[s-cars] Rear suspension epiphany (Fritz und Hans invade engineering dept?)

[Tony Guttmann]

Some weeks ago I wrote asking about bushes for the rear suspension cross-member.
Dave Forgie put me in touch with Addict Motorsport Design, who sell these in
aluminium for $75 a set. The originals are not purchasable--one needs to buy
the entire cross member for (in Australia) US$2250. When the suspension people
removed the cross member, they had to burn out the original rubber bushes, but 
the steel core, through which the mounting bolts pass, was found to be 16.5mm in 
diamter. The new bushes, and the factory bolts, are 10.5 mm in diameter, and so 
the new bushes, made by AMD, fit perfectly.  

The suspension shop said that when they fitted the new bushes, everything lined up
perfectly, compared to the slightly out of alignment bits before, and my rear suspension
noise has disappeared, and the old bushes on other suspension components that
appeared to be under strain are now perfectly aligned.

I pass this on for the possible interest of the list, no affiliation with AMD, just
a happy customer. But the mystery remains--why did Audi supply bushes with a 16.5mm
hole and then pass a 10 mm bolt through them? Did they want the rear subframe to wander
and twist around or what? And before you speculate--it's not that they started life as
10mm and wore. The holes are perfectly round, and all four are the same diameter.

Tony Guttmann
'94 S4 with 97,000km