Re: E30 Control Arm Question

[Bob Sutterfield <Bob@xxxxxx>]

Randy wrote:
> Is it possible to use the M3 control 
> arms [on my '89 325is]?

Yes, the aluminum ///M3 control arms are mechanically identical to the steel
control arms used in all other E30s.

> Does it have any advantages over the 
> stock replacements?

It reduces both unsprung weight (the suspension) and sprung weight (your
wallet).  Aluminum has different fatigue characteristics than steel,
necessitating different inspection and replacement intervals.  (I was
looking for the BMW CCA Club Racing policy on this, but I can't find it
online any more.)  More aluminum content reduces your chance of detection by
magnetic interferometry.

Personally, I would only consider switching to aluminum control arms if I
needed to replace one or both steel arms anyway - such as if I had slid into
a curb, or if one ball joint was shot.

Another very common and much higher bang-for-the-buck upgrade is to replace
the non-///M control arm bushings with the equivalent ///M items.  The ///M
bushings are solid rubber for a firmer, more immediate steering response.
They also offset the control arms' tails outboard, changing the steering
geometry to add a bit more caster for straight line stability, and a bit
more negative camber in turns to improve cornering performance.  I've done
it and I like it.
- --
Bob Sutterfield
'87 E30 325iS http://bmwe30.net #1129
'88 E28 535iS http://m535i.org   #154
BMWCCA #169277 Rocky Mountain Chapter
See you at http://www.bmwofest2002.com

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