JoeTBM 

Our method is to do the rear cables first. After removing the old cable, we inspect the housings for any wear or kinked points. we blow out the housing with compressed air from a blow gun tip, drop a few drops of oil into the housing at the control end and then install the new cables. Sometime the rear cables are good enough to reuse for the front cable replacement, We have a separate parts bin for salvaged housings and short cables from bikes we dismantled.

Yeah I know it is only a few dollars but with 1200 bikes fixed last year at our charity shop, it helps us make best use of donation $.

canklecat

I just did that very thing on a new-to-me used racing frame that a friend gave me. I wasn't sure whether the bike would suit me (I'm too old for racing but was curious to try the bike). It was just the frame, fork and nice Ultegra crankset.

I didn't want to put any money into it until I was sure the frame fit. So I stripped the cables and housings from an early '90s Trek 5900 (currently disassembled for overhaul anyway), along with the handlebar and brake/shifters. Worked fine. I think I had to replace the short loop of cable housing between the chainstay and rear derailleur, but everything else fit perfectly. Surprised me because it's the first frame I've put together with internal cable runs, but the design made it easy -- all the tricky runs, like around the bottom bracket, had cable guides pre-installed.

Anyway, after riding that bike for a week and tweaking it as I went along during test rides, it's a keeper. So I'll devote some new cables and proper housings soon. The old cable housing was bright blue, which was fine with the old bike but weird on the new black and white frame.

I tend to buy cheap no-name cables and housings for stuff like this. Dunno whether cables stretch, but the cheap Sunlite brand brake cable housing definitely compresses. The cheap brake cable housing compresses so much I need to adjust the brakes every ride for about a week. Meanwhile braking feels mushy until it settles in. I'll cough up the money for better cables and housings for this bike.

Ferrules and square cuts on the cable housing ends seem to be a factor too. I took the time to file down the cable housing ends after trimming this time and seemed to have fewer problems with needing to tweak cable tension later. Lots of variables though, like using better components with metal barrel adjusters rather than plastic, etc.

JohnDThompson 

The charity shop where I volunteer is 100% dependent on donations, so we reuse as much as possible. Cables and housings are generally reusable, with a couple caveats. Frayed cable ends need to be trimmed, and cables are often flattened at the pinch bolt to a point where they no longer pass easily though the housing. In many cases, trimming these problem areas still leaves a cable long enough to be reused, and certainly a trimmed rear brake or derailleur cable is more than long enough to serve as a front brake or derailleur cable. Housings typically suffer most at the ends, which become kinked or splayed. Trimming the last centimeter or so off each end and grinding smooth leaves serviceable housing sections. Use of new cables and housings need only be done where salvaged parts are not long enough.

CarryDuctile

Accurate statement above^^^^

klasse

Haven't read all the comments, but: Sautering cable ends is a nice way to preserve them. I generally don't reuse housing.

cxwrench

You must mean soldering. Assuming you're not using a phone when you misspell a word it is underlined in red...that's a clue it's not correct.