Hill-Holder is a name for the mechanism invented by Studebaker[1] that holds the brake until the clutch is at the friction point, making it easier to start up hills from a stop in manual transmission automobiles. It was first introduced in 1936 as an option for the Studebaker President. Another name for the mechanism is a hill hold control (HHC).
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As a trade name, it was only available on older Subarus, and is currently available on the Subaru Forester[2] and the Subaru Impreza. The 2009 Dodge Challenger SRT8[3] also comes equipped with hill-holder. Hill-holder works by holding the brake in position while the driver sets-up and activates the first gear to move the car forward from a complete stop, without fear of roll-back.
Similar systems are or were in use by Alfa Romeo, Citroën, Fiat (including the new Fiat 500), BMW, Skoda Superb 2009, Lancia, Mercedes-Benz, Volkswagen, Lamborghini Aventador, Saab, smart ("Hill Start Assist"), Subaru, Cadillac ("NoRol") and Stutz ("Noback").
The mechanism was available in American car parts stores so that car owners could add to their vehicle to improve it from the late 1930s through the 1950s. But it required that the car have hydraulic brakes, so it could not be added to Ford Motor Company products before 1939. In 1949 it became available on factory-built Fords.. GM would not follow suit until the 2012 Chevrolet Sonic.
In layman’s terms, the hill-holder function works by using two sensors, in concert with the brake system on the vehicle. The first sensor measures the forward-facing incline (nose higher than tail) of the vehicle, while the second is a disengaging mechanism. Whether such sensors actually existed in 1939 is the subject of endless debate.
When the driver stops the vehicle on an incline where the nose of the car is sufficiently higher than the rear of the car, the system is engaged when the driver's foot is depressing the brake pedal, and then the clutch pedal is fully depressed. Once set, the driver must keep the clutch pedal fully depressed but may remove the foot from the brake pedal. To disengage the system and move the car forward, the driver selects first gear, gently depresses the fuel pedal, and slowly releases the clutch pedal which at a point in its travel releases the braking system, allowing the car to proceed.
Hill-holder works best for those who are inexperienced with manual shift techniques, or in situations with heavy traffic in steep hilly conditions (as in San Francisco, or Duluth for example).
However the same technique can be accomplished by a driver through the use of the manual parking brake lever, coordinated with the braking, clutching, shifting and acceleration.
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