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Automatic Car Question hill start watch

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    Can an automatic car roll back on a hill start?
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    (Original post by Necabo)
    Can an automatic car roll back on a hill start?
    Yes. I have proven this is possible - but it was a truck on a ridiculously steep hill.

    For average hills, no, you won't.
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    Really depends on the car. Some simply won't roll back at all if one of the forward gears are selected. Others you have to have the footbrake pressed down to activate the mechanism - with this, some will retain it until you move off, whilst others will only hold the car for a few seconds before releasing the mechanism. If you're not sure, just hold the footbrake down whilst you take the handbrake off and the mechanism will be activated.
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    (Original post by Necabo)
    Can an automatic car roll back on a hill start?
    An automatic, in gear at tickover and facing up a hill with the parking brake off will roll back if the slope is sufficiently steep to overcome the engine's effort. All automatics will creep forward in such circumstances on a level road, and it is just a matter of how steep the slope is.
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    (Original post by Necabo)
    Can an automatic car roll back on a hill start?
    It will depend on the type of automatic gearbox it has.

    Some cars are essentially a manual gearbox with an automated clutch or dual clutch, these cars will roll back on any hill unless it is also equipped with a Hill Start Assist.

    On a conventional torque converter or a CVT gearbox it would roll if the hill is sufficiently steep.
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    (Original post by Good bloke)
    An automatic, in gear at tickover and facing up a hill with the parking brake off will roll back if the slope is sufficiently steep to overcome the engine's effort. All automatics will creep forward in such circumstances on a level road, and it is just a matter of how steep the slope is.
    True in general but a lot of them have hill-start assist/anti-roll back. As I said above, some just hold the car momentarily when the footbrake is released, whereas others will actively prevent the car from rolling back at all times when it's in one of the forward gears. Mine is the former and works even on a hill that's about a 60 degree gradient near me
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    (Original post by WoodyMKC)
    True in general but a lot of them have hill-start assist/anti-roll back. As I said above, some just hold the car momentarily when the footbrake is released, whereas others will actively prevent the car from rolling back at all times when it's in one of the forward gears. Mine is the former and works even on a hill that's about a 60 degree gradient near me
    So it should: it's a mechanical means of keeping the parking brake on for a period of time that is just long enough to enable the driver to apply the accelerator and pull away. I'm not familiar with those that work via the gear box.
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    (Original post by Good bloke)
    So it should: it's a mechanical means of keeping the parking brake on for a period of time that is just long enough to enable the driver to apply the accelerator and pull away. I'm not familiar with those that work via the gear box.
    All types are basically facilitated by the gearbox, they practically just "lock" the transmission under specific circumstances until certain conditions are met. Most modern hill-start assist mechanisms will automatically lock the transmission when the engine torque isn't sufficient to hold or propel the car forward, and release it when the balance is rectified - this is mostly determined via comparing the torque to the incline via incline sensors. More recent transmissions will require the car to be at a dead stop and the footbrake depressed to activate the mechanism and will only be engaged for a few seconds once the brake is released, whereas older cars will use the mechanism whenever the torque isn't sufficient to counteract the sensed incline. Very old cars, and some newer ones as a backup mechanism, use a backward motion detector to lock the transmission when any backward motion is sensed.
 
 
 
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