pjgraham86
Member Since: 18 May 2009
Location: Glasgow
Posts: 227
  
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| Cruise control - downhill? |
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The cruise control on our MY D4 XS does not hold the car at the set speed when going downhill. I realised this the other day for the first time when I set the speed at 32mph and as I went down a hill, it gradually crept up to 47 (thankws fully I had moved from a 30mph limit to a 50mph limit by then).
This surely can't be right. Our other car's CC brakes the car as required when going downhill to maintain the set speed.
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 10th Jul 2012 1:04 pm |
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B16 KJR
Member Since: 10 Jul 2006
Location: Rosyth, Fife
Posts: 3005
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I don't think the cruise control is linked to the brakes at all, might be wrong though 
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| 10th Jul 2012 2:15 pm |
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WINDSWEPTISLANDER
Member Since: 21 Jul 2011
Location: Way up north
Posts: 523
 
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not linked on mine so far as I'm aware, never driven a car that is.
Sorry, just noticed you're a D4 
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| 10th Jul 2012 2:16 pm |
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Ted Newman
Member Since: 09 Oct 2010
Location: SE London
Posts: 840
 
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Our 2011 D4 does not link CC to brakes - shuts off fuel yes but no brakes. LR Discovery 4 XS pulling an Airstream 532 Caravan also own (since new) a 1996 MGF
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| 10th Jul 2012 2:22 pm |
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B16 KJR
Member Since: 10 Jul 2006
Location: Rosyth, Fife
Posts: 3005
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Think its only cars with ACC that are linked to the brakes 
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| 10th Jul 2012 2:29 pm |
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jwargyll
Member Since: 01 May 2010
Location: Argyll
Posts: 20
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not linked on my D4 XS neither. Can't recall any car I've had with CC doing any "intelligent" braking. BTW...it's the big fat pedal in the middle of the driver's floorwell!
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| 10th Jul 2012 2:33 pm |
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M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8243
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Once had a Merc ML that changed down to use the engine for braking if the speed was exceeded, would not recomend the car though. It can when others can't,
It will when others won't,
It goes where others don't.
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| 10th Jul 2012 2:52 pm |
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APL
Member Since: 14 Sep 2011
Location: Europe
Posts: 1130
 
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This is interesting. I've got CC on mine which of course is a 6-speed manual. Now I've not used it an awful lot, mainly because of the lack of suitable roads here to use it on, but I am sure that when I did use it on the M4 in the UK once, back when it was new, it used braking on downhill sections, because as soon as you press the brakes it cancels the CC.......? 2016 Discovery 4 Commercial
2019 Discovery 5 HSE
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| 11th Jul 2012 9:32 am |
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M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8243
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Cc is cancelled on all models when the brakes are used.
Once had a Merc slk 350 that didn't, the cc would not disengage  The harder I pressed the brake the car thought it was going uphill and changed down with more power I had to turn the engine off which locked the steering I ended up in a ditch in a field  apparently it had a fault on the accelerator potentiometer. It can when others can't,
It will when others won't,
It goes where others don't.
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| 11th Jul 2012 9:53 am |
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pjgraham86
Member Since: 18 May 2009
Location: Glasgow
Posts: 227
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Thanks for replies - clearly it's not a fault and I'll need to brake for myself, which is probably intuitive anyway when going downhill.
Oddly in light of M3's post, my other car is currently a Merc SLK350 and it DOES brake when in CC going downhill.
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| 11th Jul 2012 12:17 pm |
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jamieg7762
Member Since: 05 Mar 2010
Location: Warwickshire
Posts: 1232
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Isnt the merc linked into the speed limiter on the SLK, I am pretty sure mine was on the 230 that I had.
I thought it was the same on all cars, that only cars with a speed limiter braked when they went above the set speed. d4 HSE in Corris Grey with Black options pack
D3 with the following
Alive Tuning EGR blanking kit
Alive Tuning Re-map
Alive Atrics console
Samco intercooler hoses (from Alive Tuning)
Alive Tuning De-Cat pipe, lovely tone!
Retrofit OEM Hybrid TV tuner
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| 11th Jul 2012 12:29 pm |
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Navigator
Member Since: 17 Mar 2010
Location: Stay at Home. One of the lives you save could be your own.
Posts: 5113
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Some folk knock it into neutral on the downhill bits and save fuel. A vaccine does not stop you catching a virus, or passing it on, or getting ill from it, really ill. It does reduce the likelyhood of you dying when really, really ill. Stay Alive - KEEP AWAY FROM PEOPLE.
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| 11th Jul 2012 12:34 pm |
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mig31
Member Since: 26 Oct 2009
Location: Reus
Posts: 64
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Hi pjgraham86,
I use my CC quite often while I'm driving downhill on alpine and pyrenees motorways.
It's not at 35 mph (more like 60-70) but I simply put the gear in commandshift and drop a gear (or two).
That's how I've been taught, to use engine breaking instead of brakes.
I can't really give you the exact speed, but I'm perfectly sure that in 4th gear I'm perfectly able to maintain 110 kph on the motorway with CC.
Just for your info, this is on "decent" slopes which have emergency runaway lanes for trucks/cars with brake problems.
Always worked a treat!
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| 12th Jul 2012 4:02 pm |
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Gareth
Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26779
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Now it may be just a D3 thing, but I am sure my D3 dropped a gear automatically when descending a long hill on cruise control. It was on the A75 heading down towards the coast, it was a pretty steep and very long descent, and I was towing a caravan. I had the CC set to 60 ish.
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| 12th Jul 2012 4:40 pm |
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DSL
Keeper of the wheelie bin
Member Since: 11 May 2006
Location: Off again! :-)
Posts: 73121
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| Re: Cruise control - downhill? |
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pjgraham86 wrote:Our other car's CC brakes the car as required when going downhill to maintain the set speed.
Your other car isn't a BM is it? Mine uses the brakes to maintain the set speed going down hill.
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| 12th Jul 2012 4:46 pm |
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