We ask all drivers to scale each time after loading, even if you have a "light load".
If the facility has a scale- that's perfect, if not- use your EFS card to scale at any truck stop.
Although the trucks are referred to have five axles, when weighing the truck at a truck-stop you will be given three sets of weights - the steer axle, the drive axles as a set, and the trailer tandems as a set. You are not weighing the drive axles or trailer tandem axles individually. They are scaled as a set and the weight limits are described below:
The legal weight limits for each set of axles is:
12,000 Steer axle (but varies by state)
34,000 for the drive axles
34,000 for the trailer tandems
The primary factors which will affect the weight distribution are:
The position of the trailer's tandems
The position of the tractor's 5th wheel
The amount of fuel onboard and the placement of the fuel tanks
The overall weight of the cargo in the trailer and the horizontal (front-to-back) position of its center of gravity
Position Of The Trailer Tandems
Sliding your trailer tandems toward the front or back of the vehicle will change the weight distribution between the tractor's drive axles and the trailer tandems. Sliding the tandems can also affect the weight on the steering axle, but to a small degree.
By sliding the trailer tandems forward, you will put more weight on the trailer tandems and take weight off the tractor's drive axles. Conversely, by sliding the trailer tandems toward the rear of the trailer, you will take weight off the trailer tandems and put more weight onto the tractor's drive axles.
The trailer tandems lock into place with a set of locking pins that slide into holes drilled into the tandem slider rail.
The distance between the locking pin holes on the trailer will be the main factor affecting how much weight is moved per hole. This distance varies between the different trailer manufacturers, and the larger the distance between the holes, the more weight will be shifted with each hole.
The two main hole spacings you'll find are 4 inches and 6 inches. You can estimate that you will move 250 pounds per hole for 4 inch spacing, and 400 pounds per hole for 6 inch spacing. This will help you estimate how many holes you'll have to slide the trailer tandems to move the proper amount of weight necessary in order to get the axle weights legal.
Example 1:
You scale your truck and receive your scale ticket. The slider rail hole spacing is 6 inches which will move 400 pounds of weight per hole, and let's assume the steer axle weight won't change. What would you have to do in order to get your truck legal?
Steer: 11,590
Drives: 34,700
Trailer: 32,100
Gross: 78,390
In this example, the drive axles are overweight (34,000 pound maximum) by 700 pounds. Assuming each hole in the tandem slider rail moves 400 pounds, you would have to slide your trailer tandems toward the front of the truck a minimum of two holes to transfer enough weight from your drive axles to your trailer tandems in order to get your axle weights legal. The end result would be approximately:
Steer: 11,590
Drives: 33,900
Trailer: 32,900
Gross: 78,390
Steer: remains unchanged for this example
Drives: 34,700 - 800 (2 holes x 400 pounds each) = 33,900
Trailer: 32,100 + 800 (2 holes x 400 pounds each) = 32,900
Gross: Remains the same
Example 2:
You scale your truck at a truckstop and receive your scale ticket. The slider rail hole spacing is 4 inches which will move 250 pounds of weight per hole, and let's assume the steer axle weight won't change. What would you have to do in order to get your truck legal?
Steer: 11,320
Drives: 31,300
Trailer: 35,050
Gross: 77,670
In this example, the trailer tandems are overweight (34,000 pound maximum) by 1,050 pounds. Assuming each hole in the tandem slider rail moves 250 pounds, you would have to slide your trailer tandems toward the rear of the truck a minimum of five holes to transfer enough weight from your trailer tandems to your drive axles in order to get your axle weights legal. The end result would be approximately:
Steer: 11,320
Drives: 32,550
Trailer: 33,800
Gross: 77,670
Steer: remains unchanged for this example
Drives: 31,300 + 1,250 (5 holes x 250 pounds each) = 32,550
Trailer: 35,050 - 1,250 (5 holes x 250 pounds each) = 33,800
Gross: Remains the same
The Weight Of Fuel
The weight on the steering axle is significantly altered by the amount of fuel you have and the position of your 5th wheel.
The precise weight of diesel fuel will vary based on temperature and humidity, but is generally around 7.25-7.5 pounds per gallon. So the safest bet is to use 8 pounds per gallon as the number for your calculations.
Sliding The 5th Wheel
Sliding the 5th wheel will change the weight distribution almost exclusively between the steer axle and the drive axles. The trailer tandems will see little or no effect from sliding the 5th wheel. If you slide the 5th wheel toward the nose of the tractor you will increase the weight on the steer axle and take weight off the drive axles. If you move the 5th wheel toward the rear of the tractor, you will increase the weight on the drive axles and decrease the weight on the steer axle.
Set It And Forget It
Unlike the trailer tandems , sliding the 5th wheel is something you will rarely do, if ever. The reason is simple - there's an ideal place to set the 5th wheel based on the tractor and trailer combination you're using and there's really no need to move it once it's set properly.
The best way to make sure the 5th wheel is set properly is to scale the truck with a minimum of 1/2 tank of fuel, a very heavy load, and the trailer tandems set so that the drive tires are as close to 34,000 pounds as possible. Under those circumstances, you will want the 5th wheel positioned so that the steer tires are as close to 12,000 pounds as possible without going over, and the trailer tandems as close to 34,000 as possible. Once you get it set, you can leave it alone after that.
Source: HERE