I am in the midst of rebuilding an early 90s Diamond Back Master TG road bike. I have come to rebuilding the rear derailleur system. The bike is equipped with downtube shifters and the cable only had housing in a loop from the chainstay cable stop to the rear derailleur. This is the only bit I need. The rear shifter is selectable between indexed and friction. Frankly, is derailleur-specific housing absolutely necessary in this application or would brake housing suffice?
I question the importance of derailleur housing in this application due to the slight movement of the derailleur and after reading somewhere about how the helical strands of derailleur housing really only come into play as reducing housing compression when in frequent-movement application, i.e., from a bar-end shifter to a downtube cable stop.
Thanks in advance!