watch the video first, it has been over-dubbed from Russian to English.
The idea of putting Concrete in the tyres came from up-sizing a previous vid where they tried Foam, if I can find it, I will post that.
He admits he is no construction worker, so mix may have been wrong, but is it worth trying on a longer rest between mix and cure.
Couple of ideas to work with, he was using a Lada Rive, I have had one, they are strong, rigid, underpowered, will eventually break a speed restriction of 70mph if you give them a long enough run at it, but quite happily plod along for many years.
But.
The wheels are not special.
As you can see a LOT of tyre.
What if they used a lower profile tyre size on bigger wheel to reduce unsprung weight?
The brakes on a Lada are "Utilitarian" dual circuit but nothing special.
Could they get that aerated concrete to work, the kind of stuff used for construction on inside walls?. Its lighter.
But would all the air create a weak structure?