so i've got 16x8 rims from a 93 300zx non turbo. i ran the tires that came with the rims for a while but there wasn't much tread and there was a vibration at 75 mph. when i got new skins, the wobble persisted. i got the tires rebalanced, and the wobble improved, but is definitely still there. in winter, the snow tires on my OEM rims run smoooooth.
so...
do i need to try another wheel balance? a different type of balance?
are my rims bent and all the balancing in the world won't do a dam bit of good?
am i screwed because the 300zx is a rear wheel drive car?
any opinions would help (except telling me that i was an idiot for buying used rims from a salvage yard)

 

Have you looked at your brake rotors lately?

 

the rim might be bent. If the wobble is only at certain speeds, probably bent. if the rotor is warped it should only vibrate under heavy-moderate braking.

 

sounds like a bent rim(s). LIft the car and see it for yourself, or have your frined drive the car and follow from 7 o'clock and 5 o'clock to look at both sides.