Tractor Trailer Axle Weights And Distance And How To Adjust Them

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(Last Updated On: November 4, 2017)

This week I’ll discuss adjusting the weight on your tractor and trailer axles. You will find yourself adjusting your axles frequently and since it’s your responsibility to make sure your weights are legal, this is important to understand.

One tip I can give is that with light loads it’s a good idea to slide the trailer axles all the way forward. It makes it a lot easier on turns. It’s not required. It’s just a matter of preference. 

 

Making Sure Your Axle Weights Are Legal

 

When you pick up a heavy load, the best advice I can give you is to not trust the weight the customer puts on the Bill of Lading. Here is an example of why you shouldn’t.

I picked up scales1a load someplace in the middle of nowhere Kansas once. The nearest truck stop with a scale was 35 miles away. When I pulled away from the dock and started down the road the truck was struggling more than I had ever seen it do before as far as picking up speed and getting up some of the hills. The load felt really heavy, certainly a lot heavier than the 35,000 pounds that the shipper had written on the BOL.

I finally got to the truck stop, scaled the load and found my gross weight to be 85,000 pounds. That means, since my empty truck and trailer weighed 35,000, give or take a few hundred, the load was actually a 50,000-pound load, 15,000 pounds more than what was on the BOL.

I had to take the load back and have some of the freight removed, even though the shipper was upset about doing it, but they load a lot of trucks out there every day so I’m pretty sure they knew what they did and hoped I was a new driver who wouldn’t come back. But, the driver is responsible for the legality of the weight so there was no way I was going to take that load overweight.

Some shippers have their own scale but I wouldn’t trust it completely. Who knows how long it’s been since it’s been checked or how accurate it is. You really want to use a certified scale at a truck stop.

To be on the safe side, anything you pick up that says 35,000 pounds or more, scale it. As you gain experience you will be able to tell by the feel if you are heavy or not but sometimes a heavy load is loaded so well it feels lighter than it actually is and a light load may be loaded in such a way that it feels a lot heavier than it actually is. I know of one shipper I went to that made a 25,000 lb load feel like 50,000.

Once you scale, you may need to adjust the axles on the trailer to get your weights correct. Here is what the maximum legal weights are for your axles.:

  • Steer axles: 12,000Axle slide3
  • Drive axles (axles on the back of the tractor): 34,000
  • Trailer axles: 34,000

Our maximum gross weight allowed is 80,000 pounds.

The trailer has axles that can be slid. Look under the trailer around the wheels you will see the locking pins that project through the trailer rails directly under the floor of the trailer. On the driver side, near the front wheels of the trailer, you will see either a handle or air valve to pull which will pull those pins in so the axles can be slid. Once you do that it’s time to get in the truck and slide them.

Ideally, you want your drive axles and trailer axles to weigh about the same for better handling.

 

Sliding The Axles

 

Here are how the weights change when sliding the axles. 

If you slide the trailer axles back toward the rear this will make the trailer axles lighter while adding weight to the tractor drive axles. Slide them forward, more weight is added to the trailer and less to the tractor.

Axles slide1So, the next question is how far to slide them, one way or the other.

The rails on the trailer have a line of holes. You will notice some trailers have the holes close, others have them spread farther apart. If you don’t have two different kinds of trailers to compare, measure the distance between the holes with your fingers. If your fingers are a few inches apart, those are the “close” holes, as I called them. If you have to spread your fingers really wide, those are the “far” holes.

If you look at the two images you can see the difference between the “close” and “far” holes. See the rail guide underneath the holes? In the image just above this paragraph, you can see the guide covers the distance of two holes. In the bottom image, it can fit in a space between two holes.

The reason this is important is that the distance between the holes determines how much weight will be shifted with each hole. The “close” holes will be approximately 250-350 pounds per hole, depending on how the freight is loaded. The “far” holes will adjust approximately 450-550 pounds per hole.

 

Axles slide2So let’s use an example.

