Trailer Stability Control

I am posting this here even though it is for the new X3. It's interesting to see how BMW is adding additional features to the DSC system. Wonder what's next???

A unique BMW feature: trailer stability control.
Featuring BMW’s innovative trailer stability control, the X3 is ideally suited as a comfortable, safe and high-traction vehicle for towing a trailer. This system offers additional safety against the dangerous risk of instability building up to generate an uncontrolled swerving effect possibly leading to an accident. And it is important to note in this context that the X3 2.5i is able to tow a trailer of up to 1,800 kg (3,969 lb), the two three-litre versions even being able to handle 2,000 kg (4,410 lb).

In terms of driving dynamics, any vehicle towing a trailer is subject to a relatively significant risk of body roll or sway, such pendulum action increasing as a function of speed. A heavy trailer may indeed cause a significant risk even at low speeds, the trailer and the vehicle itself, once swaying, no longer being able to regain their stability unless a control system intervenes right away.

Trailer stability control recognises such dangerous swaying motion immediately and quickly slows down the vehicle, applying the brakes also on the trailer to reinstate vehicle and trailer stability and once again build up safe driving conditions. The control unit “recognises” that a trailer has been hooked up as soon as the power supply has been connected to the car, thus being activated and serving to intervene as of a speed of 65 km/h (40 mph).

This control function is based on constant supervision of the yaw rate signal informing the DSC control unit of any rotating movement of the vehicle. With this signal being permanently supervised, any pendulum motion is recognised by the typical course of the signal detected by the control unit. Then, as soon as the signal exceeds a certain limit, brake pressure is built up on all four wheels, providing 2.5–4 m/sec2 of stopping power without any intervention on the part of the driver. At the same time engine power is briefly reduced to a minimum, the rapid reduction in speed ensured in this way stabilising the vehicle and the trailer very quickly and efficiently.

Activation of trailer stability control is displayed by the DSC/xDrive telltale light flashing on and off. Being part of DSC Dynamic Stability Control, trailer stability control is automatically deactivated as soon as the driver deactivates DSC.

LOL, since X5 and X3 aren't designed to haul trailers (or go off-road), the only safety feature that I can think of that's needed is some sort of DSC-related sensor that accounts for swaying left/right while yapping on the cell phone. It would detect the driver's level of indifference, and counteract the swerving that would normally happen in these siutations.

ff, why aren't the X5 and the X3 designed to haul a trailer in your opinion? I tow a trailer with all my tools and track trailers, weighing a total of over 650 pounds, with my E46 at high speeds, with no problems whatsoever. I also know Jon Shafer tows his dirt bikes with his E39 with no problems, so I'm confused as to why the X5 or X3 couldn't do the same?

I think this trailer stability control is a great feature.

X5 is rated to tow 6,000lbs.

That is pretty good

Originally Posted by DougDogs

I know that the transmission shifting profile is changed automaticly when you plug a trailer into the X5. I wonder if the X3 transmission software will also re-map when a trailer is attached.

I assume that is if it has the factory hitch, correct?

Doug- I know you have a boat as well, but not sure if you trailer it?
I was always under the impression that if you experienced trailer swag then the best thing to do would be to speed up. Interesting that the BMW system applies brakes to solve the problem.

Another point to consider is that most boat trailers use surge brakes and not electric brakes so I wonder how the system would work, or if it would work at all.

Originally Posted by FireFly

I was always under the impression that if you experienced trailer swag then the best thing to do would be to speed up. Interesting that the BMW system applies brakes to solve the problem.

Yeah, but can you imagine the safety (i.e., lawsuit) implications
for a system that automatically accelerates the car? Presumably BMW learned something from Audi.

Originally Posted by DougDogs

I scratched my head about that one also. I do trailer my boat a few times each year. (this year, the only times I put it on the trailer was to avoid 2.79 a gallon gas prices on my lake ) I haven't encountered trailer swag with my trailblazer, but I used to have one of those 2 door blazer S10's to tow my boat. I never felt comfortable going above 50 mph in the S10 cause it was too small. It was pretty easy to get swag "going" with the S10. It is about the hardest thing to make your foot do, but the best thing is to hit the gas, get control, then lift off the gas. My boat and trailer were almost 2 times as long as the S10. The S10 was geared for towing the weight, but could not deal with the length to good.

I paid too much money for my boat, trailer, and tow vehicle to hit the brakes. (I enjoy living, too)

I was interested in the X3, (when lease is over on the trailblazer) before the towing weights were announced. 4400 lbs is a little too close to my boat/trailer weight if my gas tanks are full.

Toureg is looking better and better or maybe a CPO X5

Toureg is one of the best, if not the best, looking SUV's on the market. I'm very impressed with them. How about a 2003 X5? They are offering deep discounts if you can find one.

Let me know how the X3 handles the towing. I have a somewhat unusual set up where I tow the boat to the marina and leave it on the trailer for the summer. When I want to use the boat, I use the ramp at the marina. So towing back and forth is not an issue for me.

My wife has a business trip planned for Munich in May so I am thinking ED on the X3 - it will actually be my wife's car to replace her Exploder.

I read that the X3 handles/drives better than the 3 series Sedan. Wonder if it's marketing hype??? If it's true, it may be time to trade in the xi for the X3 and have 2 in the family