First post here, so please help me out if I'm leaving out essential information or violating some local standard.

EDIT to add: This question is really meant to be specific to vintage Schwinn's, if they used standard outer cables, I would just do that.

I'm fixing up (really just getting back into service) a Schwinn tandem from 1968. I want to replace the shifter cable, but wonder whether it is usually better to replace or reuse the outer cables? From what I have found browsing, they are not standard, and so harder to find the proper replacements. The ones on the bike look like they are in decent condition, just dirty.

What do you all do, and what is the standard for deciding to replace?

I am thrifty when it comes to my own stuff. I know most here will say if you are asking then it should get replaced. If you can do the following the steps below, you can save a few $. Or delay the purchase so that you will be buying more bike related stuff at the same time. Otherwise look for a tandem shift cable. Most decent bike shops and online bike suppliers have them.

1. Cut the end of the cable so that it is not frayed. This may not be possible. It's not you, the cable might be too worn.
2. Be sure that after the cut, you will have enough cable to get back in the derailleur clamp.
3. Remove the cable from the housing
4. Inspect the cable to be sure there are no kinks or rust spots and it passes
5. Inspect the cable housing to be sure the plastic cover is intact and that all the spiral of the steel part of the cable are intact. It is wound like a spring. If there is a kink anywhere, the housing is no good.
6. Grease the cable. It is a messy job especially with a tandem cable. The cable will will end up all over the floor and/or the workbench and will collect any dust that is on the floor or junk on your workbench. You could get a willing assistant or two to hold the ends. You need to get the cable nice and greasy. Most assistants don't what to get involved once they know what you are up to (just my experience).
7. Feed the greasy cable back through the shifters, the cable housing and into the derailleur(s)
8. Feed the cable into the cable clamp on the derailleurs.
9. You'll have to do this anyway, but you will have to adjust the derailleurs. There are some online videos or check back with us if you need help.

This is really a matter of is it worth it to spend the money and get the part that will go in and be trouble free or to spend the time, effort, get messy, use language that you regret and the chance that it won't work in the end.

For me, that is all worth it. For most of the rest of the population, it is better to spend the money and get the right thing and not have to worry about it again.

For instance, if it ends up shifting poorly, you will be asking yourself and perhaps us, "is it the cable or is the derailleur sticky?".

There is always the chance that you try it, it doesn't work, but now you know how to do when the new cable comes in.

The most important thing really is getting to ride your bike again.

There isn't an absolute need to replace the housings. It is generally a good idea to replace them anyway. Modern lined housing will reduce the cable friction somewhat. Also the plastic covering may be starting to degrade by now.

If you reuse the old housing, they should be pulled out and cleaned. Any damaged ends should be clipped off, and all the ends should be ground or filed flat again. Don't forget to put back any ferrules. Grease the new cables generously, and reinstall.

Is it a single piece of housing going all the way back, or are there stretches of straight "open" cable between stops? If it's the former, given the extra length of the cable, a new housing would probably be a good idea. As mentioned above, modern housing will provide lower friction and smoother operation.

You will find that modern housing may not fit into the cable stops on older Schwinn bicycles. You may need to save it. It usually cleans well. Use new cables, and lube them well if reusing the old housing.

This exactly. I haven't removed the housing yet, but from everything I understand, modern housing won't work. I can find some on ebay that claims to be a correct replacement, but I would be buying enough to do about 20 bikes. I guess I was hoping for some sort of experience based indication of "x, y, and z conditions are fine, reuse; a, b, or c condition means suck it up, buy the long roll of housing and plan to store it properly for a long time."

I'll probably try to reuse, unless someone chimes in with the "suck it up" conditions to check for. Thanks also to Velo Mule for detailed description of lubing it up. I would probably just have used a dry chain lube with is what my LBS has always advised for brake and shifter cables.

I use 90w gear lube on the inner cables of old Schwinn's, maybe because I have it and it's cheap.

That is not correct. Modern housing will work fine. Main issue is that it might look stupid. Also, modern shift housing must use ferrules (end caps), and there is a slight possibility you may have some trouble fitting it into whatever cable stops are on your bike.

FWIW there didn't used to be separate brake and shifter housing, as shocking as that may be. It was the same. Really any coiled housing will work.

Modern shift housing was introduced in the mid 80s, and is made with linear strands of wire that are parallel to the cable, so that it compresses less.

Dry lube is not correct for vintage unlined cable housings for brakes or shifters. They should be greased. Very heavy oil is ok if that's your preference.

It is the diameter of the housing that is the issue. Old Schwinn housing was smaller than modern housing.

The advice I got at my bike shop was that it was fine to try to reuse it. As for cleaning up well, or for looking stupid, the only place there is any is right over the bottom bracket and then a few inches to the derailleur. I don’t think it will be very visible either way. Thanks for the help, hopefully this bike will be rolling again soon.

Updating this thread. I just pulled apart my 1972 Schwinn Sports Tourer and found that modern brake cable housing is a little too large in diameter to fit into the stops brazed onto the frame. The difference is small. I bet I can sand off some of the outer plastic on the housing to get it to fit.

Modern shifter cable housing fits just fine though into the brazed on cable stops. Jagwire sells a shift cable that will work with the Huret shifters,

https://www.modernbike.com/product-2...RoCMaMQAvD_BwE