Tandem Setting Formula

I am a scale house clerk, and I would like to provide some additional info here. First, the limit on the front axle is set by the ratings on the tractor, which can be found on the edge of the driver's door or the mating area of the body of the truck. You cannot exceed the rated weight of the front axle. Every truck is different so check your rig, I have seen some rated for 13,500 and they usually are loaded to over 79,500, with weight on their steers around 12,800. This ensures they will be able to keep the weight of their drive and trailer tandems below 34,000.

Some drivers come in with fixed 5th wheels, set to 10,200. That limits the load weight they can carry, by the amount less than 12,000lbs. The 5th wheel is important when distributing weight on your truck.

We ship heavy loads and, no matter how good a loader is, if you are carrying 79,000 or more, it is necessary to put as much weight as possible on the front axle, in order to adjust the load so the drive and the trailer are less than 34,000. Keep in mind all the weight, including you and your fuel, and we generally recommend drivers come in to pick up their loads with 1/2 tank of fuel.

As far as the trailer tandems go, the hole spacing will determine how much weight is moved. Generally, the closer the axle is to the center of the load, the more weight will be moved. I use an average weight per hole and if the driver doesn't know their spacing or what hole they are on, I can go out and look and help them adjsut their weights to get them legal. Some drivers come light on the steer, and we also have to move the 5th wheel to get them legal. We have an onn site scale, and I was a driver, so I am very familiar with weight distribution. Sometimes I have to send a load back to the door for rework, but that is rare.

I have seen hole spacings that only move 180 per hole and others that move 625. Get to know what your hole spacing shifts. When you get scaled mark the position of you pin before you move you axle. If your trailer is heavier than your drive by 1000lbs, the move 2 or 3 or 4 holes and reweigh. See how much you increased or reduced the weight on each axle (it may be different) and divide my the number of holes you moved. That is the average weight you shift per hole on that trailer.

Get to know your truck and trailer. I hope you all get to our place sometime. I always enjoy talking to drivers.

Larry

 

Things weren't that simple when this discussion was posted 9 years ago, and they aren't any simpler today. I spent most of my driving career at a company with a fixed 5th wheel, but since I had a cabover with a setback steer, my front axle was pushing 12,000 even empty. It really depends on how evenly the trailer is loaded, and where the center of gravity is. If you have a 53' trailer, and your load only goes back to the 45' line, you'll need to bring your tandems forward. Also, 53' and 57' trailers should really almost never (and on 57' trailer, probably absolutely never) have their tandems slid all the way back. Pay attention to the axle-distance laws especially in California, or you'll find yourself overlength on a PERFECTLY balanced load, then have to spend several hours in a hot trailer moving freight forward by hand....

I used to get a regular load at an aluminum mill; it was 5 equal-sized coils, each weighing 9500 lbs, which would lay flat on the floor. They would always load 2 in the nose, then block them in with 2x4 pieces nailed to the floor. Then they would ask the driver to MARK where they were going to nail the forward 2x4 for the rear 3 coils. I ended up working the weight load out on paper with the tandems set at the 42' mark (which was what we needed to be in that area), and did calculations for both a 48' and a 53', then gave it to my dispatcher. They started giving out my calculations to other drivers; they may still be using it for all I know...

 

This is the 'tool' I keep handy for when I actually DO need to slide my axles into a position OTHER than full forward or full rearward....

When I bought it, I had to go to Lowe's for the eye bolt, nuts, washers and thread lock....

 

Great idea. If I'm understanding correctly you pop that in to the pin-hole just past where you want to stop and it stops the tandems from sliding any further?

 

The simplest formula is,,
If your to heavy on the drives,,, slide your seat forward a couple of notches.

 

Yes... say the math (and I HATE MATH!) says to slide axles rear by 7 holes.... put it in hole 8, release the pins and pull the truck forward. Reset the pins and rock the truck back to lock the pins in place. Then you'll be able to pull the "thimble" out. The eye bolt makes it easier.