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Thread: 911 shoulder harness installation

  1. #1
    Rick Cabell

    911 shoulder harness installation

    I am in the prossess of putting shoulder harnesses in my 71 and don't want to drill any holes in the car. The setup that i have seen and like is the 2 straps going through the 2 headrest posts and then crossing and then attaching to the factory tapped holes where the rear seat belts attached. where the straps crossed they were anchored together by a steel clip kinda like a childs car seat uses. what would be the proper anchor to screw into the rear seat holes? Any paticular type of harness that seems to be "made to fit" in these early cars?

  2. #2
    Hi Rick,
    I see you're starting to get this baby ready for some serious roadwork.

    You can attach the shoulder harness to the rear seat belt anchors. Make sure the straps are long enough for this distance. An eyebolt-type anchor would probably work best here. The thread size is SAE (1/2" I think). However, if you choose this location, you should also install a harness bar (or roll bar) to reduce the belt angle from your shoulders down to the belt anchors, this to avoid spinal compression injuries in the event of a frontal collision. I've also seen anchors installed on the rear window shelf. This location is near shoulder height avoiding the need for a harness bar. Crossing the shoulder belts behind the seat is a good idea to prevent the harness from separating from the shoulders.

    Take care,

  3. #3
    Chuck Miller

    911 shoulder harness installation

    Sherwood's da-man, but the thread size is 7/16"/ 20 NF
    for the seat belt anchors.

  4. #4
    Thanks for the clarification. No wonder my impact gun couldn't get that 1/2" bolt in there.

  5. #5
    Rick Cabell
    Thanks guys,Is it not 12mm fine thread?? (Metric)

  6. #6
    Chuck Miller

    : 911 shoulder harness installation

    I belive the U.S. mandated safety standard specs in the 60's became the international STANDARD.

  7. #7
    Hi Rick,

    Here's the info I promised about the Willans harness that crossed over in the back, which you liked in my blue '72S in Vegas:

    Willans Club 4 x 4 harness in 3" blue, L.H. seat (standard 54" long shoulder)

    Contact Stockbridge racing, England Tel: 01264 810712

    Randy W

  8. #8
    Rick Cabell
    Thanks Randy, I still love your seat!!!

  9. #9
    An alternative to crossing the shoulder straps is to use an "H" style harness, which has a cross-strap behind the seat to prevent spreading of the straps if your seat is not the type with guide holes cut in it for the harnesses. A harness bar with guides will also prevent this. This should also be combined with a quick-release sternum strap in the front to serve the same purpose. If the straps can slip down over your shoulders, they aren't going to restrain you in an accident.

    Rick, if you lead the shoulder straps inside the headrest posts, I think you will find that they tend to abrade your neck pretty badly. You will also want to invest in a pair of harness pads to prevent this. They're a lot softer than the bare webbing.

    I can confirm that the seatbelt anchor points are all indeed 7/16" SAE, not metric thread. Any standard forged eyebolt seatbelt anchor from US sources will work in them.


  10. #10
    Rick Cabell
    Everyones advice is well taken.Seems I have a couple good options. I thought the harness guide bar was for proper belt spacing. I never thought of spine compression. Very important!!!! Makes perfect sence.

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