RE: Subframe bushings...

[Mike Zamikhovsky <MikeZ755@sprintmail.com>]

-----Original Message-----
From:	JustaxPHX@aol.com [SMTP:JustaxPHX@aol.com]
Sent:	Friday, February 05, 1999 7:02 PM
To:	quattro@coimbra.ans.net
Subject:	Subframe bushings...

>That lister was me ;)  I'm not sure how much adjustment ther is by moving the
>subframe, but you should have good bushings, or else all your hard work would
>be for nothing.   If they pull the subframe forward, it will add a little
more caster.

Actually, "bad" bushings can be good if you're willing to let ride comfort
take second place to performance.  When I was autocrossing an '81 4k, the OEM
bushings were so far gone that the metal inner sleeves had separated from the
rubber, which allowed the subframe to move up and down on its bolts quite
freely.  However, by using fender washers that would fit over the sleeve, it
was possible to shim the gap between the bottom of the OEM washer and the top
of the bushings and jam it tightly against the engine mounting rails and
thereby keep it from moving around as much under load.  It also had the effect
of slightly raising the inner pivot points for the control arm, which improved
the suspension's camber-gain characteristics.  If you were careful about it,
it looked almost like it was stock ... certainly no one ever figured out that
it wasn't factory stock while I was competing in a stock class!

Also, if you want to experiment with changing the amount of anti-dive in the
front suspension (or anti-squat that's in the rear suspension of a 4kq), you
can put some of the washers between the subframe and engine mounting rails ...
if you over-do it, though, the car will become quite darty under braking,
especially on bumpy surfaces.  It'll also stiffen up the ride quality
somewhat, both of which may not be a plus for regular street use...

>BDTD.  It seems that either the subframe moves around from time to time.  It
>is often ignored when an alignment is done.

The subframe definitely moves around under load ... the problem, though, is
that if you restrain it, you simply transfer the load into the chassis and
after a while, cracks start appearing in the sheetmetal all over the engine
compartment.  I did a set of custom aluminum subframe bushings with steel
sleeves that locked into the recesses for the captured nuts for the subframe
mounting bolts and while it made for a significant improvement, performance-
wise, it literally trashed the car in less than a year.

I still have the bushings and have been tempted to install them on my Ur-Q
except that so far as I can tell -- take it easy, Dave -- the structure is
pretty much the same.  Given the increased loads caused by the wider wheels
and a heavier car, I'm therefore somewhat concerned that they'll cause the
same damage over all again, except more quickly...

JG



This is the very thing that I mentioned many times before. When solid bushings and strut braices are used the shell gets trashed. In order to slow this process down one needs seem welding and roll cage that ties together subframe and other suspention pick up points. I am currently in process of converting my rally car to all solid Rose bearing suspention leaving only one rubber component per corner. It is beyond most people's understanding how much work is needed to prepair the shell to survive something like that. One big problem that I found with Audi is that subframe attachment points are relatively week. I have seen toren out subframes more than I thought I would both in rally and in street use.
Mike Z