The radius (r) of the curved cable routed from the bike frame to the RD-R9100 becomes smaller than the radius generated with other rear derailleurs, as shown in the images below. The commonly used outer casing, OT-SP41, is too rigid for such a small radius that it could cause technical problems on the adjusting barrel and disrupt the smooth and rapid engagement and disengagement of the rear wheel from the frame. By using the OT-RS900, such problems can be avoided as the stiffness is reduced on the OT-RS900.
**OT-RS900 must only be used on the rear derailleur side. It must not be used on the shifter/brake side.