Interessanti notizie sul nuovo ESA, sembra risolto il problema della durezza della molla con un elastomero aggiuntivo.(parte in grassetto).
Sembra che, contemporaneamente al precarico della molla, il sistema vari anche la durezza del sistema quindi il suo k.
Ci Vorrebbe però un volontario traduttore.(io sono un po' approssimativo).
Fonte:
http://hellforleathermagazine.com/20...nica.html#more
Details: BMW ESA II electronically adjustable suspension
BMW's ESA II suspension -- available on the K1300S, K1300R and K1300GT -- is the first in the world to offer an adjustable spring rate. In addition to that spring rate -- the amount of force it takes to compress the spring or its "hardness" -- ESA II can alter preload and offers on-the-fly adjustment of the compression and rebound damping; basically, you can fully adjust your suspension at the touch of a button to a greater degree than ever thought possible. But how does it work?
On previous suspension units, adjusting the spring rate -- thus providing equal handling no matter the weight carried by the motorcycle -- was only possible by stripping down a shock and replacing its spring for one of a different weight. BMW gets around this by adding a polyurethane bushing to the top of the spring, meaning suspension movement basically passes through two springs; the actual spring and the bushing. By altering the rate at which that polyurethane compresses, BMW is able to alter the effective overall spring rate.
Of course, it's not that simple. In order to precisely control the rate at which the special polyurethane material -- called 'Elastogran' -- compresses and expands, BMW contains it within a sleeve located around the shock's damper unit. An inner collar slides up and down in the space the Elastogran expands into under compression, reducing that space to make the force required to compress it greater or increasing the space to make the required force less. That collar is actuated by ESA II's computer and moves through three positions based on settings chosen by the rider.
Those three settings are: "Solo," "Solo with Luggage" and "With Passenger and Luggage." All three are represented by symbols in the instrument panel rather than awkward phrases and are only adjustable while the machine is stationary. These settings also control the amount of preload, or the amount of force required to initiate spring compression, which effectively alters the ride height.
In addition to those three, there's also settings for "Normal," "Sports" and "Comfort" modes, which alter the rebound and compression damping rates. BMW claims that ESA II offers a greater degree of adjustability to damping settings than its previous system.
The latter set of three settings is adjustable on the move and also affects the spring rate, which will be automatically adjusted to suit the chosen performance parameters.
The degree to which the shocks are adjustable varies front to rear (remember that the K-Series range uses Paralever front suspension), it appears that the front spring rate is adjustable only while stationary.