PHEV... Auto hand brake engage discovery - game changer

[Nick72]

2 hours ago, ernieb said:

I’ve been also playing with the auto wind mirror dip and I can not get it to work. I wonder if that is another dealer only function that is not documented in the manual? It would be so good to have I have a situation when we visit Derbyshire and park that there is a low level wall on the LH side and I have to drive in and reverse out, on way system, I need to accurately get the reverse turning point as there is another wall I need to miss as I drive out. The dipping mirrors would be so useful.

Definitely agree. We need it. I'll try on the US forums.

[ernieb]

8 hours ago, Nick72 said:

Cheers Pete. I think I correlated it with me pressing the brake hard like on my Merc. Mine does leap a little when I set off but maybe I'm giving it too much gas! I'll try a more gentle foot.

Seems like I got an odd default set up. No auto EPB set up and no close it all up on long press of the fob. Former fixed but looks like a dealer visit for the latter. But nowt summer is ovfer int North I don't think I'll be openin twindows till May. So I may leave it till then or just try that Carista thingy out and DIY.

 

You are a hardy sort to be opening the windows in MAY! 

[Nick72]

So far the American and Canadian cousins are saying they don't have dipping mirrors. They dont even have folding mirrors either.

[PeteB]

19 hours ago, PeteB said:

Setting off from Brake Hold on mine is really smooth... I'm always in ECO Mode, but wouldn't have thought that makes a difference.  I'll experiment tomorrow.

I've just tried moving off from Brake Hold in both NORMAL and SPORT Modes, and on my car it's just as smooth a release in all three modes.

[Nick72]

2 hours ago, PeteB said:

I've just tried moving off from Brake Hold in both NORMAL and SPORT Modes, and on my car it's just as smooth a release in all three modes.

Thanks Pete. Interesting. I just tried it a little more carefully than my previous unscientific attempts.  There's some initial resistance before a slight leap unless I very very gently and very slowly press the accelerator. 

Now if i do this on my sloping drive the leap up or downwards (doesn't matter if driving up or down) is significant no matter how softly and slowly I press the accelerator. I'm guess that the brake hold lasts longer and is stronger because of the slope?

Now wondering if I was on a sloping road when I noticed it previously and didn't make the connection. 

All manageable. 

[ernieb]

@Nick72, interesting I don’t get anything but a smooth drive, no hesitation or grab effects at all. This applies wherever I’m on the flat, up or down hill. I’ve been really impressed at how well the car handles the transition from stop to start.  Maybe just the normal variation in components and setup?

[PeteB]

1 minute ago, ernieb said:

...Maybe just the normal variation in components and setup?

Indeed. Perhaps worth asking your dealer to see if it can be adjusted next time you visit.

[Nick72]

Thanks both. I think I'll get them to look at that. Perhaps it's all still a bit sticky and lacking being worn in. Long drives coming up so I'll see how it goes. If it doesn't change for the better ill take it in.

[Thermal]

Two things happen simultaniously when you touch the accelerator to release HOLD mode.

The electronic parking brake starts to "unwind", and at the same time the normal crawling takes effect. The parking brake mechanism is a worm wheel that engages/disengages in a second or two. No need to really press the accelerator on flat or slight inclines.

[ernieb]

@Thermal, totally agree I was out playing with mine today just to see if I could make it jump and the only way I found was to be heavy with the right foot otherwise a light touch and the massive torque available will hold in almost any situation. 

[Nick72]

3 hours ago, Thermal said:

Two things happen simultaniously when you touch the accelerator to release HOLD mode.

The electronic parking brake starts to "unwind", and at the same time the normal crawling takes effect. The parking brake mechanism is a worm wheel that engages/disengages in a second or two. No need to really press the accelerator on flat or slight inclines.

That could well be what I'm doing wrong! Thanks

[Nick72]

19 minutes ago, ernieb said:

@Thermal, totally agree I was out playing with mine today just to see if I could make it jump and the only way I found was to be heavy with the right foot otherwise a light touch and the massive torque available will hold in almost any situation. 

I think Thermal nailed it. I'm in manual gearbox old cars mode!

[PeteB]

4 hours ago, Thermal said:

Two things happen simultaniously when you touch the accelerator to release HOLD mode.

The electronic parking brake starts to "unwind"

I'm sorry to disagree but I'm afraid 'Hold'  uses hydraulic pressure, not the EPB (as does holding by Cruise Control).

