I bought an 80s frame which I'm building up and wondering if there's a better way than letting the cables keep cutting into the bottom bracket shell.
For comparison, the red bike is my Bridgestone RB-2, which has a plastic guide.
Sheldon Brown recommends a scrap of shifter housing, which he says will stay in place due to the tension.
Elsewhere on the web I saw suggestions to try heat shrink tubing, or something called jagwire housing.
Sheldon also says you can drill and tap a new hole to install a plastic cable guide.
If you drill a hole, how do you keep the screw from hitting a sealed cartridge bearing?
For the scrap of shifter housing trick, does it really stay in place purely from cable tension?

A section of cable inner lining, should do the trick

Thanks for the perspective from both of you.
Repechage, what is cable inner lining? The soft plastic part of the housing if you cut away the metal outside?
SurferRosa, you might be right that some lube in there and maybe it will slide fairly friction free that now there's already a channel worn away after 30 years.

I wonder how long it would take before it would actually cut its way completely through?
It reminds me of a MythBusters episode where they tested whether you could cut through jail cell bars with dental floss. They rigged up a machine that pulled a loop of floss around the bar for a few days. It did cut through a minuscule amount--almost just an etching really. Their estimate of actually cutting through was something insane like a year of 24/7 cutting.

You can search Amazon for example of the housing, it is cheap.

“Jagwire Black Housing Liner 30 Meter Roll, Fits up to 1.8mm Cables” $12.99

I just bought several feet at local bike shop for a few dollars.

What's stopping you from just running a piece of housing over the cable at that location? Doesn't cost you anything to try.

If you don't have any cable liner handy, a cotton swab with hollow plastic stem will do. That's what I use on my bikes after my last bit of cable liner ran out. Snip off the cotton ball ends. The stem is hollow and just the right size for most shifter and brake cables. I use 'em on my bottom brackets and the convoluted metal guide noodles brazed onto the seat cluster on my old Univega with cantilever brakes.

Works great. Reduces cable friction a little too.

I've done this on my bikes....for shift cables that run below as well as above the bottom bracket. I haven't been concerned about the cable wearing on the metal, I'm just trying to preserve the paint / eliminate a potential rust spot. Short pieces of inner cable lining stay in place nicely.

Dean

Shimano Y80098100 is what I use, essentially the same as the Jagwire version mentioned previously. Stays in place fine.

A thick piece of full housing could allow the cable to pop to the side if the lever is downshifted when the chain isn't moving, as the cable housing strands will be working against the curve of the cable.

Granted, the cable popping off one of the grooves is a possibility even with the thin lining - but it's less likely to go wrong, looks neater, and is easier to set with hot glue in a discreet manner.

-Kurt

Smart idea about hot glue! I use it for all the kids' art projects, but didn't think of it for this.
Is the cable liner easy to extract from a scrap piece of housing? Do you tug it out with needlenose pliers? Or use a utility knife to scrape off the outer coating and then peel off the strands of housing body?

neurosurgeons use a diamond coated cable to saw through skull ( well they used to- most use a buzzy saw now ) takes a lot of time.
advantage is the cable saw kerf will be at an angle- staples not required to put it all back together. I know, too much information.
the chances of sawing through the bottom bracket shell by shifting - nada.
Aztec brand cables had a Teflon impregnated cable that slipped well. I use it on a bike with early under the BB cable guides- no room for liner.

+1 for cable liner. Although I do find the cable eventually saws through the liner - takes a while though and is cheap to replace.

I've always left the bare cables on all my bikes. The most wear I experienced was on an Alan aluminum frame. The cable cut into the BB about half the thickness of the cable. That was after 55,000 miles. Then seat lug cracked and that frame went to the great recycler in the sky. Let me add, I shift a lot.

There's a lotta salt hitting this area so I would be careful using something that salty water can creep into. Just make certain when you wash your bike to keep this area nice and clean and waxed.

OP lives is California, no salt used there.
Nothing is really required, but cable lining will ensure a nice, smooth shift. Most bike shops will give you the 6-8 inches needed for this task.

No, not ALL of California is "Malibu Barbie Land".
"SACRAMENTO (CBS13) — As the winter storm continues, so do Caltrans crews who are hard at work treating and clearing snow-covered roads. ... Now they use a sand-salt mixture and pre-treat roads with a mixture of water and salt that prevents freezing."

That is true, some of CA gets a lot of snow! It always amazes me when I read that Mammoth has, say, 10 feet of snow in a really snowy winter. I actually live in the Los Angeles area, so it's pretty snow-free here (although Malibu had a freak storm a couple of months ago and did get a little dusting of snow). I bought the frame from Rccardr which is how he knew that.

There's always snow in CA. Some of it goes on the road and some it goes elsewhere.

OMG I can see your BB is worn!

I think you can tell how much a bike is used by how deep the groves are. Wish there was a depth to years/miles/shift chart!
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They question I'd like answered is there any difference with the insert and what happens when the cable starts cutting through the piece of outer.

[MENTION=535269]lajt[/MENTION] if you're in LA area and don't mind waiting a few days, I have a whole roll of that Jagwire liner, I use it on the kids bikes to cut down on cable rust.

Shoot me a PM with an address, I'll sent you a few feet. I'll literally never get through this roll otherwise.

Wow, I am beginning to understand the plastic under-BB guides secured with a thorough-bolt.

cable liner for the win i also have a roll of it and would put some in an envelope if people needed

Not sure I understand your question. The difference to me is that the liner has a lot more lubricity properties than a steel cable on a steel surface. As the cable starts a groove, the contact surface area increases with a corresponding resistance or drag, coefficient of friction kinda thing. The liner is probably better than when the cable was cutting through the paint!

It is worth checking every once in a great while for the cable cutting through the liner. I don't know what the service life is of either cable liner shown.