During my off-road adventures last summer I had the opportunity to try out the Hill Descent Control quite often. The way this electronic help works seems me to be rather bumpy. As it uses the ABS system, that controls the slipping of each wheel independently as well, I wonder what the advantages or disadvantages are compared with "normal" braking. (except for the automatically monitored low speed of course).

In order to explain my question better: a steep descending off-road track is mostly very irregular. This means that the fixed descending speed of 7 Km/h sometimes is too slow and a few meters further much too fast. In real terms this means you have no other choise than operating the brake pedal yourself. Does this heat up or wear out the brake pads faster ? And is H.D.C. more efficient in very extreme situations ?

you can always press the speed increase button on the cruise control to increase your speed whilst using HDC.

A very small increase in speed for each time you press the button

I know npinks but that doesn't answer my question. When there's a deep well in the track, you have to proceed at almost no speed...

I asked this very question of the instructor on my LR Experience drive last Saturday.

His reply was let HDC does as much of the work as possible; if you want to speed up for a short distance use the gas pedal, as soon as you ease off the pedal HDC will bring you back down to speed (probably easier than adjusting the HDC from cruise control for short distances). If you want to travel slower than HDC then yes apply the brakes to override HDC.

As for brake heat and wear then any applicaiton of the brakes is converting kinetic energy (of the car moving)into heat; I would suggest that whether the brakes are applied by HDC or by the the brake pedal will not have a great effect on wear and heat generation; that will be a function of speed.

My experience of HDC is that the sound generated when it operates tends to be quite noticeable, but in terms of vehicle movement and control my perception is that it is smooth and controls the vehicle very well.

I agree avtur but as far as I know H.D.C. seems to be not much more than a gimmick for inattentive or worthless drivers.

Paul wrote:

I agree avtur but as far as I know H.D.C. seems to be not much more than a gimmick for inattentive or worthless drivers.

You know me so well

As far as I was aware, this is much better than just braking. HDC senses each wheel, so if one loses contact, it is the one that is braked, and not the others.

If you were using the brake, you'd run the risk of all 4 losing contact with the ground, whereas with HDC, you stand a much greater chance of getting down the hil, under control.

I agree that 3mph can feel a little too quick at times, but I would much rather it went too clow the other times, and as was said, at least you can change it now, and it isn't the 6mph it used to be on the old freelander.

Rich

rmbillington wrote:

As far as I was aware, this is much better than just braking. HDC senses each wheel, so if one loses contact, it is the one that is braked, and not the others.

Rich

The point of HDC is to compensate in part for the lack of a low ratio gearbox on the FL2. As any experienced off-road driver will know the way to descend a sleep slope is in first gear, feet off all the pedals. Braking manually is a no-no as you will skid, potentially stall (if it's a manual) and possibly lose control, HDC reacts far quicker than a human and more intelligently than ABS as it is operating in conjuction with Terrain Response to control brakes on 4 wheels independantly along with the centre diff-lock (haldex) unit. If you push the brake pedal you are applying brake effect to all four wheels (front biased) and if you skid you will not actually slow down so you can't control the speed. HDC keeps the car in control at a safe descent speed, use it!!!

Cotefarmboy, this is more or less word for word what the official LR brochures say but it doesn't help me any further. ABS works on the 4 wheels independently as well (at least if it's a 4 channel ABS) but in difficult terrain I was surprised by the difference between "normal" braking and the H.D.C. assisted braking. Descending with H.D.C. you hear a quick succession of short skidding noices. "Very short" as the electronic help releases the breaking pressure when it detects skidding. If you descend the same road at the same speed but with H.D.C. disactivated, it takes much longer before the ABS comes in but eventually, of course it works perfectly off-road as well if the road is slippery and/or steep enough.

I've got the impression that H.D.C. works less smoothly than A.B.S. When H.D.C. is switched on, the initial braking pressure is very high, causing wheels to skid so it has to interfere continuously by releasing braking pressure.
If you use the brakes without H.D.C. in a sensitive way, you avoid too hard braking.
At least, that's what I suppose is happening. Please tell me if I'm wrong.


And by the way: of course you should descend in first gear. H.D.C. activates this automatically but someone who doesn't know this should stay away from any hills or mountains even when he never goes off-road.

Then I guess it is down to personal preference, I rarely use HDC in the Disco 3 but I have low range 1st, if you prefer to brake manually and are confident with this then so be it. With my old FL1 I found the noise from the HDC was the ABS pulsing very fast rather than the car skidding.

I have minimal, minimal experience of off roading and follow cotefarmboys lead on this!! If you are a complete novice on 4x4 you will engage HDC. If you know what you are doing you may find 'personal' brake activation your best solution. Again, as cotefarmboy states, if offroading is your main ambition then the Disco3 with low range is the real answer, lets be honest how many of us with FL2's REALLY, honestly REALLY will use them offroad Its a bit like asking who wears underwear s, m or l (small, medium or liar ) personally I am liar so the wife says, but she is very sympathetic
If you need help using HDC,.. use it...if you feel you can do better without, thats fine..go for it!!

nice reply carlfraz but it doesn't really give much explanation I'm afraid.

Paul

I don't know how much more of an explanation you need buddy, the key difference is that HDC allows the car to slowly descend a hill at a safe speed with minimal risk of skid, if you rely on brakes/ABS you don't have the fine control, sure ABS will activate but only when a wheel locks and you have theoretically started to lose control which is dangerous off-road. HDC does it's upmost to keep the car wheels rolling and therefore in contact and in control. HDC does not lock the wheels then use ABS, it pulses the braking slowly so you don't lock the wheels.