I was pretty certain about this, but to be sure I found somewhere quiet, turned off the A/C and opened the window.  Came to a stop, the Amber HOLD lit up, no whirring sound.  Touched the accelerator, gentle sqeak, nothing else.  Stopped again with Brake Hold on, pulled the Parking Brake switch manually and sure enough heard the motor noise.  Pressed the P switch down, heard the noise again.  The red P in a red circle lit up as expected while the Parking Brake was on.

[ernieb]

@PeteB, agree about the gentle squeak, exactly the sound I get, perceptible almost like a sticking brake, easy to miss.

[Thermal]

59 minutes ago, PeteB said:

I'm sorry to disagree but I'm afraid 'Hold'  uses hydraulic pressure...

Aha! I never noticed that subtile difference. Maybe because everything is flat here anyway and I hardly ever used Hold...

Thanks for pointing that out, I'll try to replicate this tomorrow.

BTW, the manual also states that by pulling up on the Hold button, it can be used as an emercency brake. I wonder if that is hydraulic, or the "wirring motor" EPB function. I presume the latter.  (chapter 4.2, driving procedures)

[PeteB]

1 minute ago, Thermal said:

...the manual also states that by pulling up on the Hold button, it can be used as an emercency brake...

No problem. 

That's one thing I haven't plucked up the courage to try out (yet).  Just stored it away 'just in case' but hope never to need!

[philip42h]

28 minutes ago, Thermal said:

BTW, the manual also states that by pulling up on the Hold button, it can be used as an emergency brake.

No, I don't think you mean the Brake Hold button, I believe the manual refers to the Parking Brake switch. I really hope that I never have to try that ...

In an old fashioned car, the handbrake was a cable  attached, mechanical system, that applied the rear brakes (typically). This served two functions: it held the car while at rest, and could be used in an emergency if the hydraulics failed.

In a modern RAV, they made things more complicated. As far as I can tell (and consistent with what is said above) the Parking Brake simply locks the gearbox; while the Brake Hold switched runs a pump to pressurise the hydraulic system to apply the brakes. So, Brake Hold would be 'useless' in the event of a hydraulic failure.

While running a worm gear to drive a dog into the cogs of the gearbox while the car is moving might well stop the car, it's not something I want to try with my gearbox. It looks like the days of the handbrake turn are numbered ... 😉

[PeteB]

1 minute ago, philip42h said:

No, I don't think you mean the Brake Hold button ...   good spot - I missed that

In an old fashioned car, the handbrake was a cable  attached, mechanical system, that applied the rear brakes (typically). This served two functions: it held the car while at rest, and could be used in an emergency if the hydraulics failed.

In a modern RAV, they made things more complicated. As far as I can tell (and consistent with what is said above) the Parking Brake simply locks the gearbox; while the Brake Hold switched runs a pump to pressurise the hydraulic system to apply the brakes. So, Brake Hold would be 'useless' in the event of a hydraulic failure.

While running a worm gear to drive a dog into the cogs of the gearbox while the car is moving might well stop the car, it's not something I want to try with my gearbox. It looks like the days of the handbrake turn are numbered ... 😉

I think the "P" position on the gear selector engages the parking pawl and the Auto or Manual Parking Brake switch uses a motor to apply (hopefully at least 2 - probably rear) wheel brakes mechanically.  I would further hope that pulling and holding it while moving would use software logic to apply these brakes with enough force to slow the car but not enough to cause it to lose control.  But I'm too chicken to try it out even at low speed in a car park. 🐔

I'll be booking my tyre swap for the winter next month and I've made a note to ask for another look under the car while it's in the air and I'll see if any of the technicians can fill in some blanks about this.

[philip42h]

1 hour ago, PeteB said:

I think the "P" position on the gear selector engages the parking pawl and the Auto or Manual Parking Brake switch uses a motor to apply (hopefully at least 2 - probably rear) wheel brakes mechanically.  I would further hope that pulling and holding it while moving would use software logic to apply these brakes with enough force to slow the car but not enough to cause it to lose control.  But I'm too chicken to try it out even at low speed in a car park. 🐔

I'll be booking my tyre swap for the winter next month and I've made a note to ask for another look under the car while it's in the air and I'll see if any of the technicians can fill in some blanks about this.

