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3 Key Measurements Are a Must

FellingAFrameGooseneckCloseup3-Key Measurements,

are a must when choosing an A-Frame Gooseneck coupler hitch style.


You’ve decided to buy a trailer and want one with an A-Frame Gooseneck Coupler. The choice of an A-Frame Gooseneck coupler over a bumper pull will gain you additional stability. With the tongue weight focused over the tow vehicle’s rear axle vs. the back of the frame, the potential for the trailer to sway is reduced. But before you seal the deal, make sure that the trailer is compatible with your truck (tow vehicle.) Choosing a trailer that doesn’t have the right swing clearance can lead to damage to the trailer and even worse, damage to your truck.

Get a Quote for Your Gooseneck Trailer

Here at Felling Trailers, Inc., we recommend using a Swing Clearance Worksheet (see below), this will help to determine the proper clearance needed for the power unit (tow vehicle) used or intended to be used. The Felling FT-20-2LPAFrameGooseneckSwing Clearance Worksheet allows us to optimize the gooseneck length allowing the maximum needed for weight transfer to the steer axle and/or maximum useable deck length allowable by law. Simply fill in the blanks pertaining to the configuration of the Truck or Tractor. In most cases, the minimum swing clearance required will be 4 inches more than the suggested diagonal measurement on the worksheet.

Here is a breakdown of the measurements that you will need;

Felling's A-Frame Style Gooseneck Swing Clearance










Swing Clearance Worksheet for A-Frame Gooseneck – Download Worksheet

Accurate measurements are critical to prevent damage to the trailer and tow vehicle when being towed.

The A-Frame Gooseneck option is most commonly used on Deck-Over Tag and Drop-Deck Lines.

Talk to our Trailer Experts to ensure that your tow vehicle and gooseneck trailer are the right match.

Looking for information on Semi Tractor-Trailer (Gooseneck) Swing Clearance Click Here.






  1. Doing the math on a trailer is really important. You don’t want to destroy your back end if you take a turn too sharp. I’ve seen it happen and the repair bill does not put a smile on anyone’s face other than the technician. Great post for beginners!

  2. What is the diameter of the neck wanting to switch to 5th wheel but need to know Id and od of the neck

    • Felling Trailers says

      Hello Mark,

      8’ is standard but we can design custom goosenecks for different swing clearances if needed.Feel free to contact our Sales Team for further information.

      Thanks, Felling Trailers

  3. What if u have a truck with a lift kit on it

    • Felling Trailers says

      Hello Mike,

      To find your needed Swing Clearance for your truck, lift kit or no lift kit, you will need to know: what the Ball/Pin Height is on your truck (see diagram letter B). Next find the Box Side Height of the tuck (see diagram letter C), then the Box Height(see diagram D).

      Thanks for the question,
      Felling Trailers

  4. What is the clearance/diameter around the ball/ hitch area. A gooseneck hitch is already installed in my new truck but, looking to add “pack rat” style drawer unit tool boxes on each side. So, with 48” bed width and a 20” tool box on each side(next to the fender well). Is that enough clearance for a travel trailer goose neck hitch. Thanks

    • Felling Trailers says

      Hello Bart,

      If we understand the measurements supplied correctly, this will only leave 8” of space between the boxes. The coupler itself is 8” wide so there would not be enough room.

      Thank you for the question,
      Felling Trailers

  5. Donald Sutherlamd says

    Ive got plenty of clearance for swing & bed height. The landing gear has about 6″ to 8″ off the ground when fully retracted. I know some entrences to fueling stations have dips & inclines which can & do cause the ass end of trailers to drag. My concern is the landing gear itself. Can I drop the goose neck down to give more ground clearance on the landing gear & if so does that not change or shift the load weight to much to the rear axles ?

    • Felling Trailers says

      Hello Donald,

      The most important this about towing a trailer is how level the deck is when loaded, the deck should be 2” – 3” higher in the front than the rear for best towing results. This is adjusted by raising or lowering the gooseneck coupler. We state the coupler height on all our quotes and orders so the customer can be aware before ordering if the stated height is not going to work a custom height can be ordered. The beavertail and ramps are designed to pivot and clear the ground at this slight upward deck angle if the front is raised too much the ramp support legs will contact the ground before rotating completely. The concern about the jack leg(s) ground clearance should be based on the proper deck loaded angle first, then if need be, the foot of the jack legs should be modified for additional ground clearance.

      Felling Trailers

  6. I am trying to purchase a gooseneck coupler and install myself on my own trailer. Will you sale a pre fabricated coupler?

  7. Gordon Schmill says

    What determines the size of the I beam or channel iron of the neck? Most trailers are made of 12 inch but I have seem some with 10 or 8 inch. Is there a formula? I have a 16 foot flatbed trailer made out of a trailer house frame (I believe 12 I beam) with two 7,000 lb torsion axles. Its a bumper pull but I’d like to convert it to a gooseneck. Suggestions?

    • Felling Trailers says

      Hello Gordon,

      In order to give the best suggestion, we would need to see the actual trailer, have our Team review its structure, and then give a suggestion of how to convert from a bumper pull to a gooseneck if feasible. If you would like to schedule a time to do so you may contact our Parts & Service Department at 1-866-335-5464 or email at parts2@fellingcom. If this is not an option due to your location we would suggest contacting one of your local welding/fabrication shops.

      Thanks much,
      Felling Trailers

  8. Howdy guys,
    I am installing a 8′ W x 10′ L flatbed on my 2008 3500 Dodge dually.
    The goose neck hitch is approx 57 or 58″ from the cab, centered over the axle.
    I need to cut the corners of the flatbed at 45 degrees for turning sharply.
    I have a standard Hallmark enclosed 40′ gooseneck.
    My current rear bumper sticks out to 9′. No turn clearance issues.
    There will be no sideboard height issues. Deck height.
    I would do the fit empirically,…but the truck and Hallmark are not near each other right now.
    Figuring an equilatteral triangle length on the A and B legs, what is a good number for leg C,..the hypotinuse?
    Thanks in advance!

    • Good afternoon Chris,

      With the information provided its hard to give you a clear answer. You can start with this swing clearance guide, or if there is a dealer near you maybe they could help.

      Thank You
      Felling Trailers

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