The scale ticket gives us a reading as follows :

  • Steer: 12,000
  • Drive: 35,000
  • Trailer: 33,000

We are 1,000 pounds over on the drive axles but 1,000 pounds light on the trailer. This means we have to add weight to the trailer and take it off of the drives. So let’s do it.

Make sure to lock your trailer brakes before sliding. If you have an air valve to release the pins you won’t be able to pull it unless the trailer brakes are already locked.

The holes on the trailer are “close” holes. I start by figuring it will be about 250 pounds per hole. I want to get the drive axles at or under 34,000. So, 250 lbs. x 4 = 1,000 lbs. 

I want to slide the trailer axles forward 4 holes. Make sure after sliding you lock the pins back in the holes. If you have a handle you will need to release the handle. If you have an air valve, you will push the trailer air valve from in the cab of your tractor. After locking the pins back make sure to rock the trailer back and forth to secure the pins the get out and look to make sure all of them are locked in place. If you used the air release valve in the cab to lock the pins again, make sure you pull the valve back out to lock the trailer before rocking it.

The new scale ticket should look something like this:

ScaleTicket1

 

If you have the “far” holes you would slide two holes, 500 lb x 2= 1,000 lb.

The “far”, “close” hole term is my personal term, just to let you know.

When sliding you will not have to move the truck very far, it’s just a matter of inches. At first, it will be a little difficult but with practice and time you will be able to figure it out and it will become much easier and quicker. You could ask someone who is close by to let you know when the pins are lined up.

Another option is to get yourself a “stop bar” which you can place in the holes in front or behind of the holes you want the axles to go into. This will stop your axles where you want them to be.

It’s really not as difficult to adjust weight as it may appear. Ask your trainer to let you practice, even with lighter loads.

 

Adjusting The Fifth Wheel

 

Another way to adjust axle weight is by sliding the fifth wheel, the place the trailer attaches to the tractor. Some tractors have this option, some don’t. It depends on the company you work for. 

Personally, I hated doing this. Each truck I would get I would find the “sweet spot” for the fifth wheel where the need for this rarely came up. Each truck had a different fifth wheel rail configuration so none of the sweet spots were the same.

fifthwheel 1However, sometimes the trailer is loaded in such a way that your gross weight is legal, your trailer weight is barely legal but you can’t add any more to that, but your drive axles are overweight. Beer loads were good for this. This is when your fifth wheel comes into play. Adjusting it shifts weight between your drive axles and the steer axle. It will have little to no effect on the trailer axles.

There will either be a handle at the fifth wheel to pull to release the lock pins or you may be lucky and have an air release switch in your tractor. There aren’t that many holes in the fifth wheel rail but it can make a pretty big difference in the weights. You will want to lower the landing gear to remove some of the weight from the fifth wheel. If you don’t it is REALLY hard to slide and could cause some damage.

Sliding the fifth wheel forward will add weight to the steer axles. Sliding it toward the rear will add weight to the drive axles. It can seem confusing because one would think that sliding it forward would put more of the trailer weight on the drive axles since more of the nose of the trailer is across them, but it actually moves the weight to the steer axles.

When you get a truck, experiment with the first few heavy loads you get to find the sweet spot for the fifth wheel. If you aren’t having any problems with the steer axles being over 12,000 lbs and you can get your drive axles legal just with moving the trailer axles, your fifth wheel is probably fine where it is. If you find yourself having to constantly adjust it, work on finding the ideal location because the need to adjust it should happen rarely once you have it set there.

 

Bridge Laws And Axle Distance

BridegLaw1

 

This is another reason you will have to adjust your trailer axles. It can get really tricky if you have a heavy load that requires your axles to be a certain distance back but it will make the axle distance an illegal distance in one or more of the states you’ll be traveling through since each state has its own bridge law regulation.

When that situation arises you will have to contact your dispatch to find out how they want you to handle it.

What this is about is that states put a limit on how far back your trailer axles can be on a 53-foot trailer. The measurements are from the kingpin to some point on your trailer tandems.

