Re: E30 Suspension Changes

[Randy Walters <randylwalters@xxxxxxxxxxxxx>]

Kenneth Hillers <kjhillers@domain.elided> wrote:

>I have a 87 325i in great shape with 125k miles. I started to change and
>upgrade some suspension components and that's where the fun/problems began.
>The car is stock except for installed HD Bilsteins that have 100k on them
>
>1.     I first upgraded the stock sway bars to Eibach (22mm F, 16mm R) and
>replaced the front factory sway bar links with BMP sway bar links.
>
>3.     This next upgrade is where my problems begin. I replaced the stock
>springs with Eibach springs that lowered the car 1" to a 1-1/2". The car looks
>really aggressive but is way too harsh over some tar strips and bottoms out
>even going into my drive way. Over certain bumps or undulations in the road
>you get that sick "pothole" response. The steering wheel is slightly off to
>the left but does not pull to the left.
>
>Obviously the lack of suspension travel is creating the above problems, but I
>did not think that they would be as extreme. Is the problem compounded by
>having the wrong shocks for the spring i. e. Bilstein sport shocks should be
>used or perhaps an adjustable shock as Koni to better match the shock to the
>spring? Would M3 springs have been better to use? Since I only use the car for
>the street, I'm leaning to putting back the stock springs and adjusting the
>sway bars to the stiffest setting.
>Any help in this matter would be greatly appreciated!
>Ken Hiller   Freehold NJ

 The problem is that you used Bilstein Heavy Duty shocks with Lowering Springs
plain and simple.  The shocks are being forced to ride very near their internal
bumpstops and any quick input immediately bottoms the shock out.  This has
happened to a lot of E30 owners who've used HDs with shorter springs.  The
two simply do not work well together at all.

 Also,  do not use stock springs with the larger swaybars !!  Doing so
will place too much load on the swaybar mounting points and will
almost assuredly cause them to break.  Use stiffer springs to reduce
body roll first,  then use swaybars to fine tune the handling. They're
not big enough anyway to do much for body lean on these heavy
cars anyway. I've found that stiffer springs do much more for reducing
body roll than larger swaybars.

 There's nothing wrong with using Eibach Lowering springs as long as you
use a shorter shock,  or one that compresses more than the stock or HD
shocks do.  Even though the Eibachs (and H&R Sport) springs are much
stiffer than stock, the heft of the E30 can still compress them deeply and
will bottom an HD shock out easily.  Even if you use stock E30 M3 springs,
they'll still cause Bilstein HDs to bottom out on their internal bumpstops.
Scott Miller (90 325is) was using E30 M3 springs with Bilstein HDs and
had a big problem with constant bottoming (even when crawling over
speed bumps at 1 mph) so he installed Bilstein Sports up front and
the problem went completely away.  And in your case the Eibachs
lower the car an additional 3/4" to 1" beyond E30 M3 springs so i
imagine your bottoming problem is pretty severe.

 You'll simply have to get shorter shocks, and while you're at it i'd go
with Koni adjustables instead of the shorter Bilstein Sport shocks.  I've
found that Bilsteins aren't well suited to stiffer E30 springs due to their
lack of adequate rebound damping, but the Konis will do a much better
job of controlling the rebound caused by the stiffer springs.  The Konis
compress about as much as the Bilstein Sports and neither of these will
bottom out except maybe in extreme circumstances.  And the added ability
to adjust (increase) the rebound settings on the Konis comes in really
handy with the stiffer springs :-)

Randy Walters
89 325is
(has had many suspension setups during it's modest development)

http://community.webshots.com/user/randywalters

PS:  If you haven't been to the BMW E30 Network Message Board,
you should check it out.  It's where all the E30 gurus are hiding :-)

http://forum.bmwe30.net/index.cgi



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