Front end vibration

After I had my new tires installed I notice that the steering wheel shimmies from 40-50 MPH. Before that and after that it is fine.

I had no problem at all before the tires. I don't know alot about front ends so is this more likely

A: Tires balanced incorrectly? or

B: Need for an alignment?

Any informed opinions will be greatly appreciated so I can take it to the right place to get it fixed.

Thanks

tires need to be balanced... steering wheel shaking has nothing to do with alignment... depending on wheels/tires, may be a PITA to balance, but it can be done... yours just weren't done correctly...

Just balance & align them - vibration should go away.

Definately a balance issue. At 40-50 your hitting a critical rpm for the amount of unbalance in relation to the unsprung mass of your tire. A proper balance job should alleviate the problem.

Thanks guys, I'll take it back in for a re-balance tomorrow.