TruckingTruth logo

Section 13: Weight And Balance

A Brief History Of The Laws

The first truck weight limits were enacted in 1913 by Maine, Pennsylvania, and Washington. These laws were passed to limit damage to the dirt and gravel surfaced roads caused by the iron and solid rubber wheels of heavy trucks. Limits on length, width, and height were generally adopted somewhat later in most States. Ultimately, direct Federal involvement in regulation of truck size and weight limits did not occur until the passage of the Federal-Aid Highway Act of 1956.

Throughout the years, the States and the Federal Government have fought over who should have the right to set the standards for the size and weight of commercial vehicles. In the end, we have a system where the Federal Government issues legal minimums that the states must allow on Interestates and a set of highways commonly referred to as the "National Network", but the states also have the power to set their own standards to some degree. Hence, we have a mix of Federal and State laws to contend with.

Types Of Weight Limits

There are four basic weight limits: single axle, tandem axle, bridge formula, and gross vehicle. The Federal Standards are as follows:

  • 20,000 pounds single axle weight
  • 34,000 pounds tandem axle weight
  • 80,000 pounds gross vehicle weight
  • Bridge Formula Calculations

Why Do These Different Weight Limits Exist?

There are a long list of critical safety issues which require putting limitations on the gross weight, axle weights, the weight distribution across the length of a vehicle, and the weight distribution across a minimum number of axles.

  • Putting too much weight on a small area of the road surface can cause ruts, cracks, and potholes
  • Putting too much weight on a small area of a bridge surface can cause structural damage to the bridge
  • Too much weight on your steer axle can lead to a "heavy steering" feel and may cause the truck to react improperly to steering inputs
  • Not enough weight on your steer axle can lead to a loss of traction for your steer tires
  • Improper weight balance between your tractor drive tires and trailer tandems can lead to poor traction and an increased risk of jackknifing
  • Too much weight toward the back of the trailer can lead to a "pendulum effect", causing the rear of the trailer to sway back and forth while driving down the highway or jackknife going around a curve
  • Overloading a tire beyond it's maximum tire load capacity can cause tire damage and blowouts
  • Overloading the suspension system of the truck can cause damage to the suspension system which could easily lead to loss of control of the vehicle

So as you can see, it's critical in so many ways to make sure that the weight limits are followed in strict accordance with the law. It is incredibly dangerous to overload a vehicle or have the weight improperly distributed across the axles.

You will not be quizzed on these historical facts. This is to help you understand how and why the current laws came into being.
You will definitely need to know these. These are the basic weight limits you'll be dealing with under today's laws.
We will discuss the bridge formula soon.

Tandems:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

Tandem:

Tandem Axles

A set of axles spaced close together, legally defined as more than 40 and less than 96 inches apart by the USDOT. Drivers tend to refer to the tandem axles on their trailer as just "tandems". You might hear a driver say, "I'm 400 pounds overweight on my tandems", referring to his trailer tandems, not his tractor tandems. Tractor tandems are generally just referred to as "drives" which is short for "drive axles".

Review Questions - Click On The Picture To Begin...

What are the Federal standards for the gross vehicle weight of a 5 axle commercial vehicle?
  • 80,000 pounds
  • 65,000 pounds
  • 22,000 pounds
  • 60,000 pounds

Quote From The CDL Manual:

  • 20,000 pounds single axle weight
  • 34,000 pounds tandem axle weight
  • 80,000 pounds gross vehicle weight
  • Bridge Formula Calculations
Next
What is the Federal standard for the weight limit on a single axle?
  • 20,000 pounds
  • 12,000 pounds
  • 15,000 pounds
  • 22,000 pounds

Quote From The CDL Manual:

  • 20,000 pounds single axle weight
  • 34,000 pounds tandem axle weight
  • 80,000 pounds gross vehicle weight
  • Bridge Formula Calculations
Prev
Next
What are the four basic weight limits?
  • single tire, bridge formula, tri-axle, gross vehicle
  • double spacing, single axle, bridge forumula, overweight
  • single axle, tandem axle, bridge formula, and gross vehicle
  • single axle, tandem axle, single tire, eight tire

Quote From The CDL Manual:

There are four basic weight limits: single axle, tandem axle, bridge formula, and gross vehicle.
Prev
Next
What is the Federal Standard for maximum weight on a tandem axle vehicle?
  • 34,000 pounds
  • 27,000 pounds
  • 30,000 pounds
  • 37,000 pounds

Quote From The CDL Manual:

  • 20,000 pounds single axle weight
  • 34,000 pounds tandem axle weight
  • 80,000 pounds gross vehicle weight
  • Bridge Formula Calculations
Prev
Next
What can be the result of too much weight on the back of the trailer?
  • A "pendulum effect" causing the rear of the trailer to sway back and forth while driving down the highway or jackknife going around a curve
  • You won't be able to fuel up properly without being overweight
  • The steering will feel "heavy" and sluggish
  • The steer tires won't grip properly

Quote From The CDL Manual:

Too much weight toward the back of the trailer can lead to a "pendulum effect", causing the rear of the trailer to sway back and forth while driving down the highway or jackknife going around a curve

TruckingTruth's Advice:

Balancing the weight of your truck properly across the axles is a legal requirement because there are so many safety factors involved.
Prev
Finish
Please select an option
[1,1,3,1,1]
5

Join Us!

We have an awesome set of tools that will help you understand the trucking industry and prepare for a great start to your trucking career. Not only that, but everything we offer here at TruckingTruth is 100% free - no strings attached! Sign up now and get instant access to our member's section:
High Road Training Program Logo
  • The High Road Training Program
  • The High Road Article Series
  • The Friendliest Trucker's Forum Ever!
  • Email Updates When New Articles Are Posted

About Us

TruckingTruth was founded by Brett Aquila (that's me!), a 15 year truck driving veteran, in January 2007. After 15 years on the road I wanted to help people understand the trucking industry and everything that came with the career and lifestyle of an over the road trucker. We'll help you make the right choices and prepare for a great start to your trucking career.

Read More

Becoming A Truck Driver

Becoming A Truck Driver is a dream we've all pondered at some point in our lives. We've all wondered if the adventure and challenges of life on the open road would suit us better than the ordinary day to day lives we've always known. At TruckingTruth we'll help you decide if trucking is right for you and help you get your career off to a great start.

Learn More