I'm getting ready to run a rear brake cable through the top tube. It's an inexpensive SS, and I intend to simply drill two holes in the side of the TT front and rear...but then comes the part about trying to locate and fish out the end of the cable once I have it threaded though the front hole. Maybe a piece of wire first? Please advise. (This is my first post on Bike Forums, so treat me gently.)

There's a lot of bad juju that comes with drilling a frame. Are you a framebuilder? I think threading the cable is the least of your worries.

please put down the drill...
https://www.cambriabike.com/shopexd.a...N+CABLE+GUIDES

Drill first ask questions later.

Lets assume that you already have a frame with internal cable routing holes because, of course, we would not condone drilling your existing frame. In that case, you would run a derailleur wire into the front hole towards the back and then after removing the seatpost and sticking a fabricated long nose pliers into the TT you would steer the wire out the back hole. Then you would clip the stop end of the derailleur wire off and run your brake housing through each hole guided by the derailleur wire.

Easier method: Measure the distance between holes with the cable housing and run it through about two inches short of that. Use a small pick, awl, or clothes hanger wire to find the end of the housing then stick it in the hole and bring it out.

Stop. Stop. Stop.

I'll try to be gentle. Clearly you have not thought this through.
Take the time to look at a bike that actually has thru-top-tube cable routing. you will see that it's not a matter of simply drilling a couple holes in the top tube. The cable/housing enters and exits at a very shallow angle through a special piece (boss, fixture, braze-on, whatever). There is normally a "tube within a tube" here. The cable/housing isn't simply in the open frame tube. I currently have a steel framed bike with internal cable routing and this is how it is made. I used to own an aluminum framed bike with internal cable routing and it was much the same.
Doing as you suggest, well, you would have the cables entering/exiting at a 90 degree angle which would not only look like crap, it would put an extreme bend in the cable which would have a very adverse effect on your braking performance. Your inexpensive SS frame would be basically worthless at that point. I wouldn't even do this to a Wal-mart POS. Anyone looking at your DIY "project" would have to quickly turn away for laughing hysterically.

Please stop.

Run the housing full length. You can use a zip-tie or plastic housing clamp on guides to keep it in place. All you're doing with internal cable routing is creating a headache for yourself when it comes time to change it, and also another place for water to get into the frame.

Assuming you can even modify your frame properly that is.

Another question - why do you want to to do this? Are there no braze ons for a rear brake? Solution: aforementioned zip ties or take the bike to a framebuilder and for around $20 they'll put them on.

Or are you trying to get a smoother look? If that's the case, buy a nicer frame that has internal cable routing.

I will gently add my voice to the chorus here: DON'T DRILL YOUR FRAME!

If you, for some insane reason, decide to do this, there are several posts on various internal cable routing techniques.

This is the most compelling posting. You can't just drill a couple of 90* holes and thread the housing through.

I have a '92 Trek with the rear brake cable factory run internally by Trek and, even though the holes are drilled at the proper angles and the transition guides are in place, it is a PITA to deal with.

The Italians had it figured out some time ago. There's an internal guide inside the tube on this frame, it makes running new cable and housing easier than it would be without internal routing. Mostly, I think, it adds a bit of flair to the bike:

As much flair as you can get with an external bb crankset and shimano pedals on a pinarello anyways.

Uh, no. And thanks.

no

Ah, so more flair than some slave to the almighty "purism" that runs what they want and doesn't give a crap what other people think? I agree.

https://www.youtube.com/watch?v=f8fbrUjjivw&eurl=

Thanks for all the replies. I quess I should add a little more info on my (maybe) project. I am not a frame builder, but I'm pretty experienced at metal working. The frame I am thinking about modifying (okay, butchering) is a steel Raleigh Rush Hour, several years old. This frame originally came with plastic cable guides which were stuck on the frame with double sided tape, and of course they were removed by original owner who only rode it as a fixed gear. I bought the frame from him for $20, so if I end up ruining it I'm not out too much. (I own nine other bikes.) To allow the cables to go in and out of the top tube at an angle, I had planned to make the openings oblong. I had also planned to silver solder some sort of hoods over the openings similar to the ones in the photos posted. One worry I do have is that the holes might weaken the TT, and after a little research I see that the professionals do not put the holes both on the same side of the tube as I had originally planned. (If I ever get this project finished, and if I ever buy a camera, and if I ever learn how to post photos, I'll show you all how it turns out.)

In case anyone's wondering what the pedals are in the earlier post, they're Campagnolo Chorus. As is usually the case, "operator" is the know-it-all who doesn't know what he's talking about.

The point that I think you're missing is that the "holes" aren't simply holes, "hooded" or otherwise. With the connecting tube inside the TT, "fishing" the brake cable through is not even an issue. You simply push the cable and housing in the front and it comes out the back. Nor is it an issue of exposing the inside of your TT to the elements and inviting rust to start. The interior of the TT is still basically closed to the outside. I'm not into SS or fixies, but the Rush Hour still seems like too nice of a frame to do this to. My suggestion is to just get some new cable guides and go from there.
All this begs the question, if you have experience and conviction in the project, why did you have to ask in the first place? Just curious.

well biked, I think your bike is stunning.

Thanks.

Jeez people, the man wants to tweak a $20 frame. Let him have his fun.

lfw,
The "holes" are not on the same side of the tt because of the angles that would work best for the housing. The front will usually be on the lower left side quadrant and the rear on the upper left quadrant. Those locations give it the right bend for entry and exit.

I have an early nineties Paramount Series frame (made in Japan) with internal routing and no guide tube. They were lower end frames with a braze-on hood over the holes. This hasn't been a problem.

Well, if you insist, you may as well do it right.

Several people (including me) said he shouldn't... nobody said he couldn't.


Awesome link BTW! Thanks.