Yup, that's better - I was combining the function of Park and the Parking brake  ... 

It is as you describe ... and 'worse' I found a YouTube description of the component parts (from the US)  😞

Maybe the handbrake turn rides again! 😁

[Thermal]

3 hours ago, PeteB said:

 I'll see if any of the technicians can fill in some blanks about this.

Yes, let us know what you see and what the technician says.

After reading that section of the manual (again... 😒) I'm almost convinced that pulling and holding that HOLD button activates the mechanical parking brakes on the rear wheels, as a measure of last resort. That will probably mean a write off of the expensive EPB, but if you find yourself speeding down a hill at 100 miles per hour with a hydraulic failure, you should be in a different class of "financial awareness" 😲

[Nick72]

5 hours ago, philip42h said:

No, I don't think you mean the Brake Hold button, I believe the manual refers to the Parking Brake switch. I really hope that I never have to try that ...

In an old fashioned car, the handbrake was a cable  attached, mechanical system, that applied the rear brakes (typically). This served two functions: it held the car while at rest, and could be used in an emergency if the hydraulics failed.

In a modern RAV, they made things more complicated. As far as I can tell (and consistent with what is said above) the Parking Brake simply locks the gearbox; while the Brake Hold switched runs a pump to pressurise the hydraulic system to apply the brakes. So, Brake Hold would be 'useless' in the event of a hydraulic failure.

While running a worm gear to drive a dog into the cogs of the gearbox while the car is moving might well stop the car, it's not something I want to try with my gearbox. It looks like the days of the handbrake turn are numbered ... 😉

Did that by mistake on the last PHEV. Engine orvdrive mode button tight next to parking brake and similar style buttons. The parking brake really did work at speed. Scared the life out of me.

Think the human factors engineer must have been on a sabbatical! 

[Cyker]

I'm sure they tried this in a topgear episode or something - IIRC they tried it in a Golf. Forcing the EPB to engage will make the electric motor wind in the caliper like it does normally, and it will slow the car to an eventual stop, but it does it gradually/progressively (Not sharply like yanking on the handbrake) and doesn't provide enough force to lock the wheels at any speed so handbrake turns are definitely off the table!

It shouldn't damage the EPB tho'. (Not that I'm condoning anyone try this.. I'm deffo not going to!!)

[Lawnmowerman]

In 'Ministry' terms the handbrake is considered an emergency brake. As an MOT item, the emergency brake had to achieve an efficiency of 25%. Jaguar (many moons ago) were THE early adopter of Dunlop disc brakes but, to their dismay, it could not achieve the required 25%. So, the Ministry decided that as the car was fitted with dual circuit brakes they could reduce the threshold to 16% - which it could achieve. Because of the (relatively) low effort being applied by a mechanical handbrake as opposed to the effort from hydraulic pressure, disc brakes generated less stopping power than brake shoes (which had a self-servo action lacking in disc brakes). 

So, if the car had single circuit brakes - 25%, and if it had dual circuit brakes - 16%. 

How it is applied in the RAV (and other manufacturers with EPB is beyond my ken now - feel more like a historian 😂).

[Nick72]

21 hours ago, Cyker said:

I'm sure they tried this in a topgear episode or something - IIRC they tried it in a Golf. Forcing the EPB to engage will make the electric motor wind in the caliper like it does normally, and it will slow the car to an eventual stop, but it does it gradually/progressively (Not sharply like yanking on the handbrake) and doesn't provide enough force to lock the wheels at any speed so handbrake turns are definitely off the table!

It shouldn't damage the EPB tho'. (Not that I'm condoning anyone try this.. I'm deffo not going to!!)

There was nothing slow and progressive about it on my last PHEV SUV. When I pulled it by accident thinking I was changing engine modes. It was equivalent to pulling the handbrake. It was a slam on.

Must depend on implementation. 

[Cyker]

Yeah I didn't convey that right at all - I didn't mean slow, I meant progressive like how you're taught to do an emergency brake properly (i.e. you don't just slam on the brakes, but apply rapid and progressive pressure so you can stop the car quickly and in the shortest possible distance but without risking locking the front wheels up, like you would if you'd just slammed on the brakes) - It will brake quite forcefully, but it won't and can't apply the brakes in the instantaneous way you'd do it with a handbrake if you were trying to do a handbrake turn.