I posted this in the tandem forum........maybe this is the better palce for this question.
I recently purchased a 1989 Duo-Sport and have yet to begin to tear it down for overhaul. This is a first tandem for me but I have many vinatge road and MTB bikes so bike mechanics is not new to me. On this bike, there are no cable guides under the bottom brackets but three small metal brazed on loops that the bare cables pass through. The loops seem too small for cable housing and there are no stops for cable housing. Bare cable passing over the bottom brackets can't be the way it is supposed to be is it?

Timm40, Just a guess, but if down tube shifter were used originally, then there would be no housing stops. Two of the loops are possibly for the derailleur cables and the third for an aux. brake.

Brad

Sure, that's normal except most road bikes have a grooved plastic plate under the bottom bracket shell to guide the bare shift cables. If you can't fit one of these guides, you could put a short section of housing liner over the bare wire where it goes through the loops. I do wonder why 3 loops and what the third one is for. Possibly a drum brake?

Edit: Brad you type faster than I do. Even if bar end shifters were used, there would be bare wire under the bb shell.

This does have Bar-Con shifters.........normal stops on the down tube bosses.......all of my other bikes have nylon or plastic cable guides that the cables pass over under the bottom brakets.......and then they go aft to their repsected places. On this bike, neither the eccentric BB or Stoker BB have any sort of cable guide for bare cable........just these three small brazed on loops that each cable runs through.........even looking at the FD cable should have a little more clearance than being jammed in the chainstay/seat tube joint as it travles up to the FD.

.........If you can't fit one of these guides, you could put a short section of housing liner over the bare wire where it goes through the loops..........
I wonder if thats how those small loops are supposed to be used?
There are no threaded or non-threaded holes in either bottom bracket.

Quite the opposite, lots of bikes (if not most of them) do it exactly that way. My Specialized TriCross, for one example, has a plastic tray under the bottom bracket with guides for bare derailleur cables.

Yes I know.........all of my other bikes have this also.....it's all I've ever known. But these bottom brackets have no hole for either a tapped cable guide or just push in type. I have never seen brazed on loops under a bottom bracket. How is Schwinn these days at answering tech questions on out of production bikes?

You have to have some sense of history here.

Early iterations of FD cable routing used a housing loop to an arm on the FD, similar to how RDs still are today. The Rd cable was routed through a section of housing over the BB, or a through a small clipped-on noodle.

Later the housing loop and noodle was replaced with an open clip mounted at base of the downtube passing the wires over the BB.

At some point a few of us started looping the FD cable under the BB shell, and up between the chain stays. Some also ran RD cables this way, but some couldn't because the rear loop stop was brazed above the chainstay.

Later a few builders inverted the chainstay stop, so both wires could be routed under the BB. With more people routing this way, some started refining the concept with guide loops like the OPs tandem. Also as the trend started moving beyond the fringe, people started worrying about the paint, so either better noodles, or curved C-channel guides were brazed on, while those without real provisions would simply trap a piece of housing or tubing down there.

When it moved to the mainstream, owners were more finicky and wouldn't accept the cruder methods of the past, plus builders got tired of the extra work involved in cutting, curving and brazing noodles, so eventually the clip was introduced, making for a finished look, with less work fro the builder.

The reality is that the guide isn't necessary, as demonstrated by all those who routed below the BB before the guides existed.

I found a thread about old Colnagos doing the same thing.......some people just made sure it stayed clean and kept a smal dab of grease there....others found something to place between the cable and BB. I have some old plastic drawer slide material with an adhesive back that would work nicely. I finally got a good look under there and it seems by wear marks that it has always been this way. Thanks for everyones input, ideas and suggestions.

Don't forget running bare cables over the bottom bracket:

I didn't forget, but skipped it as another evolution of the 626a open clip.