An old topic I know, but after several years several of my wheeled vehicles that came with rubber tyres are degrading & splitting.
Most were primed with acrylic grey primer from a rattle can and painted with either enamels or acrylics.

So what is the best primer, am just about to start on several Trumpeter Stryker kits?

Neil

I simply don't paint them, just apply some pigments for weathering, it's enuough IMHO (except if you want white stripes...)

Same here I don't prime them. A quick sanding of the tread and some pigments usually does the trick. Sometimes a bit of rubber colored acrylic paint on the treads to finish.

Unless you have the dragon DS tires , sorry I just had to sneak that in .