R65 rear spring rate?

[Barry]

Original BMW springs are  tighter wound at the top.  Can't think why it would matter which way up they are.  Spring rates remain the same.

[Allred]

I don't know if read this correctly or not, but you said that you bought shocks and springs from Bob's, did they arrive assembled, or did you have to install the springs on the shocks ?

Only reason I bring this up, is that if the springs are 'progressively' wound, the coils that are closer together should should be at the top .

 

The shocks and springs from Bob's BMW arrived assembled, and the tighter coils are at the top.  

I can't imagine why it would make a difference...does a spring know it is upside down or downside up?  Seems to me the "softer - wider" spaced coils would start to compress first, which-ever way they were installed.   :-/

But then, I'm no engineer...am I missing something here?  Would love to know

Allred

[Barry]

Dual rate springs have a number of coils closely spaced which will close up and become rigid thus reducing the number of active coils in the spring. Less coils means a stiffer spring or higher spring rate.  

For example original BMW fork springs are  dual rate with 66 coils of which 14 are closely spaced.
During the initial travel of the forks the spring has 66 active coils and a spring rate of 26.87 lb/in.  When the 14 closely spaced coils close up there are  55 active coils which gives a spring rate of 34.1 lb/in.

In theory dual rate springs have 2 distinct rates assuming all the closely spaced coils close up at the same time. In reality who can notice the change ?

Progressively wound springs have coil spacing which varies - well "progressively" which should result in a smooth transition  from the lower to the high spring rate.

It's much less obvious than with the fork springs but it seems to me that my original rear springs are dual rate rather than progressive and it's only during the last part of the suspension movement that the high rate comes in to effect.