Re: HD or sport?

[Mike Klein <klein@xxxxxxxxxxxxx>]

> Date: Sun, 29 Nov 1998 19:08:21, -0500
> From: NLNR36B@domain.elided (MR JASON R MCCOWAN)
> Subject: Re: HD or sport?
> 
> >well, to get to the point, when i had the stock shocks off, i 
> compared them
> >to the bilsteins, and they were a bit longer than my stock ones, hum.
> ..
> >interesting, so then when i installed both of them on and when i 
> took the
> >car off the jack stands they raised my car!! should the shocks do 
> that?? 
> 
> It's probably because the Bilstein Sports are stiffer, therefore not 
> compressing as much with the car's weight on them.  
> 
> Later,
> 
> Jason McCowan
> NCC

"Stiffness" of a shock has nothing to do with height of the car.  There is no
spring rate associated with a shock, even a high pressure gas shock.  Stiffness
of a shock describes the damping factor, which has no effect on the height of
the car or the shock's compress.  A stiff shock compresses exactly as much as a
soft shock with the same weight on it; it just takes more energy to get there.

However, as m6bigdog@domain.elided ably explained, high-pressure gas shocks (of
which Bilsteins are one example) will add an offset to your height.  They push
their two halves apart with a certain constant force from the gas pressure,
which raises the car a static amount until compensated by the suspension's
springs.  This force doesn't affect spring rate because it is a constant force,
irrespective of position.  A spring's force is proportional to position.

As far as HD vs. Sport, I highly recommend calling Bilstein directly (1-800
number is on their Web Site), and ask for the Motorsports Division and talk to
someone knowledgeable about BMWs.  I was in a similar situation a while back on
my 911, and the basic guidance from Bilstein is that HDs are tuned to the stock
suspension and are the better choice if you are staying stock and are not
looking for ultimate handling.  However if you have, or are planning to have, a
stiffer suspension *and* you would like to take a few 1/10's off your lap
times, Sports are the choice.  I picked HDs which for my daily commute are
*plenty* stiff and work superbly on non-competitive track events that I like to
do.

		-Mike
		klein@domain.elided

'98 323iC, 2.5k, Avus Blue
'87 911 Carrera, 85k, Venetian Blue

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