CDL Practice Tests: Weight & Balance

Choose A Section:

Go!
Question #619 (1 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

What is the Federal standard for the weight limit on a single axle?

  • 22,000 pounds
  • 20,000 pounds
  • 12,000 pounds
  • 15,000 pounds
  • 20,000 pounds single axle weight
  • 34,000 pounds tandem axle weight
  • 80,000 pounds gross vehicle weight
  • Bridge Formula Calculations
Previous Next
Question #626 (2 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

Sliding your trailer tandems forward or backward will redistribute the weight mainly between which two sets of axles?

  • Steer axle and drive axles
  • Steer axle and trailer tandems
  • None of these answers are correct
  • Drive axles and trailer tandems
Sliding your trailer tandems forward or backward will redistribute the weight mainly between your drive axles and trailer tandems
You may find a slight change in the weight of your steer axle after sliding your tandems, but it won't be very much and it's rarely much of a concern.
Previous Next
Question #634 (3 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

What is low-speed offtracking?

  • When a trailer's tandem axles are slightly out of alignment, the rear of the trailer will track off to one side or another instead of directly behind the tractor
  • When taking off from a dead stop, the initial torque of the engine on the drivetrain will cause a slight offtracking of the tractor which could be a hazard to other traffic
  • When a combination vehicle makes a low-speed turn the wheels of the rearmost trailer axle follow a path several feet inside the path of the tractor steering axle.
  • When making a high speed turn, the momentum carried by the trailer will cause it to swing wide and possibly outside the lane of travel
When a combination vehicle makes a low-speed turn - for example a 90-degree turn at an intersection - the wheels of the rearmost trailer axle follow a path several feet inside the path of the tractor steering axle. This is called low-speed offtracking.
Previous Next
Question #624 (4 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

In the following picture, what are axles 4 and 5 commonly referred to as?

  • "back set" or "rear tandems"
  • "trailer drives" or "back tandems"
  • "trailer set" or "back tandems"
  • "tandems" or "trailer tandems"
#4 and #5 together are your trailer tandem axles (commonly referred to as "tandems" or "trailer tandems")
You'll generally hear drivers refer to these axles as simply "tandems". They'll say "The load I had yesterday was loaded incorrectly and I was overweight on my 'tandems' ".
Previous Next
Question #673 (5 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

Using the following numbers for your calculations, how much weight will come off your drive axles?

Miles per gallon: 6
Miles travelled: 360
Percentage of fuel weight on drive axles: 30%

  • 200 pounds
  • 144 pounds
  • 300 pounds
  • 210 pounds
To calculate the percentage of a value, you simply multiply the total value times the percentage you're looking for, and then divide by 100.
If you're getting 6 miles per gallon and you travel 360 miles:

360/6 = 60 gallons of fuel

60 gallons x 8 pounds per gallon = 480 pounds of total fuel burned off

Since 30% of the weight of fuel goes on our drive axles, we need to know what 30% of 480 is:

30 x 480 / 100 = 144 pounds coming off the drive axles
Previous Next
Question #620 (6 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

What is the Federal Standard for maximum weight on a tandem axle vehicle?

  • 30,000 pounds
  • 34,000 pounds
  • 37,000 pounds
  • 27,000 pounds
  • 20,000 pounds single axle weight
  • 34,000 pounds tandem axle weight
  • 80,000 pounds gross vehicle weight
  • Bridge Formula Calculations
Previous Next
Question #662 (7 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

What is the correct method of determining what percentage of fuel is distributed between the steer axle and the drive axles?

  • Weigh the truck after running 100 miles, then immediately fuel up, and then re-weigh the truck to see what percentage of the added weight went to the steer axle, and what percentage went to the drive axles.
  • Weigh the truck, then drive exactly 100 miles, and then re-weigh the truck to see what percentage of the added weight went to the steer axle, and what percentage went to the drive axles.
  • Weigh the truck, then immediately fuel up, and then immediately re-weigh the truck to see what percentage of the added weight went to the steer axle, and what percentage went to the drive axles.
  • Weigh the truck immediately after fueling, then run exactly 100 miles, and then re-weigh the truck to see what percentage of the added weight came off the steer axles.
In order to accurately determine what percentage of fuel weight goes to your steer axle versus your drive axles you can simply weight the truck, then immediately fuel up, and then immediately re-weigh the truck to see what percentage of the added weight went to the steer axle, and what percentage went to the drive axles.
Previous Next
Question #641 (8 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

Which of the following has the greatest affect on the gross vehicle weight?

