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I have an "old" bicycle. The branding on the frame suggests it's a "Coppi", and I believe it to be from the 80s.

There's a lot that I don't know about the bike, but for the purposes of keeping this question succinct, I would like to know about the bottom bracket shell.

One of the things I found interesting about the bike was that it seems to have access ports for internally routed derailleur cables. Personally, I would like to route the cable externally for easier servicing.

I want to buy one of those cable guides you can find on the bottom of the bottom bracket shells. All my other bikes have this cable guide attached by some sort of bolt, but there isn't a clear place for a bolt to go.

here's a picture of the bottom bracket. It has an oddly shaped cutout

If I want to convert the internal cable routing to external, what kind of cable guide should I buy?

Really out of my depth here, I'd love for any pointers you may have!

Edit: I will include more pictures about why I think this has internal routing. Sorry the bike is so dirty 😅

photo of the downtube with the supposed entry port circled.

There is something that looks like a small entry port on the downtube near the downtube shifters (both front and rear). It doesn't feel like someone simply took a drill to it (kinda looks like it though) because the area is slightly raised in comparison to the otherwise uniform downtube.

the supposed exit port for the internally routed rear derailleur cable is circled in red

There is a hole that also looks kind of sus, but is conveniently right by the part where you'd use some cable housing before the derailleur.

the supposed exit port for the front derailleur is circled in red

Right by where the front derailleur would be is something that looks like an exit port.

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    Please photo the other cable points (rear stay, down tube etc) so we can see what you're working with. I have some ideas.
    – Noise
    Commented May 26 at 16:20
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    @Noise I have included some extra photos! Commented May 27 at 2:13
  • Thanks. What happens when you poke a new gear cable down the hole? They may be complete runs and just pop out where they should. Then there is no advantage to changing to external. Use a new gear cable so no snags.
    – Noise
    Commented May 27 at 21:08

3 Answers 3

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UPDATE your third and fourth photo definitely look like internal cable routing. The silver chainstay hole lines up with the braze-on stop, and even the downtube shown in the second photo would be in exactly the right place if you had downtube shifters.

The rest of this answer is less relevant now.


While its not impossible the holes are for cable routing, I'd guess its either just a fancy cutout for weight savings/drainage, or perhaps there's a cover plate supposed to go there which is missing.

Bikes of that era didn't always have braze-on cable stops. Instead, they could have band-on stops like this:

https://www.retrobikefranken.de/images/product_images/original_images/Sachs-Doppel-Gegenhalter-beidseitig-Unterrohr-Zugf%C3%BChrung-Anschlag-Schelle-Rennrad-2-.JPG

And a bottom bracket turn like this:

enter image description here
Source Preventing downtube cable stops from sliding out of place

Answer: "maybe" internal routing, but realistically those are going to be some short sharp bends in cable, and they will very likely rub on the axle.

Both Problem Solvers and Origin8 have modern versions of these clamp on cable stops.

Or check out What's the strongest way to bond a cable stop to an aluminum frame? to see many different ways people have made their own, some prettier than others.

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    Thanks! For the purposes of this question I think this answers it (how would I route the cables externally? Probably with these clamp on cable stops). Although I'll have to measure the diameter of the downtube and see if I can find one that would fit. Commented May 27 at 2:16
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    To add to this, I've seen many old frames with suspicious holes like these, but so far it has always been either (1) a hole to allow the pipes to breathe and not trap moisture, or (2) internal routing for a wire from the dynamo to front and rear bulbs. The interesting bit here is there is just one wire, and the metal frame is used as the return path for the electricity!
    – jayded-bee
    Commented May 27 at 9:07
  • @DillonChan this answer is mostly obsolete now - I suggest you wait for a better answer and accept that, or write your own. Based on the new photos, internal routing is definitely more likely than I first thought. Give it a go poking some spare outer cable sheathing through these holes and see how they go. Good luck, take photos !
    – Criggie
    Commented May 27 at 11:07
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I've been looking for pictures of bikes like yours to provide clues. Pictures of your whole frame with clarity on the decals might provide clues to enable identification and identification might lead to better clues..
The question says the frame is a Coppi possibly from the 80s. I found a couple Coppi catalogs, one from 82 and the other from 99.

These pictures were designed to sell bikes, not to determine how cables are routed but they offer clues.

Here is one of the bikes from the 82 catalog.
enter image description here There is no internal routing on any cables. Shift cables are bare (no housing) and run what looks like (wish they had better pictures) under the bottom bracket. Rear cable has just a little housing (that is hard to see) just in front of the derailleur.

Here is a picture of an 80s Coppi bottom bracket with a routing plate.
enter image description here

By 99 the bikes had changed quite a bit. Here is one of the bikes from the 99 catalog.
enter image description here
In 99 cable routes are roughly similar - no internal cables.

However...
In the pictures provided in the question I would expect to see more cable routing provided and it's not there.
Either there was a plate of some kind that is missing under the bottom bracket,
Or there was some other solution.

In any case, you have a bike to build. My suggestion is to look at what parts you have access to and create your own routing. The bottom bracket routing clamp Criggie has pictured is a good option.

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If you wish to install a cable guide and utilise your existing frame fittings, any plastic under-bb-shell mount part will do, but you will have to drill (in the middle of the C cutout) and thread (tap) a hole to bolt this part into. It's an easy job but will permanently deface a unique part of this frame (which is admittedly invisible except when the bike is inverted).

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