pounds from crushing the tires or causing them undue wear.
For this reason, the tire lifespan is actually extended by having support from the others.
Another reason is to keep the vehicle balanced when turning and traveling. There is a lot of weight that can cause the semi truck to tilt or fall if the wheels cannot hold the weight.
Why do Big Trucks have Wheels that don’t Touch the Ground?
There are a lot of rules and regulations on semi truck weight limits that must be adhered to and can easily be unbalanced due to loads.
Most commonly these wheels are on dump trucks and garbage trucks which can very easily exceed the legal load limits.
But, these wheels are not always needed and thus can be raised when the weight limit isn’t being exceeded.
One reason it is good to have the option to raise the extra wheels is the more axles that are in use the less mobile your truck will be.
If more axles are being utilized it can make turning more difficult, so you don’t want to have them implemented unless needed.
How many Spare Wheels does a Semi Truck have?
This depends upon the type of truck you are thinking about.
Most big rig, 18 wheeler semi trucks do not carry spare tires with them or have the extra raised wheels seen on garbage and dump trucks.
The reason many big rigs do not carry spares with them is that it will upset the weight limit of the trailer.
Tractor-trailers need to be very careful they do not exceed weight limits when they enter the weigh station. Having a spare tire will add to the overall weight of the truck and make it more difficult to travel.
It is also far easier to have assistance rather than try to somehow change the semi truck’s tires on the highway without proper equipment.
All in all, semi trucks do not benefit from having any spare tires with them.
Garbage trucks and dump trucks can have as many as 3 extra sets which can be lowered and used, but typically only have 1-2 rows.