Hill start assist

[Alienburt]

Got to the top of a slight incline and the car started rolling backwards - powershift box set to D. Obviously it held with the brakes but thought auto gearbox should hold it or hill start assist should kick-in. Is this normal or do I have a problem?

Thanks

[Sealiedog]

The incline needs to be above a certain angle for hill start, not sure how much, but its 5 degrees on my Fiat. Auto creep is not likely to hold you uphill, in my experience the Powershift box creeps less than a standard auto. It sounds OK to me if its a slight incline.

[Sealiedog]

I think maybe the Ford system works all the time and doesnt need an incline. I think this explains it: https://www.ford.co.uk/shop/research/technology/driving-experience/hill-start-assist

Of course you have to have applied the brake first.

[Alienburt]

Thanks for the replies. It seemed more than 5 degrees and had braked while waiting at the top of the slope. Released the brake and she started rolling back. I had an S-Max before with powershift and I'm sure that didn't happen

[Mike's living on the Edge]

I've noticed the Edge rolling backwards on slopes when the transmission is in Drive. A little disconcerting since my other autos have not done this. It only seems to happen if you brake to a stop on a hill then immediately go back to the throttle. My Edge seems to want to stop completely for a second before it realises it is on a hill. If I hold it on the brake for a second it then behaves as expected with no roll back. No big deal once you get used to it. 

I think it must be the way the ECU is programmed? There seems to be a bit of a delay somewhere 

[simonb65]

For the operation of Hill Start Assist, you must brake until completely at a stand still before Hill Start is activated, but it does take half a second or so for the system to lock the brake pressure. I guess it needs that small amount of time to evaluate the angle of the car as doing it during the braking it would not read correctly due to the deceleration. The time between wheel speed measurements at less than 1 or 2 mph takes a few 100mS too as the distance between ABS 'teeth' is not fine enough (After all, you don't want it to apply the brakes fully until you've actually stopped rolling !!). It then stays engaged for up to 2.5 seconds after brake release.

Never seen an issue in mine, although I never fully stop if I don't need to and I anticipate traffic moving off again, so I either stop fully for a few seconds or keep rolling using the auto's creep behaviour! If I do stop, I don't go until the car in front has pulled away with some margin ... don't want some 'manual' jockey stalling or rolling back into me 😉