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Building a trailer....

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  • Building a trailer....

    I'm putting together a trailer for my buddies airboat, and I have a question or two about tandem axles.

    I need to know how far apart to set the spring hangers. I've done a couple of single axels before, but the tandem has me stumped. Eye-to-eye on the springs is 25 3/16", and eye-to-eye on the tandem coupler is 5 3/4".

    Also is it "better" to have the springs set over the axle, or under? I guess the better question would be what are pro's and con's of either?

    Thanks in advance for any help on this one. I know there are a couple of trailer guys on here, and some of the previous posts have helped a ton already on this project.


  • #2
    The big difference of over or under slung is the trailer height. Over slung will be higher with a small fender and under slung will be lower with a tall fender. Just put the side shakles for the rocker about a 60 degree angle. I will find you a picture..Bob

    Look here:
    Last edited by aametalmaster; 09-03-2008, 10:02 PM.


    • #3
      You need to find the center point of where you will be placing the axle and mount your equalizer hanger there, then simply measure 30 1/2" forward for your front spring hanger and 30 1/2" rearward for the rear hanger.

      Axle placement is generally suggested at the 60% rearward position for a 15% tongue weight, but the center of gravity will be different with the motor on an airboat hanging behind the axles, you may have to play around a bit to find your preferred location to ride correctly. If you have a problem getting the proper axle location let me know and I'll tell you how to do it with a bath scale.

      As Bob has already stated the only real difference in the springs being over or under the axle is about 4 1/2" height difference. In your case I would think you would be better off with the axle above to keep the trailer lower for easier loading and unloading. Dave
      Attached Files


      • #4
        Thanks guys!



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