Internal cable routing (internal tubes) pros and cons
 

I am currently trying to decide between a couple of different internal cable routing options.

1. Internally routed full length outer cable housing for derailleurs, and hydraulic hose (obviously). - with just plastic cable guides on the entry and exit spots on the frame.
https://encrypted-tbn0.gstatic.com/i...ccxJc&usqp=CAc


2. Internally routed inner cable for derailleurs, and a hydraulic hose. - with cable stops on the entry and exit spots on the frame (but not full length cable housing).
https://bikerumor.com/wp-content/upl...able-stops.jpg


3. I am not sure what it is called, but the last option I am considering is when small tubes and are brazed inside the main tubes for the purpose of internal routing. I am not sure if this option normally has full length cable housings or cable stops.
https://www.btr-fabrications.com/wp-...nless_Tube.jpg

I am not sure of the pros and cons of each internal routing solution, ie how much more would option 3 weigh, would I experience any rattle or banging with any of the options, would using full length outer gear housings make shifting poor. Any feedback would be greatly appreciated thanks.

Did you try to paste an image or something?

Very few people use just a grommet on a metal frame any more because so many of them failed when it first became popular to do that. I think most framebuilders put a full length piece of tube that will clear housing. I'm sure you can get the two stops connected by a small brass tube, but probably only from Ceeway at this moment in history. Nova might have them when they come back

Aside from aesthetics, I can't think of any good reason for internal routing. All of my frames are built for full length housing, run externally. I have not noticed any shifting performance issues from the full length housing.

Why full length rather than having an exposed bit of inner along the TT and both sides of the DT? I've always done this for no particular reason other than it's what I had on my existing bikes.

Mostly because they are gravel or MTB frames and the full length housing keeps dirt and water out of the housing. Partly because I was hit by a car and the exposed cable, on the downtube of my road bike, caused a 3" laceration on my knee

For sure the hole in the frame must be reinforced in some way, externally or internally. I do not care for internal routing as it offers no advantages as far as I can see, but present unique challenges as a builder and for future maintenance. Even my mountain bikes have the old school exposed cables and they offer no problems. Of course I do service the wires with clean and lube once a year. With external stops it literally takes no more than a minute for each line. Super simple. If that were to be done with internal cables it is much more time consuming, enough so that it is avoided, and called "maintenance free", although it is not.

For weight weenies, internal routing or full length housing externally costs grams. No good for the weight watchers!

Part of it is also aero obsession.

The industry has gone to internal routing because being a bike mechanic was previously too easy

I laughed at this.

On the plus side, people are actually being paid to work on bikes now.

My reality blames the marketing depts for any design that makes no mechanical sense:) The industry does need to create demand for what the riders don't already have. Like stats or politics it's easy to make claims, state certain numbers and pay a pro to ride what you make and in a manor attribute any "gains" (self defined) to be from the "new thing". Andy

There is no doubt customers like hidden cables. It might have as much aero effect as shaving your elbows

internal routing does a better job of preserving the paint job on the (sometimes underside, sometimes semi-underside, sometimes top of the) top tube.
makes a difference when you're buying a vintage frame.

What's to not like from a customer point of view? If they had to actually drill unnecessary holes in their lovely seamless steel tubes themselves they might see the aesthetics of the whole thing differently.

Decades ago I recall at a bike shop I worked at that a bike had internal routing for something, and I remember some very upset mechanics trying to feed a cable through it.

I am content to have my cables external, but I could see a role for internal routing the taillight wire on a dyno powered taillight.

seems that a lot of the current internal routing trend is for Di2 with brake cables following

I had a miyata 1400 that cracked at the internal routing hole.......this was before they realized they needed reinforcement.....so based on that I would avoid internal routing