Aug 19, 2009· I did a quick look up in a Thompson catalog and looked up their 511 (ball) and 512 (roller) linear bearings, both with 13% preload, both 25 mm rail size. The ball deflects vertically 20 um per 12 kN, laterally 27 um per kN The roller deflects vertically 12 um per 12 kN, laterally 17 um per kN