Disc brakes have been hardly a brand new know-how in 1962, as Jaguar and Dunlop had examined the idea within the crucible of motorsport as early as a decade prior on the 24 Hours of Le Mans. Up so far within the firm’s historical past, Porsche had been utilizing tried and true (and low cost) drum brakes, even on all however a number of of its racing vehicles, however the firm needed to construct a successful Formulation 1 automobile for the 1962 season and wanted higher brakes. As a substitute of paying Dunlop to license the know-how, Porsche set about engineering its personal system, and making it lighter.
Porsche’s present wheel hubs all used the drum brake as an integral a part of the nook, mounting the wheel on its face in a “extensive 5” bolt sample. Due to the corporate’s engineering experience with this trend of mounting, it determined to make use of the face of the drum brake because the outer mounting level for a brake disc, and pushed the caliper to the within of the hub making use of clamping pressure throughout the internal edge. The Dunlop system proved way more succesful at braking from excessive speeds and repeatedly than drum brakes, nevertheless it got here with a major 15-pound weight penalty per nook. The brand new Porsche-developed “Annular” brake system was simply 11 ounces heavier than its drum system, and will cease simply in addition to the British-designed system.
From Karl Ludvigsen’s tome in regards to the historical past of Porsche “Excellence Was Anticipated” recounting the development of the corporate’s light-weight annular brake system:
“The kind 695 disc brake was tailor-made to achieve particular benefits from the attribute Porsche wheel design, which was inherited from Volkswagen. The British disc ideas pressured the usage of standard wheels with a lot heavier hubs as a substitute of the sunshine Zuffenhausen mixture of a burdened brake drum married to an open-center wheel. For their very own brake the Porsche designers saved the aluminum wheel service and gave it 5 spokes curving inward to lugs on the periphery of the brake disc. Thus the disc was hooked up to the rotating mass via its periphery, like most plane disc brakes, as a substitute of via its internal edge, the design favored by British corporations.
This distinctive mounting of the Porsche disc allowed it to have the most important doable diameter (11.8 inches). This elevated each the leverage and the swept space of the disc with out making it overly heavy, for it consisted of solely a hole ring of iron. It was gripped from the within by the caliper, which was made, uncommonly for these days, of aluminum.
The caliper housed two pistons behind rectangular lining pads on all sides of the disc. Its pads may very well be eliminated and inserted via areas between the disc-supporting arms. And superior characteristic of the Sort 695 brake was its parking brake: a easy pare of increasing footwear at every hub, which labored on the internal edge of every rear disc, successfully fixing probably the most troublesome issues posed by a four-wheel disc system.
MotorSport journal spoke to Dan Gurney about his solely race win within the 804 again in 2003, and he was not notably pleased with the annular brake setup on his Formulation One automobile.
“There was a considerable amount of pad knock-off on bumpy surfaces in order that they used varied means to maintain the pads near the rotors,” stated Gurney. “That primarily meant you had the brakes on more often than not.”
When Porsche launched the 356B/2000GS, informally often called the Carrera 2, in 1961, it was geared up with the practically precisely the identical braking system because the F1 automobile. The 2200 pound racing model of Porsche’s profitable street automobile was geared up with a technologically superior Fuhrmann four-cam engine making 130 horsepower. This was the primary Porsche street automobile able to a sub-10-second 0-60 time, and it completely wanted higher brakes to maintain that further energy in verify.. Extra from “Excellence Was Anticipated”:
“The vehicles tried by Highway & Observe and Auto Motor Und Sport have been geared up with regular Porsche drum brakes, which didn’t please the German publication in any respect. The higher acceleration and higher weight of the Carrera 2 imposed, it stated, ‘the restrict of standard brakes. On our take a look at roads they pale and pedal journey elevated considerably, in order that the answer of the disc brake now intrudes itself. Sadly the corresponding determination hasn’t but been made at Porsche—incomprehensibly, one may say.’”
Auto Motor Und Sport editor Uli Wieselmann knew he would strike a nerve with Porsche brass. The corporate had been testing disc brakes (each Dunlops and internally-designed items) on its racing vehicles since 1958, however hadn’t fairly dedicated to putting in them on street vehicles. It appears automotive media’s derision for the drums and reward for the discs may need pushed Porsche over the sting in favor of the novel braking idea.
A distinct prototype 356 Carrera 2, fitted with the annular disc setup, was examined by Sports activities Automobile Graphic’s Bernard Cahier on the similar time, and he praised the system, saying:
“The extra I drove this automobile the extra confidence I felt in these brakes. Since there was no booster they required a great quantity of stress from the brake pedal. Certainly, when the brakes have been chilly they wanted way more stress and didn’t appear to cease as shortly as they need to have, whereas after a number of consecutive stops they turned actually good, with much less stress required on the pedal.
By 1964 all Porsche 356 fashions have been moved to a disc brake with the introduction of the C mannequin, although with a way more conventional hub and rotor setup, and the introduction of Porsche’s now-signature 5×130 bolt sample. The system was actually solely in place for 3 years, however the engineering behind it was sound. Maybe it’s time to as soon as once more embrace the annular brake rotor and built-in brake hub, particularly as wheel sizes balloon. Convey again the wide-five bolt sample Porsche, you cowards!
