Understanding Why Some Truck Wheels Do Not Touch the Ground

Many truck owners and operators may notice that some truck wheels do not touch the ground at various times. This can be due to multiple factors, including design elements and operational conditions. This article will explore the key reasons why this phenomenon occurs and how it affects truck performance and safety.

Key Reasons Behind Suspended Wheels

Dual Wheels
Many trucks, especially heavy-duty ones, have dual rear wheels, with two wheels on each side. In some cases, the inner wheel might appear not to touch the ground due to load distribution or suspension design.
Suspension Design
Trucks commonly use air suspension systems, which allow for adjustments in ride height. When the truck is unloaded or positioned in a specific way, some wheels may lift off the ground.
Articulated Trucks
In cases of articulated trucks, such as those used for towing, the pivot point may cause certain wheels to lift off the ground during turns or when on an incline.
Weight Distribution
If a truck is heavily loaded on one side, or if the load shifts, some wheels may lift off the ground.
Deflated Tires
If a tire is deflated or damaged, that wheel will not make proper contact with the ground.
Off-Road Conditions
In off-road scenarios, uneven terrain can lead to some wheels being lifted off the ground due to the truck's articulation over obstacles.

Truck Design Innovations for Optimal Operation

Truck manufacturers have developed innovative solutions to manage weight distribution and improve fuel efficiency. One such example is the use of extra axles that can be raised off the ground. These axles are particularly useful when the truck is heavy but not necessary for empty or light loads.

Historical Background and Fuel Efficiency

The concept of temporarily raising wheels off the ground was introduced in the 1970s following the first "oil shock." Each tire encounters rolling resistance that must be overcome, and this requires fuel. The number and surface area of tires are designed to support the load properly when fully loaded.
The extra rolling resistance isn't necessary when a truck is unladen, so there is often a pair of wheels that can be raised off the road surface when the truck is empty, reducing fuel consumption and maintenance costs.
However, this feature is more commonly seen on heavy-duty vehicles like dump trucks, while its usage on semi-trucks is less frequent.

Conclusion

Understanding the reasons behind why some truck wheels do not touch the ground is crucial for safe and efficient operation of trucks. Whether due to design features or operational conditions, it's essential to be aware of these factors to ensure the truck performs optimally and the drivers remain informed about their vehicle's condition.