For example, some states may measure from the kingpin to the center of the axle GROUP. Others may measure from the kingpin to the center of the REAR axle. Some have no limit. It’s the driver’s responsibility to know the law for each state and a trucker’s atlas gives you a good reference guide. It has all the information you need regarding weight and distance in the front section. You can ask your company if they have a chart you can have. Here is a link that can give you an idea of how this works.

Make sure to ask your trainer to explain the laws. It is very important.


I can’t cover every scenario here but it is very important for a driver to know this. Make sure you have your trainer work with you on all of this. Have the trainer show you where they have their fifth wheel set and if the truck you get has the same setup as their truck you can set it before you leave on your first trip. You will need to be hooked to a trailer to slide the fifth wheel.

All of this can sound pretty daunting but it won’t take long before you understand it.

 

Feel free to leave comments or further suggestions.

Next time, the article will discuss a very important issue, driving with heavy loads.

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29 Thoughts to “Tractor Trailer Axle Weights And Distance And How To Adjust Them”

  1. jeff

    One big mistake that truck drivers do is to fail to calculate the actual weight of the trailer. The weight may seem insignificant in comparison to the trailer but this really helps in determining whether the equipment will be pushing the load past the tow vehicle’s capacity. I guess this is something every new driver needs to be keen about.

    1. Dennis

      That’s a good point. Different model trailers weigh more or less than others. It helps to learn the trailers your company uses and find out the empty weight of your tractor and trailer combined. Tractors can vary too based on model and accessories.

      It pays to ask someone who would know about those empty weights.

      1. wayne

        Reading this article and all the comments, I now understand why trucking is not an easy job as most people like to assume.

        There is so much a trucker is supposed to know and I believe mistakes will always be made in the course of learning.

        1. Dennis

          This is why I am trying to give people a place they can learn about the business before jumping in because they think it’s such a glamorous job. It’s far from it.

  2. Wilson

    Different states and their different requirements can be real pain for the rookies doing all 48. But as they say, put your time in so you can get a dedicated route and you wont have so much to remember.

    1. Dennis

      True. I do think that since the trucking industry falls under the control of the US DOT there should be fixed regulations for all 48 states. As it is now, not only do we have to know Federal Regulations, we have to know all state’s regulations. It’s a mess.

      1. Johnny 5

        You’re right, it’s a mess. No industry is perfect though so you have to learn to do your best with what you have. I really do wish they could simplify it though.

      2. malcolm

        Such a mess, I agree. How much harder is it for a rookie who is just trying out new stuff about truck driving? Not only have you to start grasping things fast but also memorizing Federal and state regulations.

        Not easy at all.

        1. Dennis

          I was never able to begin to get into state regulations with trainees.

    2. luke

      True Wilson; it can be very challenging for rookies and as you say, getting a dedicated route seems like the best way out. It takes hard work and patience to be a good truck driver and one shouldn’t be too worried of making mistakes in the beginning.

  3. Ryan

    I know it’s chain of custody issue, but I still wish the company doing the loading had to bear at least some of the responsibility here. It’s only fair.

    1. Dennis

      I believe there are attempts to make everyone involved in the load, shipper, driver, trucking company and receiver take their share of responsibility. We’ll see where that goes.

      Personally, I think the idea of the driver being the ONLY one responsible is unfair because if a shipper doesn’t want to re-do a load to make it balance out better, or whatever, as long as they weights are legal they won’t adjust anything. Like that shipper in NJ. I asked several people if they would brace the load but they all said no. Being a brand new driver then I was a bit scared to refuse to run it. Today, I would refuse. Also, the trucking company should bear some of the responsibility if something were to happen with that load since they told me to run it as-is since it was a legal weight.

      It’s also unfair since on a drop and hook load the driver can’t see inside at how the load is stacked.

      1. djanana

        It is really unfair to heap all the blame on the driver. The shippers also seem to always take advantage of new drivers because they assume they will not question and unfortunately, at times they do fall for the trap. I believe that the trucking company should bear the biggest responsibility, nonetheless.

        1. Dennis

          You are correct about hoping they get a new driver who will be too afraid to speak up or doesn’t know any better and just take the load. I would tell my trainees that the only person who will look out for them is themselves, so stand up for yourself, but be courteous while do so.

