The second one, even more important, is that urethane gives a really good grip with the ground. It will slide if you push it hard, but it gives great traction. So that means you can control your board. He also points out that with wheels, adding cool colors may actually weaken the wheel. Urethane is normally a whitish clear color, when it's poured with no other agents.
Less urethane means less resiliency in the wheel.
Dyes are arguably better than pigments, which really take up a lot of space. But some people argue that dyes alter the chemical structure of the urethane itself. When people are really looking for a high-performance wheel, we recommend a clear wheel. So, as the wheel turns, the section of the wheel that is in contact with the ground is flattened a little bit by the weight of the skater pressing down. Engineers refer to this flattening as deformation.