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      11-29-2012, 12:46 PM   #48
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Drives: BMW F11 535i Touring
Join Date: Mar 2007
Location: Scotland, Highland Region

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Originally Posted by F30FAN View Post
I note this debate has been raging for a while and its been a ping pong from one extreme point of view to the other...

The thing is gentlemen like most things in life it boils down to personal preference, from make, model, colour and options it is down to individual choice/taste.
It certainly is down to user choice and perceptions, even if we debate the technical aspects of it all day long.

MaestroAl and I see it from totally opposite poles. I tend to assess it the same as BMW do, and as directed to similar performance as the variable steering systems fitted to their 'sporty' models like the M-cars, (albeit in hydraulic form), or the F20 M135i as the VSS version of EPS.

What I don't see from the 'loose' data which BMW are putting in the advertising blurb, that it is 100 degrees before there is any change in ratio, they simply state:

In the case of smaller steering angles between zero and 100 degrees, the BMW 3 Series displays accurate tracking and high stability on straight stretches while conducting steering movements with impressive precision.
That statement does not definitely state the ratio is constant to 100-degrees. It doesn't even state whether it is 0 - 100 degrees in either direction, or an included angle. Can be read several ways. The typical way a variable ratio rack is geared is as set out in the graph I attach. The graph that we would need to reflect a 0 - 100 degree 'constant' ratio would be very unusual indeed, nothing like the typical form we would see for any variable steering system that is intended to make the car more agile.

I'd love to see the actual form for the variable sport racks that BMW are using, but BMW are not giving too much away, anymore than they do for the variable ratios in the M-cars. Even in their detailed technical data, they just state an overall average ratio. Plus the lock to lock figures.

For the BMW F10 M5 this is all that is stated in BMW data.

M rack and pinion power steering gear with variable ratio, standard with Servotronic. The average overall ratio is 13.05:1 for 2.6 steering wheel turns lock-to-lock compared to 17.1:1 and 3.0 with the F10.
I doubt anyone would question the integrity of BMW in offering and fitting the 'M rack' to the M5 or M3, or even the VSS system in the F20 M135i. Saying that it isn't hardly worth having, even suggesting the reduced 'lock to lock' just helps parking.

But each to his own, not everyone sees the value in an M-car either. A lot of money for a car that is 'nearly the same' as the standard models.