Originally posted by fatdoggy
Is the gray foam light weight? Whats the deal?
This is just speculation...
the inner(closer to the rim and lighter in color) layer of foam is probably much stiffer than the outer layer, like a 30/45 shore mix. This would eliminate almost all sidewall flex and any straight-away speed scrub. the very soft outer layer of foam would create lots of grip due to it's softness,with no worries of chunking, lost speed, or hooking that normally comes along with soft tires.
so, the stiff inner foam and the soft outer foam act in concert to make a perfect mix of grip,durability, and consistent performance.
backside?once the outer layer of foam wears more than a few mm, the tires are worthless and won't provide any grip. Probably why they were thrown out at 47mm.