When Running no mag cars tire choice is a big deal when trying to find traction. Recently I have found a great source of rims and inserts that cater to the static modellers. The rubber that comes with them is decent, but the cars still need more grip, Unable to find any tires made commercially I ordered up the supplies i needed and cast some tires. The results have been good. 1/43 scale tires take very little product. The smallest urethane set I could buy has enough material to do hundreds of tires.
They are almost too grippy, and I have started blending some inert material in with the rubber to lessen their adhesion to the track. Base material has a shore hardness of 30, so my suggestion would be to start with 40 if anyone else is thinking of this.
Cheers
Dan