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Sliding your trailer tandems toward the front or back of the vehicle will primarily 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 very little. To focus only on positioning the trailer tandems, we're going to ignore the minor changes to the weight of the steer axle. It's rarely a factor when deciding where to place your trailer tandems.
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. You can see the holes in the slider rail in the picture to the left (click to enlarge).
The distance between the locking pin holes on the trailer will be the major 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. insight(2); ?>
You scale your truck at a truck stop 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?
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 roughly be:
You scale your truck at a truck stop 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?
In this example, the trailer tandems are overweight (34,000 pounds 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:
So as you can see, this is really simple math. Again, we're assuming the weight won't change on the steer axles for these examples, but in reality, it might change a little. Most of the time, the change in weight of the steer axle will have little or no effect on where you'll put the trailer tandems. The weight on the steering axle is significantly altered by the amount of fuel you have and the position of your 5th wheel, both of which we'll cover soon.
What factor has the greatest affect on how much weight is moved per hole in the tandem slider rail?
Sliding your trailer tandems toward the front or back of the vehicle will primarily change the weight distribution between which sets of axles?
What affect will sliding the trailer tandems forward have on the weight distribution?
You receive a scale ticket and your drive axles are 35,700 and your trailer tandems are 30,600. Based upon a trailer with 4 inch slider rail hole spacings, what is the minimum number of holes you would have to slide the tandems to get the weight legal, and what would the final weights be?
Your trailer has a 6 inch hole spacing in the tandem slider rail and your trailer tandems are 900 pounds overweight. What is the minimum number of holes you will have to slide the tandems to get the tandems within legal limits?
You receive a scale ticket and your drive axles are 32,200 and your trailer tandems are 35,100. Based upon the two most common tandem slider rail hole spacings, what is the minimum number of holes you would have to slide the tandems to get the weight legal, and in which direction?
What are the two most common tandem slider rail hole spacings, and roughly how much weight is transferred per hole?
You receive a scale ticket and your drive axles are 35,400 and your trailer tandems are 31,100. Based upon the two most common tandem slider rail hole spacings, what is the minimum number of holes you would have to slide the tandems to get the weight legal, and in which direction?
You receive a scale ticket and your drive axles are 31,700 and your trailer tandems are 35,100. Based upon a trailer with 6 inch slider rail hole spacings, what is the minimum number of holes you would have to slide the tandems to get the weight legal, and what would the final weights be?
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