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Thread: Origins of 911 Impact Bumper Regulations

  1. #1
    Senior Member CurtEgerer's Avatar
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    Origins of 911 Impact Bumper Regulations

    There was a change in USA bumper impact regulations between the 1973 and 1974 model years. However, most sports cars, convertibles, and cars with no back seat were exempt from the new regulations until 1975. Both the old (1973) and new (1975) bumper regulations required the car to survive a 5MPH impact with no damage. The regulations had nothing to do with safety or protecting you from injury! It was to reduce repair costs to the insurance industry for minor parking lot type accidents. The old regulation required the test car to simply drive straight into a barrier wall at 5 mph with no damage. The 2 big rubber cushions on the '73 911 could easily meet this standard. But the test procedure changed for the 911 in 1975 and the car now sat stationary while a large pendulum swung down and impacted various points along the bumper replicating a 5MPH impact where the cars were at varying angles to each other. Thus, a continuous ‘impact’ bumper was now required. The 911 was in somewhat of a gray-area of the exemption language because of the rear jump-seats, but had they needed to they could have carried on with the 1973 early 911 design throughout the 1974 model year. But there was no need since the new regulations were planned for years in advance and Porsche had their new impact bumper G-body ready to go and implemented it worldwide for the '74 model year anyway.

    Interestingly, the new test procedure swung the pendulum at a prescribed height of 16-20 inches above the ground surface. There was no height requirement for the barrier wall test in '73 and '74. So I suspect that 1975 may have been the year that started the so-called raised ‘USA ride height’ for the 911.

  2. #2
    Senior Member 767driver's Avatar
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    I believe there was also a minimum headlight height regulation in there as well. It's funny in that in the '74 model year you had 2 versions of the same model within some manufacturers as they came into compliance with the new laws. Early '74 Triumph TR6s had a regular bumper where the later '74 cars had the large, black rubber protrusions added. Early '74 Datsun 260Zs had a slightly extended version of the regular bumpers with small rubber extensions while the late '74 cars had the full-on battering ram (see pic). Porsche probably did the best job of any manufacturer in integrating the new bumper. And remember, back in the day people were updating long hood 911s to the new look!!
    DSCN1219.jpg
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    Last edited by 767driver; 11-20-2011 at 09:13 AM.
    Lee Fishpaw

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    '74 TR6

  3. #3
    Senior Member CurtEgerer's Avatar
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    That's a good point Lee. I've heard people mention the headlight height requirement before. So I did some research on the Motor Vehicle Safety Act of 1966 and everything I can find says that the minimum headlight height (center of light to ground) was and is 22 inches. My '74 is lowered quite a bit and I measured the headlights at 24.5 inches. I no longer believe headlight height had anything to do with ride height for 911s.

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