New Montreal Loaner

[llavalle]

Nope, my classic P85 has not changed this behavior at all. It hill-holds on steep inclines. It does not apply the brakes whenever you stop, and there's no symbol on the dashboard for this.

Technically, the AP cars do not apply the brakes whenever you stop. You have to depress the pedal a bit more for Vehicle Hold to engage...

The thing is : that bit more is very little and you end up with it engaging most of the time.

 

[Peter_M]

Nope, my classic P85 has not changed this behavior at all. It hill-holds on steep inclines. It does not apply the brakes whenever you stop, and there's no symbol on the dashboard for this.

Doug, classic cars like yours and mine apparently don't have the hardware to implement the "vehicle hold" - we're stuck with just the "hill start assist". I'm not sure what the limitation is - maybe since they are using ABS / stability control hardware to hold the brakes, it can only hold for a second or two, whereas AP cars with their electric assist can hold the brakes indefinitely.

 

[Doug_G]

Makes sense. There are a lot of little refinements in there.

 

[mknox]

Doug, classic cars like yours and mine apparently don't have the hardware to implement the "vehicle hold" - we're stuck with just the "hill start assist". I'm not sure what the limitation is - maybe since they are using ABS / stability control hardware to hold the brakes, it can only hold for a second or two, whereas AP cars with their electric assist can hold the brakes indefinitely.

Yes, but why can't classic cars have the hill start assist engage every time rather than just when the hill is beyond some threshold? The second or two of hold is plenty.

 

[SmartElectric]

Yes, but why can't classic cars have the hill start assist engage every time rather than just when the hill is beyond some threshold? The second or two of hold is plenty.

Likely due to the way the braking system in the AP cars is an electro-mechanical system, whereas the hill hold in the classic cars *(like ours) is based on the emergency brake system.

I would presume there is almost certainly a very good reason for not over working the emergency braking system in classic cars.

 

[mknox]

Likely due to the way the braking system in the AP cars is an electro-mechanical system, whereas the hill hold in the classic cars *(like ours) is based on the emergency brake system.

I would presume there is almost certainly a very good reason for not over working the emergency braking system in classic cars.

It could be, but I'm not convinced that's it. If I lived in San Francisco the system would be working all the time. I have found that the threshold for when it comes on is just above the point of most inclines I stop on. Enough for me to get roll-back when I take my foot off the brake, but not enough for the system to engage. If I let it roll back, then "jerk" the car to a stop, it will hold. Presumably, I've given the accelerometer enough of a nudge to get it to register. It does work well enough on steep inclines.

I was one of those who felt it was an unnecessary addition to the car in the first place. Hill hold is good for manual transmission cars where you have three pedals to work with two feet. But in the Model S, it is easy enough to hold the brake with one foot and let up on it as you press the accelerator. But the problem is with the feature in place, I never know if it is going to work or not.

 

[PoweredByRain]

It could be, but I'm not convinced that's it. If I lived in San Francisco the system would be working all the time. I have found that the threshold for when it comes on is just above the point of most inclines I stop on. Enough for me to get roll-back when I take my foot off the brake, but not enough for the system to engage. If I let it roll back, then "jerk" the car to a stop, it will hold. Presumably, I've given the accelerometer enough of a nudge to get it to register. It does work well enough on steep inclines.

I was one of those who felt it was an unnecessary addition to the car in the first place. Hill hold is good for manual transmission cars where you have three pedals to work with two feet. But in the Model S, it is easy enough to hold the brake with one foot and let up on it as you press the accelerator. But the problem is with the feature in place, I never know if it is going to work or not.

Live in a more hilly area and you'll appreciate it.

It almost always engages for me, and if it doesn't engage then it's not enough of a hill to worry about.

 

[Peter_M]

Likely due to the way the braking system in the AP cars is an electro-mechanical system, whereas the hill hold in the classic cars *(like ours) is based on the emergency brake system.

I would presume there is almost certainly a very good reason for not over working the emergency braking system in classic cars.

If by "emergency brake" you mean the parking brake, then no - the hill hold feature doesn't use the parking brake. You can tell by opening your window when you engage the hill hold. You won't hear the characteristic "zip" sound of the parking brake engaging or disengaging.

 

[Doug_G]

As I understand it, the hill hold on classic cars uses the ABS system. Maybe that's what mknox meant by "emergency". They can probably only hold the brakes for a couple of seconds.

The autopilot cars must have an electric hydraulic piston for actuating the brakes. They would need that in order to stop the car. That would be very easy to use to hold the brakes on while the vehicle is stopped.

 

[mrElbe]

Just drove to North Carolina yesterday and today. On my Autopilot car I observed that the "hill hold" will work in every instance when I press hard on the brake when standing still. During this hold, the brake light is on. Very convenient at long stop lights.