Tar Wheels…Landmarks of the American automobile…the all-steel top

by Bob Blake

The automobile has crossed many significant milestones in its evolution. Innovations such as shatter-proof glass, hydraulic brakes, improved tires, and mandatory seatbelts have vastly improved crash survival. The marvels of air conditioning, sound deadening, GPS devices, power steering and plush seating have made automobile travel enjoyable.

An often-overlooked landmark in automobile construction is the advent of the all-steel top. Before 1935, sedans and closed automobiles had a steel chassis and a body made of wood and metal. The top, however, was a composite of hardwood, wire mesh, and fabric. They often leaked, squeaked, and added nothing to the integrity of the body shell. Manufacturers were clever enough, however, to blend this composite into the design, so it appeared as one piece – but it wasn’t! 

Why not an all-steel body? The steel mills were unable to roll a single piece of metal large enough for a one-piece top. In 1932, Inland Steel of East Chicago, Indiana, installed its first 76-inch-wide rolling mill capable of producing a single sheet wide enough to fabricate a one-piece steel roof.

Having the metal, however, only solved half the problem. To produce a one-piece top required a massive die and press to stamp it. General Motors Fisher Body Division redesigned their factory to accommodate the change. This included strengthening the floors to absorb the shock of forming such a large part as well as changing the transportation methods to move these large sections of raw steel from the rolling mills to the car factories. 

General Motors Corporation met the challenge in time for the 1935 model year and used the new roof on their Pontiac, Oldsmobile, and Chevrolet Master models. Their ads called it the “Turret Top” and likened its strength to that over a gun turret. They praised this innovation as tighter, stronger, and quieter. Over the next several years factories refined their manufacturing methods, and the steel top became the industry standard. Eventually the change proved to be cheaper and less labor intensive as well.

Over the next few decades “topless cars” such as convertibles and roadsters remained popular with a subset of car buyers, but many car owners preferred a solid roof.

Then in the 1960s automakers offered an option. This time they purposely cut out a segment of the roof…for sunroofs!  By then body construction was strong enough to safely accommodate such modifications. Now buyers can purchase a glass top that covers the rear seats as well! 

These modifications are so popular it is nearly impossible to get a car with a solid steel top again! 


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