Understanding Differential Axle Speed in Trucks

“The front wheel rolls, the rear follows, the two rear wheels just carry the load.” This humorous saying reflects the difference in speed between the two wheels on a truck’s drive axle. What is this difference, and how does it impact operation and safety? Let’s explore.

Why Compare Drive Axle Wheel Speeds?

Before comparing, let’s understand why this speed difference matters.

• Technical Perspective: Trucks use differentials to allow wheels on the same axle to rotate at different speeds when turning. This ensures smooth turning and prevents skidding.
• Safety Perspective: Excessive speed differences between drive axle wheels can cause loss of control, endangering the driver and others.
• Economic Perspective: Understanding and managing this difference extends tire life, reduces wear and tear, and improves fuel efficiency.

Differential and wheel speed

Do Drive Axle Wheels Rotate at the Same Speed?

The answer is NO.

When driving straight, both drive axle wheels rotate at nearly the same speed. However, when turning, the outer wheel travels a longer distance than the inner wheel in the same amount of time. Therefore, the outer wheel rotates faster.

How a Differential Works

The differential plays a crucial role in distributing torque and allowing the drive axle wheels to rotate at different speeds during turns. This allows for smoother, safer cornering.

Common Scenario: Skidding During Turns

A common issue with trucks is skidding during turns. This can be caused by various factors, including an excessive speed difference between the drive axle wheels. The differential may not be able to distribute torque effectively, leading to a loss of control.

Truck skidding on a turn

Handling a Skid

If your truck begins to skid, remain calm and take these steps:

• Ease off the accelerator.
• Steer in the direction you want the vehicle to go.
• Avoid slamming on the brakes.

Related Questions

Beyond comparing drive axle wheel speeds, you might be interested in:

• How does a differential work?
• What are the common types of differentials?
• How do I maintain a differential?
• What are the signs of a failing differential?

Related Products

You can also explore differential-related products here.