New tires - still vibrate (Coupe GT/SP 8000)

[Kwattro@aol.com]

Well, I plunked down my 404$ and got a set of Z rated 195-55-14 Dunlop 
SP8000's
for the GT today.  And man, they're great cornering tires - I haven't pushed 
too hard (don't want to kill'em early...) but they felt very stable, with 
lots of grip, and the highway ride is no worse than before.  Turn in is 
better.  Downside:  The car still has a distinct vibration between 50 and 65 
mph.  Before I take it back to Sears, is there anything else that it could 
possibly be?  I suppose it could be a driveshaft or something of that sort, 
but I had the car completely checked for the Limerock BMW event no less than 
30 days ago, and I didn't drive it for 10 of those days.  Hmm...

Looks like back to Sears for me.
BTW, anyone responding with bad tire casings due to improper castings - i 
haven't ruled that out, but the reason I bought the SP8000's over the RE-71's 
was that they were supposed to be better casts, and the RE's are never really 
properly balanced to begin with.
Any help?  Thanks!
Carter J
Kwattro@aol.com