[Bl@ckJ@ck]

In the new 2012 BMW 528i xDrive they add a new standard option, Hill Descent Control. Could anyone explain me how it works in comparison with regular break during going down hill? Does the Hill Descent Control use regular break or a special system? If we apply break too much going down hill, the break system will gonna fail due to overheat, so will this happen with Hill Descent Control?

And, after all, why Hill Descent Control is available ONLY for cars with xDrive, 4WD, AWD...?

Thank you!

[inny]

Originally Posted by Bl@ckJ@ck

And, after all, why Hill Descent Control is available ONLY for cars with xDrive, 4WD, AWD...?

I think you answered the question with a question (Well if you at least know the basics of xdrive and 4wd, awd)

HDC works at a pre-determined speed. Car does the breaking for you so you are focused on the steering and only steering if i remember well. (Speed cannot exceed 35km/h)

[Bl@ckJ@ck]

Thank you inny for the answer, but I'm a bit naive about technique and still not clear at the time. Hope you are patient to help me understand the problem

If HDC use the regular breaking system (just like we press on the break), so is the effect identical with using the break ourselves? I mean, assume that we're going a 10 miles steep down hill, and if we press the break excessively in that 10 miles, the break system is most likely going to fail due to overheat, right? So could the HDC fail the break system like this? (of course I guess no but if no, then HDC must use a different approach - and I want to understand about it).

For the second question, if HDC just use the regular break system to slow down the car, so it could also use the same technique in RWD (or even FWD) car as well (because RWD or FWD cars also have break system with ABS, Break Assist...). If this is not true then there must be something that 4WD/AWD has over RWD/FWD so that HDC can be installed only in 4WD/AWD. With my limited understanding about cars, at very basics, 4WD/AWD is different from RWD/FWD in the manner that it has additional drive wheels that push the car, additional drive shafts and differentials. So which of these make HDC possible ONLY in 4WD/AWD cars?

[inny]

I would gladly help you if I extensively knew the technical/mechanical part but...

Without knowing much but only from what I read about it and my common sense:

HDC is using breaking system along with ABS. It is much needed from driving rules and so on that when driving downhill to have low gear (preferably 1st gear) in order to avoid using the break and consequently avoid overheat which might result to breaking system failure. If you use the breaking system yourself while HDC is active it overrides the operation of HDC.

I can only say for the second part that 4wd/awd is more control of the car in this situation. If abs can detect any of the 4 wheels accelerating or decelerating too fast this makes this system work as it "should" on the specific types of vehicle.

All the above said while having in mind that there's enough traction.

[Bl@ckJ@ck]

Hi thanks again, so it seems that HDC just does the break for us, and we're still in charge of selecting low gear and be aware of the overheated breaking failure risk. With this understanding I think it would be preferred going down hill by ourselves by selecting suitable gears to avoid excessively breaking and get out of the risk.

HDC uses some traction control found only in 4WD/AWD, so in case of RWD/FWD I think it's nice if they provide a break overheated waring system or something similar so that it is safer going down hill with these cars.