when I was working in the shop and doing overhauls or replacing the cables I might thake the front housings and reuse one for the rear brake and on friction bikes the other for the RD then new housinf up front where it can be seen. I wouls sometimes if they were not bad use the old rear innner cables and the front. yes we always told the customer and only charged for the new ones used.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk