As discussed in earlier chapters, MR dampers and mounts are most actively and vibrantly researched in automotive engineering. Vehicle brake systems comprise another possible application of MR ™uids. A brake is a mechanical device that inhibits motion. Brakes are generally applied to rotating wheels (or axles) to stop a vehicle. Most common brakes use friction to convert kinetic energy into heat, although several other methods of energy conversion may be employed. There are currently some efforts underway to develop a variable resistance brake utilizing MR ™uids. Webb developed an exercise apparatus using an MR brake [1]. Avraam et al. proposed an MR brake for a wrist rehabilitation application [2]. Development devices associated with an MR brake to replace conventional systems, which usually possess a complex actuating mechanism, also recently received great consideration in the „eld of haptics [3-5]. Several applications in the automotive industry using MR brakes have also been proposed [4, 6].