[alfa] Poly bushings

["Bain, Bill" <Bill.Bain@xxxxxxxxxxxx>]

Andy Kress (who's on the list) sells Performtek and is quite
knowledgeable on this subject, but here's my $0.02 as well:

Poly is more resistant to environmental degradation (particlarly
exposure to ozone, grease and oil) than "rubber", which is likely
neoprene, and thus is likely to be more "durable" in that it won't
become softer with age.  It CAN be made "harder", but it is not
necessarily the case since all sorts of properties can be designed in.
Since most drivers have at least the perception that "harder is better",
it's likely that after market bushings are harder, but IIRC that Andy
indicated that the change is on the order of 15% or so, which is not the
orders of magnitude that some folks suggest.  In the driver's side
forward trailing arm bushing, I'd try  poly since that particular
bushing sees a lot of deformation from engine torque and can wear out
prematurely.  The rear differential bushing is a toss-up, some
suspension tuners like poly, some "rubber."  I don't recall that rear
sway bar end link bushings are available in poly so rubber is the only
option. Rear sway bar to body bushings are available in poly, but note
that the last set of ones that I bought for the OEM bar from Alfa were
poly as well.  In the front suspension there are only a couple of
bushings that can be replaced -- the front caster bushings can be poly,
but I think the rest are only available in OEM, which is usually
"rubber."

If you're doing a bushing R&R as a part of a  spring replacement, you
should talk with the maker of the springs before you do anything.  I'd
use what they recommend (Alan Ward prefers rubber, for example, or at
least he did when I was putting my car together).

One other point in talking to the "tuners."  Racing practice is not
street practice.  In racing, the part only has to last for the length of
the race, plus enough to get the car back to the pits.  In that sense
the "best performance" vs. "street car" dilemma is drawn into sharpest
focus since most street car owners would likely not tolerate inspecting
and possibly rebuilding the suspension before each "ride", so the
longevity of the part in normal use is a key consideration.  There, I
believe, poly has a significant advantage.

Bill Bain 
AROC Atlanta 
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