Fluctuating tires / steering...?

Ay municipality,

I'm not actually a first-post-then-best person, but you could oil a little balm on my soul:

On my 4.2 of 1993 there are stone-old and pretty porous tires on it, which are now also completely down at the front of the outer edges (this under 3 bar disease, annoying!). Big inspection is now on, then probably also new tires have to come, Omi has already looted the savings stocking and given green light (hallo David, I had to think of you...).

My concern: For two months the steering has fluttered slightly at 50 / 80 / 110 km/h, you can also feel a very easy knocking or beating during the ride. I think it's probably due to the old tires, but to be sure, I had the front wheels rebalance again last week (sometimes a weight flies away or something).
I should have gone to dinner for 15 euros, no difference. The mechanic said they could get a high blow, too. It doesn't matter, it's new, but can it be anything else?
I got the brakes from the RS2, but it brakes perfectly evenly and without irons. And the straight run is also right.

I just wanted to hear about you guys' experiences before I spend 1000 marks on tires and axles next week and then have to put it all down again, because the steering is still fluttering.
Remote diagnosis sucks, I know. But any ideas...?

Greetings from the fog-kiel

Sandman

P.S.: I sell my old computer on weekends, I can only be here once in a while for two weeks or so.