The Untold Story of Porsche's Formula 1 Disc Brakes on a 1962 Street Car
In the early 1960s, Porsche found itself at a crossroads. Disc brakes, while not exactly new in motorsport, were still novel on the streets. Jaguar and Dunlop had pioneered the technology a decade earlier at the 24 Hours of Le Mans, and Porsche was still sticking to its tried-and-true, but decidedly outdated, drum brakes. Even some of Porsche's race cars couldn't escape the clutches of drum brakes. But everything changed as the company set its sights on a successful Formula 1 season in 1962.
Engineering Brilliance: The Annular Brake System
Rather than paying Dunlop to license their advanced disc brake technology, Porsche chose the road less traveled, opting to create its own lighter and more efficient system. The traditional drum brakes were an integral part of Porsche's wheel hubs, utilizing a distinctive 'wide five' bolt pattern for mounting the wheels. Instead of re-engineering the wheel hub entirely, Porsche innovatively used the drum brake's outer face as a mounting point for the new disc brake. This clever engineering meant pushing the caliper inward, where it would clamp down on the disc's inner edge.
At first glance, Dunlop's disc brakes were more effective at high-speed deceleration but came with a significant weight penalty of 15 pounds per corner. Porsche aimed to eliminate this drawback by introducing its “Annular” brake system, which only added 11 ounces per corner. This new system provided equal stopping power without the extra weight, highlighting Porsche's engineering prowess.
The Race Track to the Road
As detailed in Karl Ludvigsen's seminal book, Excellence Was Expected, the Type 695 disc brake system was a perfect blend of innovation and practicality. Porsche’s design leveraged the existing lightweight wheel hubs inherited from Volkswagen, using five spokes curving inward to lugs on the disc's periphery. The disc brake's unique outer-edge attachment increased its diameter to 11.8 inches, improving both leverage and sweep area without adding unnecessary weight. Remarkably, the aluminum-made caliper housing two pistons on each side of the disc allowed easy pad replacement and an advanced parking brake system, solving one of the most complex challenges of four-wheel disc brakes.
In MotorSport magazine, racing legend Dan Gurney shared his mixed feelings about the annular brake setup, even though he clinched a victory in the Porsche 804. He pointed out a significant issue with pad knock-off on bumpy tracks, which forced engineers to devise solutions to keep the pads near the rotors. However, this often meant the brakes were engaged almost constantly.
The First Street Car: Porsche Carrera 2
In 1961, Porsche introduced the 356B/2000GS, informally known as the Carrera 2. This road car was almost an exact replica of Porsche’s Formula One braking system. The 2200-pound machine boasted a Fuhrmann four-cam engine with 130 horsepower, making it the first Porsche road car capable of a sub-10-second 0-60 time. With this increased power, better brakes were an absolute necessity.
Media criticism soon followed. As automotive publications like Road & Track and Auto Motor Und Sport reviewed the Carrera 2, they found fault with the existing drum brakes, which didn't perform well under the car's enhanced capabilities. Uli Wieselmann of Auto Motor Und Sport even lambasted Porsche for not making the switch to disc brakes sooner.
In stark contrast, Sports Car Graphic's Bernard Cahier had the chance to test a different prototype 356 Carrera 2, fitted with the annular disc brake setup. He was impressed by the brakes' performance, noting they required significant pedal pressure when cold but excelled after warming up, instilling driver confidence.
The Legacy and Return
By 1964, Porsche had adopted disc brakes across all 356 models with the introduction of the C model, utilizing a more conventional hub and rotor setup and introducing Porsche’s now-iconic 5x130 bolt pattern. While the annular brake system was short-lived, lasting only three years, its engineering was innovative and ahead of its time.
Perhaps, as automotive technology evolves and wheel sizes grow ever larger, it's time for Porsche to revisit and revamp the annular brake rotor and integrated brake hub design. Bring back the wide-five bolt pattern, Porsche—we dare you!