[urq] Aluminum subframe bushings...

[Jeffrey Goggin]

> I seem to recall reading a report from Audidudi some years back that Al
> bushings couple more vibration to the unibody of the car and can lead to
> damaging the integrity of the unibody.  Does anyone else remember this
> report?  I know that he was referring to a car that he was auto crossing
...

Yes, I installed aluminum subframe bushings in an '81 4000 with a
four-cylinder engine and Yes, they not only coupled a lot of vibration into
the chassis (remember, the engine mounts to the subframe on the
four-cylinder cars) but eventually caused quite a few spot welds around the
engine compartment to break.  I think the coupling problem (both in terms of
vibration and load) was exacerbated by the fact that my bushings had steel
sleeves for the bolts that locked into the recesses in the engine mounting
rails so as to prevent the subframe from being able to move at all.  The
fact that we had to use a porta-power to get everything lined up so the
subframe could be installed no doubt pre-stressed everything and probably
added somewhat to the breakage problems.  That the car also had 140k on it
was likely a factor as well.

On the other hand, the aluminum bushings really did firm up the handling of
the car as did the aluminum control arm bushings (all of which, I might add,
were cleverly hidden behind slices of the original rubber bushings because I
was competing in a stock class that limited the extent of modifications
allowed) and on the special batch of ultra-soft compound race tires that
Yokohama provided to its contract drivers at the Solo II Nationals in 1989,
the car could pull just over 1g on a 100' diameter skidpad.  No Audi I have
owned or driven since has been able to corner as hard or handle as well as
that car did -- twist-beam rear axle and all! -- but it was definitely a
bear to drive on the street, what with the radical alignment settings and
custom-valved shock damping.  With some more tweaking and tuning, however, I
suspect my '99.5 A4 might be able to better the 4000's 1g cornering
performance and still perform adequately on the street ... vorsprung durch
technik indeed!

(BTW, it's been interesting to observe how the A4's Torsen center diff
behaves as compared to my experiences with the Torsens in the 80/90 and 200
series cars ... suffice it to say, the next modification I purchase for my
A4 will be a Quaife for the rear diff since I can't keep the inside rear
tire planted without otherwise compromising the rear suspension setup and
once it lifts, all drive is lost, which really unsettles the car.  That
said, I've yet to experience any "spider bite" with the A4, but I won't open
that can of worms here...)

Jeffrey Goggin
Chandler, AZ