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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.
    Bob Wright

    Spool Gun conversion. How To Do It. Below.


    • #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
      If necessity is the Mother of Invention, I must be the Father of Desperation!

      sigpicJohn Blewett III 10-22-73 to 8-16-07
      Another racing great gone but not to be forgotten.


      • #4
        Thanks guys!