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View Full Version : Turning Circle for cars with Integral Active Steering


KCComp
10-08-2010, 01:33 AM
The only turning circle data for the F10 is in the non-ix online manual, which states 12m.

When I test drove a 550i (without Integral Active Steering) it definitely did not seem like 12m/39.4 ft. On the 3 series, the turning circle difference between RWD and AWD is close to 3 feet as I recall. The car I drove really felt like 36-37 feet instead of 39.4 feet.

Perhaps they are listing the worst-case turning circle, for the AWD ix?

And certainly the rear-wheel steering of the Integral Active Steering, moving 2.5 degrees in oppposite direction at low speeds, must improve the turning circle over standard. Has anybody seen any stats on that?

pharding
10-08-2010, 04:20 AM
The turning radius with Integral Active Steering on the F10 is superb. I was surprised at how tight it was when making my first U-Turn over my prior E60 with Integral Active Steering.

DavidNJ
07-22-2013, 05:19 PM
The documentation, limited, hard to find, and dated, says it makes a 1.6ft difference. my calculations indicate it should be on the order of 1.6 meters. Since marketing people frequently make mistakes (e.g, try to get a TFSI stratified charge engine in the US, not possible) this could easily be one. It would be great if someone could actually take the measurement. If not in the US, IAS is popular in Hong Kong, Singapore, and I would guess Tokyo and other Japanese cities.

K-A
07-22-2013, 06:42 PM
All I know is that my car has a terrible turning radius.

dbs600
07-22-2013, 09:42 PM
All I know is that my car has a terrible turning radius.

And mine far worse... :thumbdwn:

DavidNJ
07-23-2013, 12:25 AM
And mine far worse... :thumbdwn:

Autoweek had a 760Li test today, IAS, DDC, and ARS are standard.

Comments:

"The chassis balance felt near perfect to me. I'd almost call the car nimble; as nimble as 5,000 pounds of metal can be anyway."

http://www.autoweek.com/article/20130722/carreviews/130719803#ixzz2ZqZJ5400

Motor Trend had a comparison test that included a 740i with IAS a while ago. They also called that car nimble.

Net, IAS does seem to work.

Audi has "Dynamic Steering" as part of a sport package on several models. It has the variable ratio, but not the rear wheels steering. Porsche has the rear wheel steering on some 911 models. Infiniti has had both, but the front steering ratio was fixed after it was selected. The 2014 Q50 has the front part only.

If it was available on the M5/M6 and 535x we would probably here more about it. But it isn't compatible with the hydraulic steering.

If my calculations are correct, it reduces the turning circle on the 5-series from 39ft (12m) to around 34ft. That would be a very significant difference and it would be great if someone could confirm that.

dbs600
07-23-2013, 05:06 AM
Why can't they engineer better steering to begin with (i.e.: MB S-Class)?

IAS is great, but complex and $ to align, and I suppose to repair...

DavidNJ
07-23-2013, 09:56 AM
Why can't they engineer better steering to begin with (i.e.: MB S-Class)?

IAS is great, but complex and $ to align, and I suppose to repair...

What does the S-class do? I thought is was straight up vanilla steering with a variable ratio; that is the ratio varies depending on how far the steering wheels is turned, not dependent on what the car is doing.

The S-class has torque vectoring which the BMWs don't seem to have (Audi and Porsche also have it). BMW uses IAS or xDrive for a similar effect to torque vectoring.

Is IAS more expensive to align? I would have thought the computer has a setting to hold the wheels straight for alignment.

DavidNJ
07-23-2013, 10:34 AM
Two videos:

Audi Dynamic Steering (silent, on an A4):

http://www.youtube.com/watch?v=umsULUG2P-M

Porsche rear wheel steering (overdone video, on a current GT3):

http://www.youtube.com/watch?v=cqRIczkBgJI

dbs600
07-23-2013, 09:37 PM
What does the S-class do?

Not apples to apples, but my 1994 S500 Sedan turns on a dime!

Not sure of the tech, but believe it's good old-fashioned engineering.

ausdude
07-23-2013, 09:46 PM
My E30 and E46 turn on a dime. My former CL600 turned great too. My F10 has a horrible turning radius

DavidNJ
07-23-2013, 09:57 PM
Not apples to apples, but my 1994 S500 Sedan turns on a dime!

Not sure of the tech, but believe it's good old-fashioned engineering.

That S-lass was too new...try real "good old-fashioned engineering"

http://www.bimmerfest.com/forums/attachment.php?attachmentid=388237&stc=1&d=1374638195

Blkthght
07-24-2013, 01:09 PM
550i with IAS. Excellent turning radius.....far better than my much smaller honda accord. I actually get a kick out of making tight u-turns and watching the cars behind me have to resort to a 3pt turn.

ae86pwr
07-24-2013, 01:20 PM
traction off ... a lot of throttle ... problem solved.

DavidNJ
07-25-2013, 05:14 PM
550i with IAS. Excellent turning radius.....far better than my much smaller honda accord. I actually get a kick out of making tight u-turns and watching the cars behind me have to resort to a 3pt turn.

Have you actually measured it? My calculations estimate around 33.5 ft. That would be very tight indeed.

The number of cars with variable steering ratios via gearbox (compared to a variable ratio rack) are high: Audi, BMW, Lexus, Infiniti. Porsche and Infiniti also have rear wheel steering. BMW and Infiniti are the only ones who combine them.

How is the steering feel and general on-road handling?

ae86pwr, nice picture...S2000s on a race track. Are you an S2000 fan? I had a 2000 and now a 2004. I nearly bought on the last year they made it...but didn't. Maybe a mistake...the last year was nice.