Tires: Tire pressure and balance, inflation pressure, tire pressure

Question
I have an Austin Healey Replica, I had new tires installed at Firestone. When I
drove the car home, I had a noticable shake in the front end. When I got
home, I checked the tire pressure and found it at 30 psi. I had asked them to
set the pressure at 22-24 psi (recommended by manufacturer). I reset the tire
pressure to 23 psi and most of the shake went away but there is still some
shake at 55-65 mph. I also checked the lug centric mounting of the wheels
and the proper lug torque. I was wondering if the tires would be be in balance
if the pressure was reduce by 6 psi. It still feels like a balance issue. I didn't
have this problem with the old tires.
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The text above is a follow-up to ...

-----Question-----
Is a tire which is balanced at 30 psi still in balance when pressure is reduced
to
22-24 psi?
-----Answer-----
Jim,

Changing the inflation pressure does not affect the balance.  However,
changing the pressure might affect a tire that is out of round.

But I would appreciate knowing why you asked the question, as this is rather
specific and unusual.

Answer
Jim,

You probably have a problem with the tires being out of round, but the lug centric rims are a problem, too!

Of all the things to do, getting holes bored straight, perpendicular and in a circle is one of the more difficult.  This means that it is difficult to have the rim to be centered properly.  This also could be the source of the vibration.

Try taking off the rims and remounting the carefully, being sure to avoid tightening any one lug too much before the others are.