1949–1950 Crosley Hydradisc Brakes: The First Disc Brakes On An American Car

In mid-1949, Crosley cars and trucks like this diminutive Crosley Hotshot roadster became the first American production models equipped with disc brakes, months ahead of Chrysler (and years before Studebaker, which often gets the credit for that particular innovation). Although they were dropped after only one year, the four-wheel Crosley “Hydradisc” brakes were a real advance in the field of automotive braking. Not only were they introduced before the more famous Dunlop disc brakes, their inventor’s work later resulted in several Dunlop brake patents being declared invalid! Let’s take a look at Hydradisc and clear up some common misconceptions about it.

Jeff Nelson has already ably recounted the history of Crosley Motors, so it’s not my intention to recap that here except to note that the maker of these toy-like American mini-cars tried a number of rather bold experiments, some of which didn’t pan out. Among these were the unusual but unreliable CoBra engine, with its peculiar copper-brazed steel cylinder block. Another, introduced months after the CoBra engine had been replaced by a more orthodox cast iron block four, was Hydradisc brakes.

Disc brakes are now over 120 years old: The first iteration was invented by English engineer Frederick W. Lanchester, who patented his design in Great Britain in 1903.

However, disc brakes were not very successful in early automotive applications, and they remained rare even on race cars well into the 1950s. As the above Crosley brochure indicates, the more important disc brake application in the 1940s was for aircraft landing gear, where the heat dissipation ability of discs proved invaluable in stopping increasingly heavy aircraft with increasingly high landing speeds.

With their 724 cc four-cylinder engines, the tiny Crosley cars were neither very heavy nor very fast — the new Hotshot roadster, introduced in July 1949, had a shipping weight of under 1,200 lb and a top speed of about 72 mph in stock form — but Powel Crosley nonetheless decided to make four-wheel hydraulic disc brakes standard across the entire Crosley line from May 15, 1949. For those keeping score, that was about five months before the introduction of the 1949 Chrysler Crown Imperial with its very different type of four-wheel disc brakes.

The Hydradisc brake was designed by Jesse G. Hawley, vice president of the Hawley Brake Corporation of Corning, New York. Crosley had an existing business relationship with Hawley: The cable-operated drum brakes on earlier Crosley models had used Hawley Floating Linings, an innovation Hawley had been marketing since around 1935.

Because Hawley had previously licensed his disc brake designs to Goodyear Aircraft Company for aircraft landing gear, and because Crosley proudly advertised Hydradisc as “ultra-modern hydraulic brakes of the type used on the latest military planes and modern commercial aircraft,” there’s a common misconception that the Crosley discs were repurposed aircraft brakes, which is untrue. (In any case, brakes of the size Crosley used would have only been useful for VERY light aircraft.)

In fact, Hawley had also been working on automobile disc brakes since at least 1943, and had installed a prototype set on his own 1941 Ford coupe. For a while, he had a licensing deal with Goodyear for non-aircraft applications of his brake designs — he even sold them his disc-braked ’41 Ford in 1944 for testing and engineering evaluation — but Goodyear eventually conceded defeat in their efforts to interest Detroit automakers in disc brakes after the war.

Hawley subsequently developed the Hydradisc brake specifically for “automobiles and light vehicles,” with an eye towards minimizing cost, weight, and service headaches. He attempted to patent the design in April 1949, about a month before Crosley introduced the new disc brakes in production, although he abandoned his initial application and refiled in November. The patent was issued in October 1952 as US2614662. While Crosley Hydradisc brakes were often described at the time as “Goodyear-Hawley brakes,” the patent was actually assigned to Hawley Brake Corporation, NOT to Goodyear. (The “Hydradisc” name, meanwhile, was conceived not by Hawley, but by copywriter Mary Ann Kelly of the Ralph H. Jones Co., Crosley’s ad agency.)

Except for its size, the Hydradisc brake will look familiar to modern readers: It was a single-piston caliper disc brake of the floating-piston type, with two tiny 1.25-inch friction pads acting on either side of a 7.5-inch cast iron rotor. It had several novel features: First, each piston could be actuated either hydraulically or mechanically, and all four brakes were engaged whether you pressed the brake pedal or used the handbrake. (Hawley’s patent said the mechanical engagement cam for the front brakes could be omitted so the handbrake would only work on the rear wheels, but Crosley decided not to do that.) Second, Hydradisc had one-point adjustment, allowing the pad clearance to be adjusted by turning a single screw, which had a clicker mechanism to aid adjustment (you loosened the lock nut, tightened the screw until the wheel locked, and then backed off four clicks), a chore Crosley claimed only needed to be done once a year in normal driving.

