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hill desent runaway.
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robpenrose
 


Member Since: 12 Jan 2016
Location: Surrey / SW London
Posts: 2136

United Kingdom 2010 Discovery 4 3.0 TDV6 HSE Auto Stornoway GreyDiscovery 4

That "might" be what the described run away is. The car might increase speed to get traction then try to reduce speed again!

I haven't done a lot of driving in slippery stuff in the D4. I've done a lot in my old 90 defender as I lived in the Alps for 3 years.

I often found 1L too short when it's very slippery as it can be harsh when on and off the gas and cause jolting etc, which can be enough to break traction. You need to be very gentle with the controls.

Once the car starts to slide, you usually need a lot of space to sort it out, which is usually the problem!
 

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Post #17991693rd Apr 2017 6:07 am
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L319
 


Member Since: 14 Dec 2013
Location: Herefordshire
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United Kingdom 2005 Discovery 3 TDV6 HSE Auto Buckingham BlueDiscovery 3

If it starts to slide you need to open the throttle to get the vehicle & wheel speeds matched and then slowly close it again. , but you need plenty of space & its rather counter intuitive the first time you need to do it. It s best to find a space to try, rather like having a go on a skid pan, to get the hand of it. HDC is very good but if there is insufficient grip it will go!
  
Post #17991793rd Apr 2017 7:57 am
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DG
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Member Since: 12 Dec 2005
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Wales 

garrycol wrote:

The car might slide a bit but will not run away


In the right (or wrong) conditions it will. My schoolboy error was that the slope was too steep, far too wet and once sliding the corrective action of trying to move the wheels onto more solid ground just pulled the back of the motor around and bang ! I think if I hadn't hit something half way down then I would have been really hurtling to the bottom Laughing
 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021  
Post #17991813rd Apr 2017 8:06 am
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JPW
 


Member Since: 19 Mar 2007
Location: Essex
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United Kingdom 2013 Discovery 4 3.0 SDV6 XS Auto Orkney GreyDiscovery 4

I thiught I'd seen something about HDC being affected by high / low range.
the owners manual says;

During a descent, HDC will maintain a target speed of up to a maximum of 20 km/h (12 mph) in low range, and 30 km/h (19 mph) in high range.
  
Post #17992003rd Apr 2017 8:51 am
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DSL
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Ukraine 

In some conditions even the minimum speed that you can dial in is scarily fast. The manual didn't anticipate the crazy things we do with these cars. You have a choice, feet off the pedals and go too fast or control the decent using HDC and the brakes. Driver's choice.
   
Post #17992043rd Apr 2017 9:01 am
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garrycol
 


Member Since: 06 Dec 2010
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Australia 

Rock crawl, 1st gear low range - foot off the accelerator and with HDC on it will not kick in - in that configuration the torque converter is locked and you have full engine braking - on the steepest, slipperyest hills the car will go slower than with HDC alone. Plus you dont have all the racket and shuddering that HDC invokes.

You don't need HDC.
  
Post #17992083rd Apr 2017 9:36 am
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Reginald Molehusband
 


Member Since: 17 Nov 2009
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Scotland 2016 Discovery 4 3.0 TDV6 Landmark LE Auto ZanzibarDiscovery 4

On a steep, slippery descent, once you've lost grip and the speed of the vehicle exceeds the speed of the wheels you are by definition 'out of control.' To regain control the wheel speed has to match the vehicle speed and the quickest way to achieve that it to speed-up the wheels a little.

If you're relying on HDC this may be achieved using the + button, otherwise try a little accelerator. As soon as you are back in control you can work on slowing down again, but you can't do anything about speed and probably not much about direction whilst you are out of control.

It is one of the most counter-intuitive things to do in a car: going too fast so accelerate, but it does work if you can make yourself do it.

Of course, a proper recce before you start the descent could save a lot of embarassment. Whistle
 2016 D4 Landmark SDV6 (Euro6), Zanzibar (late run D4)
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Post #17992203rd Apr 2017 10:37 am
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Robbie
 


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United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Baltic BlueDiscovery 4

DSL wrote:
DrRobH wrote:
Pressing the brake will cancel HDC won't it?


No, it doesn't.


Yes it does, or at least you can consider it suspended. HDC is moderated by the right foot which may require some extra throttle to regain grip. HDC speed is controlled by gearing and the cruise buttons. For vehicles without cruise control the HDC can become self-defeating as the default speed may be too high for the conditions and people then start braking instead.

There are instructional videos on how it all works on youtube so worth a look.

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Post #17992233rd Apr 2017 10:47 am
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DG
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Reginald Molehusband wrote:

Of course, a proper recce before you start the descent could save a lot of embarassment. Whistle


yes ...and this Laughing Thumbs Up

TBF in my case someone had just gone (hurtled) down before me ... but poor comms signal meant that I heard a cracking, cutting out "don't come down" from the previous driver as " %$&%%$£ come down" Rolling with laughter
 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021  
Post #17992253rd Apr 2017 11:00 am
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DSL
Keeper of the wheelie bin 


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ISTR I'd seen Chris200100 go down with not a lot of control, decided to take the chicken route then saw you being supported by that tree. One of my better decisions. Whistle
   
Post #17992333rd Apr 2017 11:09 am
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DG
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Wales 

Slimer nearly lost it going down before me .... shining up the sloppy rainsodden mud smoothing my path Laughing
 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021  
Post #17992453rd Apr 2017 11:40 am
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DSL
Keeper of the wheelie bin 


Member Since: 11 May 2006
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Ukraine 

He could have taken the trees away. Would have made things even more interesting, as long as I wasn't at the bottom. Got some pics of the recovery operation, but no idea where. Embarassed
   
Post #17992473rd Apr 2017 11:43 am
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Hardware
 


Member Since: 28 Jun 2016
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United Kingdom 2011 Discovery 4 3.0 SDV6 XS Auto Sumatra BlackDiscovery 4

never knew that about the +/- buttons ... have to find a suitable hill to try it !
 .


Dean
====================================

2011 D4 XS - OBD port protection, RLD spare wheel protector, All LED interiors lights, Timed Climate enabled, iiD tool paired.
2011 D4 Landmark - Stolen from same dealer before I paid for it
2011 D4 GS - Stolen whilst at dealer Sad ... All LED interiors lights, DRLs, Spare Wheel protector.
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Post #17992633rd Apr 2017 12:03 pm
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Discologist
 


Member Since: 19 May 2014
Location: Yorkshire
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United Kingdom 2013 Discovery 4 3.0 SDV6 HSE Auto Orkney GreyDiscovery 4

DG wrote:
Reginald Molehusband wrote:

Of course, a proper recce before you start the descent could save a lot of embarassment. Whistle


yes ...and this Laughing Thumbs Up

TBF in my case someone had just gone (hurtled) down before me ... but poor comms signal meant that I heard a cracking, cutting out "don't come down" from the previous driver as " %$&%%$£ come down" Rolling with laughter
Ah, the Crimson Tide school of comms.  
Post #17994263rd Apr 2017 6:18 pm
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DSL
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Are we comparing DG with Gene Hackman? Shocked Shocked
   
Post #17994363rd Apr 2017 6:47 pm
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