From bias-ply to radial-and back again
Things in the world of trail tires have changed drastically since the traction tire debuted in 1908, and especially so once recreational four-wheeling began gaining popularity in the '40s and '50s. As with so many other things, the past decade has really been a time of innovation and refinement. In the early days of four-wheeling, 9.00-15 recaps on two welded-together rims was the hot ticket for flotation. No wheel manufacturers made wide rims yet, and the military NDT treads were obviously not the ideal tire for staying on top of sand or loose dirt. It was largely the farmer's and hunter's need to get around on soft ground that drove the pioneers to invent out of necessity. Mud runners had the Firestone Super All Traction, usually in the 7.50-16 size, which fit just fine on a stock 16x4.5 Jeep CJ rim. You just couldn't steer much.
As late as 1965, Con-Ferr advertised "Wide wheels & tires" in Four Wheeler, although they were 15x7 or 14x7 wheels with 9.50-15 or 9.50-14 tires. Wide?!? Well, for the time, yes, and they were "new first line tires"-with whitewalls. You got five for $277. Spending just a few dollars more could buy you comparatively huge 11.00-15 Armstrong flotation tires (looking much like airplane treads and not necessarily DOT-approved) and rims over 9 inches wide. Of course, there was a $7.50 core charge on the wheels. Four Wheeler's Willie Worthy had his own jig for widening wheels (after cutting them apart on a lathe) by welding in a rolled steel band. You pretty much had to make your own "bolt-ons" back then, and grooving tires was more of a need than a want in those days.
Also in 1965, Armstrong introduced bias-belted tires with fiberglass belts, and BFGoodrich produced the first radial in North America (invented 16 years earlier by Michelin), but those were still all-highway tires.
PhotosView Photo Gallery
With a definite demand to fill, from little known individuals like Dwaine "Birddog" Franklin in his small Yuma, Arizona tire store to eventual celebrities such as Dick Cepek, people were working on creating more capable trail tires. They convinced Armstrong to make one of its farm tires in a highway-rated version, and the 11.00-15LT Tru-Trac was born. Dick Cepek even managed to have Denman modify industrial forklift tires for 15-inch rims, resulting in the Quiet Giant. According to Willie Worthy, Bobby Dunlap similarly created the Ground Hawg. By this time, there were also aluminum rims available, although not yet particularly light or strong, so the far less expensive (and painfully heavy) "white spoke" steel wheels were still the most popular.
In 1976, BFG introduced the All-Terrain T/A (followed by the Mud-Terrain T/A in 1980), which started popularizing the radial for the four-wheeling market, but it took until 1985 before radials dominated the original-equipment LT tire market. Another two years went by, and then the replacement market was also mostly radials. Meanwhile, Interco was busily expanding its line of Super Swamper bias-ply tires for enthusiasts.
Starting with the first-ever L78 tire in early 1970-a Swamper, which developed into the immortal TSL Super Swamper in the mid-'70s-Interco was working on mud tires while most everybody else was focused on flotation. Seems that Interco was also among the first to try making a mud tire that was usable on the street, noise-wise.