Contrary to the assertions of some historians, including the normally reliable Richard M. Langworth, the disc brakes were NOT limited to the new Hotshot roadster, and were already in production about six weeks before the Hotshot debuted. This August 1949 magazine ad emphasizes that Hydradisc brakes were “now standard equipment on all Crosley cars”:

When they were in good working order, Hydradisc brakes provided a lot of braking power for a car the size of a Crosley, and they were a big step up from the previous mechanically actuated 6-inch drums. Unfortunately, the Hydradisc brake’s Achilles heel proved to be corrosion, particularly in areas that used road salt. Although the back of each Hydradisc brake had a dust cover, you’ll notice that there was no splash shield on the caliper itself. Crosley claimed that centrifugal action would keep the disc clear of water, snow, or mud, while friction heat from the pads would wipe the rotors clean of moisture, but salt was another matter, and the resulting corrosion could cause the brakes to seize.

New York Crosley distributor Ed Herzog later insisted that most of the corrosion problems could have been avoided by better shielding the brake, which would have been a fairly straightforward upgrade. However, Powel Crosley apparently decided that revising the design would be throwing good money after bad. Crosley Motors had posted a million-dollar loss for fiscal 1949, and total Crosley sales were down almost $11 million from 1948, so the warranty costs related to the Hydradisc brakes were an unwelcome additional expense I assume he wasn’t eager to compound.

Instead of taking steps to mitigate the brake corrosion problem, Crosley simply abandoned the Hydradisc brakes after May 1950 and substituted conventional 9-inch Bendix drums. This left Hawley holding the bag, with 9,250 complete sets of Hydradisc brakes that now wouldn’t be used. Hawley responded by suing Crosley for breach of contract, a matter settled out of court in 1951. A year later, Powel Crosley sold Crosley Motors to General Tire and Rubber Company, and Crosley production ended for good.

However, for about a year, every Crosley model had four-wheel discs, even the curious Farm-O-Road utility vehicle. Based on monthly production figures, I estimate that Hydradisc brakes may have been installed on as many as 7,400 Crosley cars and trucks in 1949–1950: about 4,600 in calendar 1949 and about 2,800 in calendar 1950. That wasn’t a lot by Detroit standards, but it was a lot more than any other U.S. automaker would sell until the mid-1960s.

Some Hydradisc-equipped vehicles were retrofitted with drums, which were perfectly adequate for cars of such limited size and power. It’s not clear how many Crosley vehicles still retain their original discs; to my frustration, many sale and auction listings don’t bother to mention the brakes one way or the other. (While the bright yellow Super Hotshot pictured below reportedly does retain disc brakes, the seller didn’t see fit to include pictures of them.)

Although Jesse Hawley didn’t ultimately have much luck with passenger car disc brakes beyond his initial deal with Goodyear and whatever he got from Crosley, his and Goodyear’s efforts to commercialize his automotive disc designs in the ’40s later led a U.S. federal district court to invalidate three 1950s Dunlop disc brake patents. Dunlop had sued Kelsey-Hayes for infringing four Dunlop disc brake patents, but the court ruled that three of those patents were actually invalid because they were insufficiently different from Hawley’s earlier designs to be patentable under U.S. law. Dunlop appealed, insisting that “the Hawley automobile brake was an incomplete experiment, abandoned by Goodyear, and ultimately discarded,” but the appeals court wasn’t persuaded, and upheld the district court decision. In 1974, the Supreme Court declined to review the case, allowing the lower court ruling to stand.

Curiously, while the court found that Hawley’s 1943 brake design was “substantially identical” to the later Dunlop US2790516 patent, it appears no one on either side of the case ever brought up Crosley. The fact that a later iteration of Hawley’s disc brake design had been used on production automobiles, however briefly, seems like a decisive rebuttal of Dunlop’s contention that Hawley had abandoned and discarded his disc brake designs. Since the appeals court rejected the Dunlop argument anyway, it ultimately didn’t make much difference.

Invalid patents or no, it was still Dunlop, not Hawley or Crosley, that really put automobile disc brakes on the map in the ’50s, thanks largely to the exceptional performance of the Dunlop-Girling six-piston disc brakes on the Jaguar XK120C that won Le Mans in 1953.

Even if the Crosley discs had been more reliable (which really wouldn’t have taken much — I think Ed Herzog was right about that), I doubt they would have made much impression on Detroit. On the one hand, the Crosley was an itty-bitty car with a little engine, so it didn’t particularly NEED discs. On the other, because it was so small, a lot of the disc brake issues that later became sticking points for Detroit didn’t really apply: A Crosley didn’t need a brake servo for reasonably low pedal effort, it didn’t need ventilated discs for adequate pad life, and its four-wheel emergency brake setup was probably fine, none of which was necessarily true for bigger, heavier American cars.

It was probably the Hotshot that would have most benefited from well-sorted disc brakes — contemporary MG roadsters still had drums, and discs didn’t show up on any other affordable sports cars until the 1957 Triumph TR3. However, as it was, the Hotshot proved surprisingly competitive in the under 750 cc racing classes with or without Hydradisc brakes.

Like so many early adopters of new technology, Crosley had the right idea, but just took it out of the oven a little too soon.

Related Reading

The Rise and Fall Of The Crosley Automobile (by Jeff Nelson)