Where to Position the Trailer Axle?

When positioning a trailer axle or adding an additional axle, the key is to make sure that the axles are located in just the right position so that roughly 10 to 15 percent of the total trailer weight is placed on the tongue. Finding the correct axle location can take some trial and error, so it is best to mock up the locations for all the suspension components until you know everything is in the right spot. When building your trailer, it is best to have the layout of the trailer finalized before placing the axle. This will ensure that the axle is placed in the correct spot to accommodate any permanent weight placed inside the trailer, such as furniture, toolboxes, or shelving. The equations in this article can be used to adjust the trailer's axle location to offer the ideal amount of trailer tongue weight.


Steps to Determine Correct Axle Placement

Axle Placement Infographic Showing Steps and Equations



When Tongue Weight is Less than 10 to 15 Percent of Total Weight


If you find that your trailer's tongue weight is less than 10 to 15 percent of the total trailer weight, then the trailer axle will need to be moved further away from the trailer tongue, closer to the back of the trailer. To know how far back the axle needs to be moved, we want to subtract the trailer's tongue weight from 10 percent of the total weight. Then we will divide this number by the total weight. Then we will multiply this by the distance from the tongue to the axle.


For example, let's say we're building a trailer that has a total weight of 3,500 pounds. When weighed at the wheels and coupler, we find that the weight under the wheels is 3,400 pounds and the tongue weight at the coupler is only 100 pounds. With these weights, the trailer's tongue weight is only 2.9 percent of the total weight. The distance from the front of the trailer coupler to the axle center is 96 inches. Check out the equation below to see how much further back the axle needs to be moved.


Example 1
Example Equations when TW is Less than 10 Percent
For Boat Trailers
When building a boat trailer, the axle is often set back further than on a traditional trailer. On a traditional trailer, the heaviest items are loaded at the front, but with a boat the majority of the weight is at the back of the trailer, meaning the axle needs to be further away from the tongue for the trailer to have the appropriate tongue weight.




When Tongue Weight is Greater than 10 to 15 Percent of Total Weight


If you find that your trailer's tongue weight is greater than 10 to 15 percent of the total trailer weight, then the trailer axle will need to be moved closer to the trailer tongue and the front of the trailer.


Knowing how far forward to move the trailer axle takes an equation very similar the the one mentioned above. However, this time, we will subtract the 10 percent of the total weight from the actual tongue weight. Next, divide by the total trailer weight. Finally, multiply by the distance from the coupler to the trailer axle.


To give an example of this equation, let's say we have another trailer being built that has a total weight of 3,500 pounds. This trailer weighs 2,750 pounds under the wheels and 750 pounds at the end of the tongue. This trailer has a tongue weight that is 21.4 percent of the total trailer weight. The distance from the very front of the trailer, the coupler, to the center of the trailer axle measures 96 inches. Check out the equation below to see how far forward the trailer axle need to be moved.


Example 2
Example Equations when TW is Greater than 10 Percent





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Written by: Victoria B

Updated on: 12/19/2017





Questions and Comments about this Article

Brett J.

I have a trailer frame that fits a 24’ pontoon boat and I have 2 axles with slipper springs and slides that I need to attach to the trailer. How far from the back end of the trailer should I position the rear axle and how much distance should there be between the the front and rear axle? I’m aware that final positioning will be determined by GVWR and mass weight balancing but I need a starting point due to the nature of pontoon boats being heavily weighted in the rear. Is there an industry standard that can be used to for a starting point?

Stu

The article says to know the total weight of the trailer. How do I know this when I am just starting to build and have no idea what it will weight? I also have a trailer that I know the wheels are too far back and want to move them forward to the 60/40 rule. How do I know how much the tongue weight I have or want? Thanks for any help.

Etrailer Expert
Reply from Jon G.

You will need to basically estimate how much it will weigh. The best way to be the most accurate is to calculate how much each of the materials will weigh and then go from there. To transition your current axle to a new position you will need to use the method that we mention in this article. Mocking up the axle position will help with that.

Vince

I have a dual axel enclosed trailer that I have loaded a small pickup, and the rest of my apartment items. before heading out on a long trip, I want to make sure that I have the most ideal weight distribution, or as close to it, as the trailer is already packed up. The total weight of the truck in the trailer is 4400 per the sticker. I pulled the truck into the trailer, with the rear wheels over the center of the axles. After loading the majority of my stuff (minus washer and dryer, I have about 6 feet of empty space behind the truck, leaving little weight on the rear of the trailer. I tried to keep heavier items loaded on the side of the truck, and loaded the bed with stuff, to maximize space. I have a lot of squat on my truck, which I expected to have, but should I move the load a little more to the rear, to take weight off of the tongue, and possibly raise the tongue a little, so as not to have as much squat? Any guidance to help me to this trailer safely would be greatly appreciated.

Etrailer Expert
Reply from Jon G.

