Steering wheel vibration?
 

ok, so I just got new wheels/tires yesterday!! !5 x 6.5 Rota Grids wrapped with Falken Ziex 512 rubbers (195/50/r15). Everything is fine and all but when I get up to 80ish my steering wheel starts to vibrate. Howcome? The wheel's were mounted and balanced prior of course....so why is it vibrating? do I need hubcentric rings? or was it just not balanced right? or is it just (although HIGHLY unlikely) an aftermarket wheel/tire thing?

Could be you need rings. Could be that the tires balance OK at the speed the balancer spins them but as they go faster they change shape slightly and thus go slightly out of balance. I might ask the dealer how fast the balancer does spin. Although those are not cheapo tires. They should be hold shape at 80ish. Could be a tire that is little out of round or a rim that is not perfeclty true. I have had all these things happen at one time or another in 30 some years of driving. The fact that it happens at high speed only makes me think they should use a balancer that will spin the tire on the car. I haven't seen those in a while but as I recall it spins them about 100 mph.

Unless your new wheels have the proper size hub center you definitely need the rings. Using just the wheel studs doesn't center the wheel to the hub. Cheap insurance IMO.

Hub centric rings for custom wheels is a must. and also if the boys in the shop aren't that good it could be they aren't balanced properly, I had both problems ! They forgot the xB needed rings had to send them later, and then they tires still shook the car, then i went to my local shop and had them checked, found 2 tires so far out of round that they had to be replaced, the company paid for the work and sent me two new tires, then i had to go back again and balance those two also. but after all that ........the tires are fine.

Find a shop with a descent machine, bubble balance isn't the proper way to set custom wheels up anymore, find one that can detect wheel roundness and tire roundness and compensate for that. Sometimes they can rotate the tire on the wheel to fix it too. Good luck !!

Very good suggestions I forgot about that. Also make sure the balanced them with the weights on the outer and inner (more towards the center of the wheel. On my first set of tires they only had weights on the back side of the wheel and they were never "right" from the get go.

how do I know that a shop has a good machine?

It will have a video screen and an arm that gets moved to the place that the weight has to be placed on the inside of the wheel.