[A4] how spare is the spare?

[F550V12 at aol.com]

When I bought my 2000 2.8Q with 55K miles, I had two tires worn and two tires 
with good tread.  I replaced the two worn with the same tire (Continental) 
and had them rotated, and my ride is a little shaky, but I've yet to take my car 
in to find out if the shake is caused by tire imbalance or faulty control 
arms/tie rods. (Nor will I until it's TOO shaky or if I do it as a causality of 
my 64K mile tuneup.)