For your application you need to be checking your tongue weight. You could be spot on with how you have your cargo sitting or you could be way off - it's much more important to check the weight of your tongue as opposed to eyeballing things. Also compare this to the tongue weight rating listed for your truck and make sure that you aren't exceeding this either.

Akshay

How about for 5th wheel trailer? Is there any changes sir.

Etrailer Expert
Reply from Jon G.

For a 5th wheel trailer you are going to shoot for a tongue weight rating of 20%. I'm not sure where the axle(s) will need to be located for that you so will need to do a mock up of your trailer to figure that out.

Reply from Akshay S.

reese 30047 Hi sir, Is this above 5th wheel can be mounted on chassis by using cross member. If not please suggest 5th wheel of 16000 pound capacity that can be installed in same way as mentioned above.

Etrailer Expert
Reply from Jon G.

@AkshayS The Reese hitch # RP30047 can be mounted on a truck to haul a 5th wheel trailer but you also need the rails so that this hitch can physically connect to your truck. If you let me know the year/make/model of your pickup and what the bed length is I can let you know what you need.

Henry G.

What about for tri-axle boat trailers where do I measure to? I've also read that boat trailers only need to be 5 to 7 percent on the tongue weight?

Etrailer Expert
Reply from Kef G.

You would use the same measurements described above, but you would want the center point to be the center of the middle axle. As for the percentage, there does seem to be a lot of conflicting information. I recommend going with 10% since many sources say 5 - 10% while others say 10 - 15%. Sticking with 10% is the safest bet.

Claro A.

What I want to find out is, Is there a kit that you can raise the height of my alum, car hauler which it is equip with a torsion spring instead of a leaf spring. Modifying it will be expensive specially the labor costs. It’s low that pulling it with my RV.loaded,sometimes it scrapes the pavements when it’s hilly and uneven ground.

Etrailer Expert
Reply from Jon G.

We do have a few axle riser kits that are designed to work with torsion-type axles - I'll just need you to verify what you have by looking at any stickers or labels on the axles. Usually there is one in the middle of the axle that has exact model information. Another thing to check is that you aren't overloading the axles. Check the GVWR (gross vehicle weight rating) of the trailer and make sure you aren't exceeding that, plus you'll want to shoot for a tongue weight that is 10-15% of the loaded trailer for a bumper pull, or about 20% loaded pin weight for a 5th wheel.

Reply from Andrew C.

@ClaroA you could add rollers to the rear of the trailer.

Bill B.

How do you determine the weight of a trailer with out taking it to a scale? I purchased a home made trailer that has been damaged and needs new axels. The current axel is only 8 inches past the center line.

Etrailer Expert
Reply from Chris R.

Taking the trailer up to a local scale is really the only accurate way to get the trailer's overall weight. Are you needing to determine this before replacing the axles?

Bob W.

Confused. Build tandem 16' utility trailer. Need position for center equalizer. Total wt 1500#, wheel wt 1200#. Tongue wt 300#. Distance tongue to old hanger 165 inches. I got ,move forward 16.5" so 149" to tip of tongue. Currently it's just a frame to weigh no decking.

Etrailer Expert
Reply from Chris R.

Jameson does a really nice job of explaining how to determine the right center hanger location on the answer page I linked below. It's really just a matter of making sure you have 60 percent of the trailer's frame length in front of the hanger.

Reply from Brandon F.

@ChrisR Does this "frame length" include the upper deck length of a gooseneck or just the main deck? I have a 41' total length gooseneck (33' main deck, 8' upper deck), both decks are 102" wide with wood floors.

Etrailer Expert
Reply from Jon G.

@BrandonF A gooseneck trailer needs to have about a 20% tongue weight instead of 10-15% tongue weight like what you see with a standard trailer. You will need to do a mock up with your trailer try to get that 20% rating as close as you can.

Lance S.

Just a little confused. if front of trailer to ball is 40 inches and bed length is 100 inches and axile is 3500 pound capacity. where is axile from ball?

Etrailer Expert
Reply from Chris R.

The ideal axle position will depend on the weights you came up with when weighing the trailer - both at the coupler and under the wheels. Once you get those initial weights, you can start to fine tune the axle placement (move forward if tongue weight is too high or rearward if it's too light). There's not a way for me to determine axle distance from hitch ball without those weights.

Reply from Brandon F.

@ChrisR I am building the trailer from ground up and trying to determine axle placement based off hypothetical scenario. What is a good place to start? Does it matter where most of the weight is going to be on the trailer (tiny home on wheels)?

Etrailer Expert
Reply from Jon G.

@BrandonF It does matter where the axles and cargo are, yes. I'm pretty sure they follow this same rule of thumb but I would double check with experts on tiny house building just to be sure. You'll want to take into account not only where all of your appliances and cargo will sit, but also how often you plan on moving. If you're only moving it once then you might be able to get by with a little more freedom as far as where everything goes, but if you plan on moving around a lot I would imagine you would want to try to get all of your cargo to sit in a fairly balanced way so that you don't have to move everything around all of the time when you go to move.



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