Any tips on preventing flat spots on modern performance tires when not driving for a few months? My car vibrates at speed after being in the garage over the winter. The tire shop told me that high performance tires are nylon belted and they will take a "set" if in the same position for a period of time which will likley not go away. I cant believe that they are ruined! Can I run them a bit low on PSI to get them hot and hopefully revive them? I was also told that parking over carpet will help to prevent this. Any thoughts on this?

Why not get a set of cheap jackstands? If you are not driving in the winter that should be one of the things you do (empty float bowls, sta-bil in gas, take out water put in antifreeze, etc.)

Good luck with the tires going back to normal I have seen them get better and also not get better, but what do I know

Jack the car up so the tires are off of the ground. Lowering the pressures can be dangerous as the belts can overheat and separate.

I had a friend that swore putting small pieces of carpet under each tire would prevent this, but I can't prove it. I have a truck that does this, it is annoiying.......I have changed all 3 u-joints and the carrier bearing, and it is still there. It goes away over 45 MPH.

I always overinflate my tires when I park my car for the winter, and that seems to prevent flat spotting (though I sometimes drive the car a couple times in spring before I remember the tires are overinflated and let some air out )
Before I started overinflating the tires, I used to notice the flat spotting for a while when I'd first drive the car but eventually it was be OK.

...if the front bushings are rubber and you have the car on jackstands, the hanging A-arms will cause the rubber in the bushings to be deflected or twisted all winter.
..maybe it doesn't matter
..poly or plastic bushings are O.K. as they basically just slide inside their sleeves

i bet if you spin those tires fast enough, you can wear the high spots off....

I have a tire lathe for these kinda problems, but your a little too far away for me to help you.

Last time I saw one of those was in the late eighties early 90s.