Originally posted by m9a3r5i7o2n
Art stated; I'd bet that Firestone did little more than create new vulcanizing molds to make those into racing tires back then.
From what I have been able to glean from statements of other people I’d state that you are right, Firestone didn’t seem to have a lot of interest in pushing the envelope further into the future until Goodyear got back into the business of making racing tires sometime ago.
It is probably almost an accident that they made the Balloon Tire about 1925. From pictures I have seen in the book, “The Miller Dynasty” and Ludvigsen‘s book, “Indy Cars 1911-1939, the tread on those looked about 3 inches wide. As near as I can tell the Balloon tire came out in 1925. The picture on page 70 definitely shows the White letters on each tire as, “Firestone Balloon“. The Firestone picture on page 49,1925, seems to have Balloon on it but not in White lettering. This was the time that the tire pressures dropped from about 100 p.s.i.g. to around 30 p.s.i.g.. So this seems to confirm that the Balloon tire came out some where around the 1925 period. After that there were none that I can find that weren’t Firestone of one type or another. There are no Dunlop pictures after 1926 in evidence in either book.
The 1935 cars had 6.000-18 written on them, page 113 of Ludvigsens book.
Also on page 111 there is a picture and a statement of “an example of the classic full-floating “safety” hub using a 310 series ball bearing. The axle may break, or be replaced ,without affecting the wheel hub itself. This pattern was used on nearly all American racing cars until the open tube rear end came into general use after WW2. The picture shows a 52mm RW Hub. It surely does not look very strong. No wonder the open tube replaced it.
Tomorrow, Monday, I will try some of the places mentioned especially Coker and see what happens.
Yours, M.L. Anderson 
Marion,
The period 1925 to 1941 wasn't known for significant advancements in tire technology by anyone, frankly--not Firestone, not Goodyear, not BF Goodrich, not anybody. Tire sizes got smaller and wider through about 1935-36, finally standardizing at 16" diameter by then, which remained pretty constant until 1948-49. The rubber used was natural latex rubber, synthetic rubber would wait until the necessity of the Second World War, and then expand into mass-produced civilian tires after the war--although civilian tires were made during the war--ever see the characters S-1, S-2, and S-3 on old tire sidewalls? Those denoted synthetic rubber on wartime tires. Nor had synthetic fibers made it to tire casings, until the need for massive numbers of high pressure aircraft tires during the war--enter nylon tire cording. Until then, every US tiremaker was using cotton cord for making tire casings.
Tire tread width (or the lack thereof) did not a balloon tire make or break--but rim and casing width did. The balloon tire concept stems from the near-circular cross section of the inflated tire casing, not tread witdths. Race cars of the teens through the early 20's ran on tires with much more an "oval" cross-section, more tall than wide, hence the term "straight-sided tire", with a "clincher" rim, which gripped the tire casing by virtue of the rim having been rolled into almost a C-clamp configuration, the tires themselves running upwards of 90-95psi pressure. Also, those early tires were much, much narrower in cross section, and were measured, not by rim diameter, but by tread diameter and rim width. Racing tires, at least in Speedway racing, continued having a narrower tread in comparison to the width of their casings, all the way to the eve of US entry into WW-II, pictures clearly show that, along with the tires on cars at Indianapolis Motor Speedway's Museum. (One of the perhaps little-known things about the Musuem is that Firestone built up a pretty fair supply of older racing tire sizes for the Speedway Museum in the late 50's/early 60's, before they began disposing of old tire molds--such was the relationship enjoyed by Tony Hulman Jr. (one of the pioneers of the antique car hobby, a founding member of AACA in 1936, BTW, and Firestone Tire & Rubber in those years). I had the opportunity, once, about 1977 or 1978, to have a tour of the "supply building" used by the two men responsible for restoration and maintenance of the Museum's growing collection--rack after rack of old-style Firestone racing tires, nicely wrapped from the factory, in all manner of old sizes.
Balloon passenger car tires of the 1930's, such as would have been on your favorite car, the Oakland, ran a lower pressure than the old high-pressure "clincher" tires (those clinchers require about 79-75psi) or in the range of 45-50psi. It wasn't until the coming of the really low-pressure 15" tires of 1948-49, along with nylon and rayon casings that tire pressures on passenger cars dropped to 35psi. Tire treads on passenger cars could, of course, be built up at the edges, for a wider tread, simply because they weren't running the incessant high speeds of a race car. so heat buildup in the treads coupled with centrifugal force wasn't nearly the problem it would have been in racing. Where a passenger car tire of the 30's, built with 6, and in some cases, 8 ply casings, might be more than an inch thick at the center of the tread, race tires were, just as they are today still, far thinner, probably no more than 1/2" thick at the center of the tread. Wide tread, built up thickly at the edges on a round cross-section casing, simply would not have held up, certainly not vulcanized natural latex rubber, although race tires did get some buildup of the tread edges by the late 30's.
In 1994, at the first Miller Race Car Reunion at Wisconsin's Milwaukee Mile, one of the 1938 Burd Piston Ring Specials showed up, an all original car, down to a set of tires which had been the last tires mounted during a pit stop at Indianapolis in 1938, Firestone gum-dipped cotton cord racing tires! This car, regardless of intelligence or the lack thereof, was run that weekend, in 100-degree July weather, until the owner had to pull it off the track due to the breaker strip showing. Chris Etzel and I measured and photographed this car extensively (it was a 2-man car, memory tells me that it dated to about 1931-32, with updated bodywork) I seem to recall its tire sizes as having been 6:00-18 rear, 5:00-16 front, with the rear tread width being 5", or just about 1/2" narrower than a comparable 16" passenger car tire of the day. I believe we read on the sidewall, the legend: 8-ply, again quite consistent with larger passenger car tires of the period. Firestone Tire and Rubber, with the development of their balloon tires, had developed, and patented, a process whereby they soaked the cotton cord in clear gum rubber, before winding it into tire casings, which ostensibly reduced the wear of the plies of cotton cording rubbing against each other as the tire casing flexed in passenger car use. Whether or not it was significantly effective or not, I cannot tell, as my father, who was on the road daily in his job in the years 1937-69, constantly reminded me that until the postwar years, he could not get more than 10.000 miles out of a set of tires before the war, which seems to have been pretty much the norm with those old cotton tire casings. Dad used Firestones, as well as other makes of tires back then--he bought on price, not on brand.
Tire technology, just as with much of the rest of automotive technology, developed but slowly in those years, frankly.
Art
