Upon the establishment of the American Miniature Racing Car Association (AMRCA) in 1940, the organization published its first set of rules and regulations for governing tether car racing across the United States. That first set of rules provided for two different competition classes: Class A for cars with engine displacements of 0.36 cubic inches or less, and Class B for cars with engine displacements greater than 0.36 cubic inches up to a maximum of 0.625 cubic inches. The smaller Class A cars were typically referred to as "mite cars".
Model engines which powered tether cars before World War II used spark ignition. In addition to the spark plug and ignition timer, the engines also needed an ignition coil, condenser and battery pack. As a result, pre-World War II race cars needed to be relatively large to house all of the components of the spark ignition system. And, these relatively large and heavy cars required a relatively powerful large displacement spark ignition engine to perform adequately. A few less powerful smaller displacement spark ignition engines were available, however the cars powered by those smaller displacement engines were still relatively large and heavy because the engine's spark ignition system still required an ignition coil, condenser and battery pack.
While Class A cars built before World War II had smaller displacement spark ignition engines, the cars themselves were not much smaller than their Class B counterparts. In addition, Class A cars raced on the same size track, using the same heavy cable, as Class B cars. As a result, Class A cars appeared to be much slower and not nearly as popular as Class B tether cars before World War II.
Following World War II, however, glow plugs replaced spark plug ignition systems and the ignition coil, condenser and battery pack were no longer needed. As a result, smaller displacement glow plug equipped engines became widely available and mite cars could be made much smaller and faster.
While mite car (i.e. Class A) racing had its beginnings in the late 1930s, it did not reach its peak until the decade following World War II when Roy Cox introduced a small inexpensive toy race car, the Thimble Drome Champion, and hobbyists started powering those cars with small displacement model engines equipped with glow plugs.
As speeds increased, purpose-built mite cars were designed and built specifically for competitive racing. While most mite cars raced on flat circular cable tracks, a small number were built for racing on high-banked oval-shaped rail tracks. And, in England, small diesel-powered cars raced on road course style rail tracks.
As the popularity of mite car racing took off, hundreds of smaller tether car tracks designed specifically for mite car racing sprang up around the country. Leading that effort was Roy Cox, who developed a set of detailed plans for building a mite car track.