Shifting Trailer Weight?

Amen!
........

 

I'm a little curious as to how, after 5 years a trucker, you are just now asking about weight distribution on axles!?

Here are the basics...everyone so far has stated the effects of sliding the tandems, however nobody answered the question.

Think of the trailer and the axle (tandems) as a teeter-totter on a playground. When you slide your tandems forward or back, you are moving the plank from center to either direction of the lever. How the trailer is set up (each manufacturer is a bit different) the spacing of the holes will establish the amount of weight being transferred. Wabash uses 5.5 inches between center of the hole, Great Dane uses 5 inches from center, Pines uses 4.75 inches to center. This difference of less than one inch to center, accounts for the variance of 300 to 450 pounds per hole.

When sliding your tandems, keep in mind how you are going to tell yourself which direction to move. I taught all my students to "move the trailer--not the tandems". Which is actually correct, as the wheels/tires are locked in place and the trailer is the part sliding on the tandem unit.

To move weight from rear to front....slide the trailer back.
To move weight from front to rear....slide the trailer forward.

The direction you want weight to move is the opposite direction you move the trailer.

As one poster stated...be careful when moving the tandems, you need to keep Bridge Law in mind. CA is 40', FL 41'...all states length limits are in the Atlas, a great tool every trucker should have. And the regulation information with Rand-McNally is updated every two years, on the odd year, the even year is identical to the previous years publication.

One last point...if you move 350 pounds per hole, you slide tandems 3 holes, you have effected 1050 pounds...from one end and at the same time you have added to the other end. Which is why another poster mentioned the fact you didn't state the weights on the drives and the steers...all these factors need to be noted and adjusted.

Good luck driver!

 

What you first need to identify is how many pounds will be transferred for each hole you slide the trailer tandems.
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Next when you have your first weigh printout, take the trailer tandem weight and subtract the drive tandem weight. Finally, divide by 2 times the amount that each hole will move. The answer is how many holes you increase the trailer wheelbase.
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EXAMPLE 1: Each hole moves 250 pounds. Weight on the trailer tandems is 28,000 and weight on the drive tandems is 24,000. Note: the trailer tandems are heavier than the drive tandems.
.So 28,000 - 24,000 = 4,000
4,000 / 500 [2 times 250] = 8.
.Therefore increase the trailer wheelbase 8 holes.
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EXAMPLE 2: Each hole moves 400 pounds. Weight on the trailer tandems is 27,000 and weight on the drive tandems is 30,000. Note: the drive tandems are heavier than the trailer tandems.
.So 27,000 - 30,000 = -3,000.
-3,000 / 800 = -3.75. The answer is a negative number. Since you cannot increase the trailer wheelbase a negative amount, you shorten the trailer wheelbase. Because you cannot move a partial hole round to the next whole number. -3.75 is rounded to -4.
.Therefore DECREASE the trailer wheelbase 4 holes.
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Using this formula will equalize the weight between the trailer tandems and the drive tandems. One calculation, slide the tandems once and you are done.

 

Here's my rule of thumb:

1. Unless the load is really light, like 38k or less, make sure they load it in the first 48ft of the trailer. This will help you to stay within the bridge law while still maintaining legal tandem weights.

2. Set the fifth wheel so it is centered between the drive axles. You'll most likely be able to leave it set there and never touch it again.

3. Set the trailer tandems so the the rear set of tires just barely protrudes beyond the end of the load (six inches or so). If the load is forward of 48ft, you should be good for bridge law.

Weigh the truck. If your steers are good (11,500 or so with a full tank of fuel). Then you likely never have to worry about moving the fifth wheel.

The weight on the drives and tandems should be pretty even. The overhang on a 53 footer doesn't seem to add much weight to the tandems.

I've done it this way for a long time now and rarely visit a Cat scale unless I know for certain the load is close to gross. If a shipper has a scale, I might double check my axle weights... it's always legal.

 

I'll bet the OP never asks anything again !!!!!

 

Make sure your drives and tandems are at the ends of the load and that the load is evenly distributed, like this, and you'll probably never have to see the weighmaster in person.

 

I fixed it for you!

 

This is by far one of the best explanations I have read. My school did not even explain it like that.

Thanks!

R/

Frat