any trade offs between 16X7 and 17X7 rims

[cthulu703]

17's have more brake and strut clearance. 17's are really the only way to run a 235+ width tire on an E30.

There are tons, and I mean tons of light 4 lug rims out there, you just have to use spacers and studs. I am running 16x7" Honda rims that are 14lbs a piece, were cheap as hell, and are very strong.

You never have balance problems? No vibration? If so, what kind of spacers do you buy (ie manufacturer)?

[Digitalwave]

You never have balance problems? No vibration? If so, what kind of spacers do you buy?

Vibration with spacers is an internet myth. The key is to make sure everything is hubcentric. I have hubcentric (57.1mm) H&R TRAK+ spacers, and hubcentering rings on my rims since they have a 67mm centerbore.