  4. jeff

    Reading this, I get the feeling that customers may have the urge to understate the weight especially when the truck driver is new. It must have been really annoying to have to drive back after 35 miles or so; I’d have been seething with rage. One thing I have picked from this is that, a truck driver had to always remain level-headed and take things as they come. Is it possible to always counter check the weight at the shipper’s?

    1. Dennis

      I believe the weight of the load is part of the billing process for the trucking company so it would benefit a shipper to understate it.

      I wasn’t all too happy about returning but you can’t take it out on the customer. That could cost your job. I used to write novelettes to the DM to blow off the steam. lol

      Some shippers do have their own scales but if they are trying to cheat the weight their scale most likely isn’t accurate. Even if they are, many places still want a copy of a scale ticket from a certified scale such as a CAT scale, before they’ll adjust the load. Don’t even ask me why they do that if they have their own scale, but it does say a lot about the customer’s scale, doesn’t it?

  5. malcolm

    My good friend Brian has his thoughts inclined to the fact that his job will only be to get a truck from point A to B. I have severally tried to impress upon him that there is a lot that comes with being a truck driver and having attended training is just the beginning of a somewhat long but interesting journey. I know of several friends who started out as truck drivers and 10 years down the line, their stories are different; they own several trucks of their own. My point is this, it does not matter where you start. Get everything right from the beginning and always ensure your weights are legal. I loved this read.

    1. Dennis

      True. If you take your time, do everything right initially, you can save yourself a lot of wasted time later on.

  6. djanana

    It must have felt really bad for you as you were returning the freight back for some of it to be offloaded. At the same time, it was such a waste of time and manpower. I like the way you are encouraging new truck drivers that over time, it gets much easier to grasp some things.

    1. Dennis

      It is a waste of time especially since it is a shipper that my company dealt with all the time. They know how that shipper works.

      In general, the first year is the most difficult, both in learning the ins and outs of the job and adjusting to the lifestyle. If you can get through the first year you should be okay, generally speaking. I can’t say that holds true for everyone.

      As you start grasping things they start to become automatic and as a result take less time to do. Just figure out a system that is good for you and stick with that system. Don’t keep changing things up. If you follow the same routine all the time it decreases the chances of making mistakes.

  7. Broom

    It must be annoying to have shippers who try to fool us because we are ‘only’ drivers. I guess we should always be ready to make more than one trip in such situation. Have you ever had a case where the shipper insisted that you only did one trip despite the excessive loads?

    1. Dennis

      Yes I have, but I told them, and my company, that I was not going to run an illegal load. The shipper said if I wouldn’t run it they would have to find someone else who would and I told them, in a nice way, that’s what they would need to do then. My company backed me up on it.

      Eventually, grudgingly, the shipper removed some of the freight.

      1. Broom

        I’m glad it worked out for you. This kind of communication skill is hard to pass from teachers, so we will need to learn by practice. If it were me, I would probably lose my patience easily due to exhaustion and illogical demands.

        1. Dennis

          It can get extremely aggravating at times but the best thing to do is just keep quiet, go to the truck, let your DM know what’s going on, and cool off a bit.

  8. Joe

    This sounds really complicated. I didn’t realize the state laws were different. If the state law is different from the one that you just left, do you have to pull over and adjust it all again?

    1. Dennis

      You want to make sure everything is good to go for all the states you’re going through before you get started.

      I guess, if you wanted to, you could re-adjust them along the way, but make sure that will be possible before you leave the shipper.

      Sometimes you may have a load with more than one delivery stop so after each one you could adjust them again (move the axles forward) to make up for the weight that was taken off.

  9. Caden

    This is filled with so much useful information. Thanks for writing this piece. I’m wondering, though, what happens if you do get placed with a load that is heavier than what is stated on the papers and you end up getting pulled into a weigh station for a surprise inspection? Does the driver get cited for this, or will it become the companies responsibility?

    1. Dennis

      If the company didn’t authorize you to take the load as-is the ticket will be the driver’s responsibility.

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