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RE: Track control arms

> Tim Holmgren writes...
>
>     In the August issue of BMW Car there is an M6 featured which has been
> highly modified and refined, to say the least. One modification involved
> fitting "competition pattern track-control arms" to quicken the steering.

Tim,                                                        
	I've not seen that issue, but I'd like to point out a few things.
First of all, without modifying the mount point of the control arm to the 
body, there is no way to change the steering geometry, per se.

	To quicken steering, the most effective way is to reduce flex in 
the suspension geometry and chassis mount points. Of course, a stress bar 
quickens steering, but so does replacing rubber bushings in the 
suspension that flex under load (thereby softening the suspension and 
slowing steering down by absorbing the delta). Probably the greatest 
improvement can be seen in the thrust rod bushing, followed by the lower 
control arm bushing and upper strut mount. If you choose a harder 
durometer rubber, delrin bushing, or most radical a  rod end (aka Heim 
joint or monoball), ride quality degregates.

	Going to 750iL (or Dinan) thrust rod bushings can increase the 
stiffness of the thrust rod. Alternatively, one can modify both the 
thrust rod and control arm such that the bushing end becomes a rod end. 
This is fairly common practise for road race cars, and can be performed 
by a competent race fabrication shop.

	IMHO, a good set of 750iL bushings and front stress bar, combined 
with a proper working suspension (shocks and springs are in good 
condition) will provide one ample quick steering in the M6...

Filippo Morelli
E28 M5 (regretably for sale, but with 750iL bushings and stress bar).