The formula requires mass? Did I say anything had no mass? I'm sure this was taken into account. According to them, these pulleys are proven and tested to absorb torsional vibrations earlier than OEM and further into the RPM range. They said they can customize the "spring rate constant" which in this case is not an elastomer like OEM but dry friction. If it is determined that it needs different range of coverage that is. The tuning is not hard at all, you just have to specify what you want.