Need help with wheel shimmy

[Slamtry]

I recently put some B14 S-ER wheels with new Falken ziex tires on my
Classic. I am now getting an annoying vibration in the steering wheel at
about 65 MPH. It is exactly the same thing that used to happen on my gf's
Miata at about the same speed. Anyone got any ideas what I might do to fix
this?

Is this likely to be a wheel/tire/balamncing issue or is it possible that
alignment (which I plan on getting done, but have not done yet) will fix
it?

BTW, the tires were installed with the yellow dot next to the valve stem
as per Falken's website.

TIA

Dan Hugh-Jones