  Contactless bearings based on both permanent magnets and superconducting
magnetic levitation are interesting to avoid all the tribological problems
associated with contact at very low temperature. Superconducting magnetic
bearings (SMBs) find application in mechanical engineering where lack of
contact is a requirement or an advantage. In comparison with active magnetic
bearings (AMBs), SMBs solve their inherent instability and require less complex
control strategies and electronics. However, one of the current limitations is
their low mechanical stiffness. Force densities are considerably lower in SMB
than the state-of-art values for AMB. This fact certainly limits their
applications. In this chapter, we summarize some key strategies for the
improvement of radial and axial stiffness among with a description of some SMB
in terms of load capability or force relaxation and discuss their advantages
and disadvantages.A set of rules for the mechanical design of high-stiffness
thrust superconducting magnetic bearings are proposed and experimentally
demonstrated. Keywords Low-temperature tribology
