Patent ID: 6881353

Claim:
A magnetorheological fluid comprising: 10 to 14 weight percent of a hydrocarbon-based liquid; 86 to 90 weight percent of bimodal magnetizable particles; 0.05 to 0.5 weight percent fumed silica; and 0.5 to 5 weight percent, of the liquid mass, of an additive package including a stearate and a thiophosphate, and wherein the bimodal magnetizable particles consist essentially of: a first group of particles having a first range of diameter sizes with a first mean diameter having a standard deviation no greater than about two-thirds of the value of said mean diameter and a second group of particles with a second range of diameter sizes and a second mean diameter having a standard deviation no greater than about two-thirds of said second mean diameter, such that the major portion of all particle sizes fall within the range of one to 100 microns and the weight ratio of said first group to said second group is in the range of 0.1 to 0.9, and the ratio of said first mean diameter to said second mean diameter is five to ten.