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Based on conversation with two of the original GMC engineers, Ralph Merkle and Claude White, who were involved with the air bag patent, memos as well as early sketches, the following is offered.

I have several drawings and memos dated from 09-29-70 through 04-19-72 that deal with the air spring (bag) development. This was brought about since the tooling costs for the hydro-pneumatic spring built by Saginaw originally planned for use in the Motorhome, came in much higher than expected and an alternate solution was desired. A back-up was requested and both Goodyear and Firestone were initially involved in the development and evaluation.

The request was for a free floating air spring with double pistons and the rolling lobe air bag principle instead of a double convoluted type construction used by others in the industry.

Goodyear submitted a drawing dated 01-18-71 which GMC agreed to and issued part number 41089. GMC issued a purchase order and Goodyear delivered the first prototype spring on 03-08-71. With some modifications (shorter and larger in diameter to prevent hot dogging) this spring was used in the production vehicle.

Both Goodyear and Firestone indicated this design was new for this application. Mr. Al Hirtreiter, Chief Engineer of Goodyear Air Suspension Division obtained patent # 3,596,895, dated 08-03-71.

With the documentation I have in hand, I'm quite confident this is the history of the GMC air spring (bag).