Originally Posted by
JohnDThompson
I remember when Dura-Ace SIS came out, one of the big concerns riders had was the loud "click" whenever you changed gears would alert other riders to what you were doing. That's why SIS came with an option to go into plain friction mode with a turn of the D-loop.
That's an urban myth created by the detractors of SIS. Detractors even claimed the presence of a friction mode was proof that Shimano did not have complete confidence in the reliability of SIS. In reality, the friction mode was a back-up system in the event the SIS could not be used, such as a crash that put the hanger slightly out of alignment or a flat which forced the use of a neutral support wheel with a non-SIS freewheel. The latter was a huge concern, given the intended racer market and the non-standardized spacing of freewheel manufacturers.