Spring Hanger Spacing with the Tandem-Axle Trailer Hanger Kit for Double-Eye Springs # APT9

Updated 11/30/2010 | Published 11/29/2010

Question:

I am using the hanger kit # apt9 with 25 1/4 long springs on 5200lb axles and my question is how far apart should the hanger brackets be spaced?

asked by: Nathan K

Expert Reply:

The distance on center between the spring hanger bolt holes for dual axle setups, with the # APT9 Tandem-Axle Trailer Hanger Kit, should be 29-1/2 inches for double eye springs that measure 25-1/4 inches on center between the spring eyes and for axles that are 3 inches in diameter. This will put your axle spacing somewhere between 33-1/2 and 34 inches.

You will also need to determine the position of the axles before welding the spring hangers into place. The general rule of thumb for double axle trailers is that 60 percent of the trailer weight should be forward of the center between the two axles.

There is a formula that can be used to tell you how far to move the spring hangers when mocking up the trailer.

Once you have all of the parts you will need to determine the correct position for the two axles. This is done by weighing the trailer weight under the wheels and then weighing the tongue weight. Once these weights are determined, you will need to add the two numbers together to get the total weight.

Once the total weight is determined, you need to measure the distance to the center point between the two axles. Now figure the percentage of tongue weight. If it is more than 10 percent, you will need to subtract 10 percent of the total weight of the trailer from the tongue weight. Then, divide that number by the total weight of the trailer. Next, multiply the answer by the on center distance between axle center and center of the coupler. The result will give you the distance that the center line of the axles should be moved forward.

If you have less than 10 percent tongue weight, you will need to move the axles rearward using the following equation. Take 10 percent of total trailer weight and subtract the tongue weight. Then, divide by the total weight. Multiply that by the center line distance between axle center and center of the coupler. The result will be the distance that the center line of the axles should be moved rearward.

expert reply by: Robert G