  • Moving the cargo toward the front or rear of the trailer
  • The position of the tractor's 5th wheel
  • None of these affect the gross vehicle weight at all
  • The position of the trailer's tandems
The final key point to understand when it comes to weight transfer is that none of the methods of redistributing weight between the different sets of axles, including sliding your 5th wheel, sliding your tandems, or moving the cargo around will have any affect on your gross weight.
The only way to affect the gross vehicle weight is to add or remove weight from the vehicle. The methods of weight transfer we've discussed will move weight from one area of the vehicle to another, but will not affect the gross weight of the vehicle itself.
Previous Next
Question #644 (9 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

What affect will sliding the trailer tandems forward have on the weight distribution?

  • You will take weight off the tractor's drive axles and put more weight on the steer axle
  • You will put less weight on the trailer tandems and put more weight on the tractor's drive axles
  • You will put more weight on the steer axle and take weight off the tractor's drive axles
  • You will put more weight on the trailer tandems and take weight off the tractor's drive axles
By sliding the trailer tandems forward, you will put more weight on the trailer tandems and take weight off the tractor's drive axles.
Previous Next
Question #627 (10 of 10)

Give a brief explanation of the problem:

Optional: Leave your email address if you would like a reply:

Report Cancel

Sliding your 5th wheel will redistribute the weight mainly between which two sets of axles?

  • Steer axle and drive axles
  • Steer axle and trailer tandems
  • Trailer tandems and rear axles
  • Drive axles and trailer tandems
Sliding your 5th wheel will redistribute the weight mainly between your steer axle and your drive axles
Sliding the 5th wheel will generally have little or no effect on the weight of your trailer tandems
Previous Next
Complete!

Choose your next section:

Go!

About The Weight And Balance Section

This section was created by Trucking Truth to help people understand how to load cargo, scale the truck, and understand the laws about truck weight limits. These materials will not be on your written CDL exams but it is critical that every truck driver knows these materials.

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 we follow the weight limits in strict accordance with the law. It is incredibly dangerous to overload a vehicle or to have the weight improperly distributed across the axles.

Methods Of Weight Transfer

There are several ways to distribute the overall weight of the vehicle across the different sets of axles. You will affect weight distribution by:

  • Changing the weight distribution of the cargo along the length of the trailer, or moving the cargo around after loading the truth. This will distribute the weight mainly between your drive axles and trailer tandems
  • Sliding your trailer tandems forward or backward will redistribute the weight mainly between your drive axles and trailer tandems
  • Sliding your 5th wheel will redistribute the weight mainly between your steer axle and your drive axles
  • Adding or burning off fuel will mainly change the amount of weight on your steer axle and somewhat on your drive axles also, depending upon the placement of your fuel tanks.

Limitations On Weight Transfer

There are several factors that will reduce the amount of weight we can transfer between the different sets of axles on the truck:

  • Federal laws limit the maximum weight on any set of axles and the gross vehicle weight - 20,000 pounds single axle, 34,000 pound tandem axles, 80,000 pounds GVW
  • The bridge law formula limits the maximum amount of weight you can carry across any set of axles based upon the number of axles and the spacing between them (we'll discuss this formula soon).
  • The maximum legal length allowed between your trailer kingpin and your trailer tandems will limit how far back you can slide your tandems
  • The load rating of the tires you have will determine the maximum amount of weight allowed on any particular tire
  • The load rating of the suspension system will limit the amount of weight you can have on any axle

The Bridge Formula

bridge law formula and regulations for trucks

Congress enacted the Bridge Formula in 1975 to limit the weight-to-length ratio of a vehicle crossing a bridge. They accomplished this either by spreading weight over additional axles or by increasing the distance between axles.

The idea here was to prevent putting too much weight on a relatively small area, causing damage to the road surface and bridge structure. By requiring trucks to spread the weight across a longer distance and distributing the weight across more axles, you help prevent damage to the bridges and roadways.

Compliance with Bridge Formula weight limits is determined by using the following formula:

W = the overall gross weight on any group of two or more consecutive axles to the nearest 500 pounds.

L = the distance in feet between the outer axles of any group of two or more consecutive axles.

N = the number of axles in the group under consideration.

Altering The Weight Distribution

The primary factors which will affect the weight distribution across a truck's axles are:

  • The position of the trailer's tandems
  • The position of the tractor's 5th wheel
  • The overall weight of the cargo in the trailer and the horizontal (front-to-back) position of its center of gravity
  • The amount of fuel onboard and the placement of the fuel tanks

In the coming pages, we'll go through these one at a time and learn to apply each one individually. Later we'll put them all together and show you how to get your truck's weight distribution legal out on the highways, coast to coast, under any circumstances.

Why Join Trucking Truth?

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

Apply For Paid CDL Training Through TruckingTruth

Did you know you can fill out one quick form here on TruckingTruth and apply to several companies at once for paid CDL training? Seriously! The application only takes one minute. You will speak with recruiters today. There is no obligation whatsoever. Learn more and apply here:

Apply For Paid CDL Training