Why does PASM not have variable spring rates?

[Mario149]

I just discovered that BMW bikes with ESA II (electronic suspension management) have the ability, amongst other suspension trickery they do, to adjust the spring rates of the springs as well as the damping in the shocks when switching between comfort, normal and sport modes. PASM only changes the damping meaning that the spring choice is always a compromise for Normal and/or Sport modes

If BMW can do it on something as small as a motorbike, how come Porsche haven't done it on their cars?! BMW have had it since 2009 I think.

[foxsasha]

I think you'll find the bikes adjust spring preload which adjusts ride height and sag (mainly used to accommodate the extra weight added by a pillion and or luggage), not spring rate.

[Magic919]

That must be why the BMW is so much better to drive.

[Mario149]

foxsasha said:

I think you'll find the bikes adjust spring preload which adjusts ride height and sag (mainly used to accommodate the extra weight added by a pillion and or luggage), not spring rate.

Def adjusts Spring rate as far as I can tell, 3rd para here:

http://www.bmwmotorcycles.com/com/en/index.html?co...

[foxsasha]

Mario149 said:

Def adjusts Spring rate as far as I can tell, 3rd para here:

http://www.bmwmotorcycles.com/com/en/index.html?co...

'This system, which is unique within the motorcycle market, allows the driver to adjust both the rebound-stage damping of the front and rear spring struts and the spring mount ("spring preload") of the rear spring strut, but also its spring rates and therefore the hardness of the spring by electronic means.'

I stand corrected. Every day's a school day