High speed vibration
 

Took my car for an aggressive drive today and noticed an interesting vibration that starts at about 100 mph. I can feel a vibration that seems to travel from from front to back to front, etc. I feel it in the steering wheel and it gradually subsides as I start to feel it in the seat. After a few seconds it fades away and recurs in the steering wheel again, and so forth.

Below 100 mph all is smooth. Here's some background:

New B-stone RE-730's on straight, true Fuchs (7 and 9 x 16)
Recently aligned and corner balanced.
New Koni Sports all around.
New 22 and 29mm torsion bars.
Neatrix bushings.
Rack spacers.

It's not a severe vibration but noticeable. All suspension work was professionally done within the last 6 months.

Any ideas?

If it appeared with the new shoes...I vote for having them matched balanced. Could be there is a slight high spot on one tire that could be moved to a low spot on the wheel.

Evey vibration I have encountered that comes and goes with speed, has been fixed with rebalancing the wheels/ tires. Usaually it first starts with a shaking steering wheel then to the body and then subsides. You might have lost a balance weight at those speeds- It is probably the cheapest place to start- Hope that helps, keep rockin' brother!

I agree that you probably have one tire that is less than perfectly round. I've seen it on even the best tires. Sometimes you just have to send it back and get another one.

As avi8torny pointed out, you can sometimes reindex them on the wheel and take care of it.
But unfortunately that won't work on the notoriously perfect Fuch's wheels, which just don't usually have any out-of-roundness.

Have your tire guy look very closely at the tires as they rotate on the balancer. If any of them are (significantly) out of round, send them back.