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2010 2011 BMW 5 Series Forum F10 BMW 5-Series (F10) Forums General 5-Series Sedan and Wagon (F10 / F11) Forum Integral Active Steering (IAS) - Only seeing 1 degree movement, is my system faulty?
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      08-03-2019, 12:16 PM   #1
bendandthrow
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Integral Active Steering (IAS) - Only seeing 1 degree movement, is my system faulty?

My 2014 F11 has IAS. However I have to say that in the 3 months I have had the car I have never been aware of it. My previous car was a 2010 F11 and I can't say I have noticed any difference between them so far as low speed steering is concerned.

Out of idle curiosity today I tried to see by how much the rear wheels counter turn when manoeuvring slowly. I parked the car with full lock, got out and had a look. I could not perceive any angle to the rear wheel, whereas I expected a small amount of counter lock (as I had been driving slowly when turning the steering wheel).

I then stood outside the stationary car and turned the steering wheel full lock the other way whilst looking at the rear wheel. I did not see any movement of it at all. I did this several times and never saw the slightest movement of the rear wheel.

I then placed a large protractor like object up against the tyre whilst at full lock. Then I turned full lock the other way and lo and behold I saw a small gap appear of about 2mm. So 2mm at that point on the tyre is the full range of movement. The point on the tyre that I was measuring is at 11cm from the centre so is on a circle of pi x 11 x 2 = 69cm circumference. A movement of 2mm represents about 1 degree around the vertical axis of rotation.

From what I have read the rear wheel should turn by up to 3 degrees in each direction so I should have observed a change of 6 degrees or 12mm, or 6x what I actually observed.

Is this to be expected in this scenario or does it seem the system is under performing? It is hard to believe that a rotation of 1 degree is going to make a significant difference and so if this is normal it begs the question as to how worthwhile this expensive option is. There are no warning lights on the dashboard.

Thanks
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      08-03-2019, 02:05 PM   #2
wcr3d
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This may help explaining it.
"BMW's Integral Active Steering is a system available on some BMW models that uses a variable steering ratio with passively steered rear wheels, resulting in improved stability and comfort. The rear wheels can turn up to three degrees, depending on factors such as vehicle speed, wheel speed, and steering angle. Under 37 mph the system steers the rear wheels in the opposite direction as the front wheels, significantly reducing the turning circle and making for easier maneuvering during tight situations. Above 37 mph the system turns the rear wheels in the same direction as the front wheels allowing the vehicle to seemingly glide through corners and increasing comfort, especially for rear passengers. The system can also help keep the vehicle stable, especially when braking with each wheel on a different type of surface."
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      08-03-2019, 04:00 PM   #3
bendandthrow
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Quote:
Originally Posted by wcr3d View Post
This may help explaining it.
The rear wheels can turn up to three degrees, depending on factors such as vehicle speed, wheel speed, and steering angle. Under 37 mph the system steers the rear wheels in the opposite direction as the front wheels, significantly reducing the turning circle and making for easier maneuvering during tight situations."
Thanks, but I had seen this, particularly the bit quoted above.

I interpret "The rear wheels can turn up to three degrees" to mean 3 degrees in each direction, giving a total of 6 degrees lock to lock. Even if it is only 3 degrees lock to lock that is still 3x what I observed.

Others with this feature have extolled its virtues but I honestly can't tell I have it, hence wondering if it is working correctly. Which is why I tested it.
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      08-03-2019, 04:57 PM   #4
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Quote:
Originally Posted by bendandthrow View Post
Thanks, but I had seen this, particularly the bit quoted above.

I interpret "The rear wheels can turn up to three degrees" to mean 3 degrees in each direction, giving a total of 6 degrees lock to lock. Even if it is only 3 degrees lock to lock that is still 3x what I observed.

Others with this feature have extolled its virtues but I honestly can't tell I have it, hence wondering if it is working correctly. Which is why I tested it.
My last car had "passive" rear-wheel steering. It consisted of a collapsible bushing on the rear toe link. Removing the link made the otherwise secure rear wheel move about 1/2" in each direction. As it's passive there was no way to observe the wheel move, but it sure could be felt.

I don't konw how BMW does it, but if it's passive it may be the same type of system. I don't have it and haven't looked under at the rear suspension.

Just a thought, FWIW.
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      08-03-2019, 05:16 PM   #5
wcr3d
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Quote:
Originally Posted by bendandthrow View Post
Thanks, but I had seen this, particularly the bit quoted above.

I interpret "The rear wheels can turn up to three degrees" to mean 3 degrees in each direction, giving a total of 6 degrees lock to lock. Even if it is only 3 degrees lock to lock that is still 3x what I observed.

Others with this feature have extolled its virtues but I honestly can't tell I have it, hence wondering if it is working correctly. Which is why I tested it.
What you should interpret is the first sentence, key words being, CAN, UP TO, DEPENDING ON.
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      08-04-2019, 02:51 PM   #6
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Quote:
Originally Posted by bendandthrow View Post
My 2014 F11 has IAS. However I have to say that in the 3 months I have had the car I have never been aware of it. My previous car was a 2010 F11 and I can't say I have noticed any difference between them so far as low speed steering is concerned.
As you have experienced both standard and IAS systems, do you notice a difference with the (front) active steering? What about steering lock? IAS reduces lock by about 0.5 metres. "Lock to lock" is also much less than the standard EPS, reduced to about 2 turns at low speed.
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      08-04-2019, 04:26 PM   #7
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Quote:
Originally Posted by wcr3d View Post
What you should interpret is the first sentence, key words being, CAN, UP TO, DEPENDING ON.
Which part of this do you think I did not interpret correctly?

I am sure the intended meaning is that the maximum counter rotation of the rear wheels will occur at the lowest speeds (any rotation at high speed would be dangerous). And that maximum rotation should be 6 degrees, assuming the 3 degrees mentioned is from straight to full lock.

Mine only move by 1 degree.

Unless you think "upto" is used here as it is in broadband adverts and so varies from car to car...?
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      08-04-2019, 04:31 PM   #8
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Quote:
Originally Posted by HighlandPete View Post
As you have experienced both standard and IAS systems, do you notice a difference with the (front) active steering? What about steering lock? IAS reduces lock by about 0.5 metres. "Lock to lock" is also much less than the standard EPS, reduced to about 2 turns at low speed.
Yes, I think I can feel a difference in the front active steering. but hard to be sure now as its been a few months since I had my old car to compare to. I was surprised at how little I had to turn the wheel when performing the above tests.
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      08-04-2019, 06:01 PM   #9
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Quote:
Originally Posted by bendandthrow View Post
Which part of this do you think I did not interpret correctly?

I am sure the intended meaning is that the maximum counter rotation of the rear wheels will occur at the lowest speeds (any rotation at high speed would be dangerous). And that maximum rotation should be 6 degrees, assuming the 3 degrees mentioned is from straight to full lock.

Mine only move by 1 degree.

Unless you think "upto" is used here as it is in broadband adverts and so varies from car to car...?
You are wrong in at least my intent.
My intent is saying that unless you know the formula the computer uses you can't assume your guess is correct, that the maximum would occur at the lowest speed. That also using the key words that the formula is a running variable.
I also don't know what is so dangerous about higher speeds, though it clearly states the direction changes when over 37 mph.

I also have no clue what is meant by "broadband advert".
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