My question is about brake cable sizing standards. It seems like 5mm is the standard, but I know that 6mm cables were used in the past. The problem is that 5 mm doesn't seem to work on my frames, without shimming.
I am replacing the brake cable housing on two older bikes, and have a problem with fit in the cable guides. The bikes are a 1983 Trek and a 1989 Paramount. Both have braze-on cable guides on the top tube. Both bikes came to me with non-original housings - and both were 5 mm, but they fit very loose in the guides, so they allow the housing to move too much. I use sidepull brakes, so the housings need to be snug at the rear guide near the seat. I have some 30-year old 6mm housing which fits pretty good and snug in the Trek, but will not even fit into the Paramount guides. I don't have enough of this old housing to do either bike.
Outside of using some ulgy means to hold the housing in place, I am looking for suggestions.
Here are some photos - the Trek is the yellow frame.