jolly_codger

I have wasted almost 2-hours trying to push the rear brake cable housing through the top tube of a Raleigh Technium and wanted to get some input from the C&V frequenters. Please know that I have done this task on other frames with similar cable routing and have never had this much trouble. I have tried greasing the end of the housing & stripping off the first bit of the housing's jacket and have nothing to show for it but a scraped up housing and the growing need to put the Technium in the recycling bin. Question 1 - is there some secret to doing this? I keep teeling myself that they did this on a mass scale when the bikes were produced and I must be missing something obvious.Question 2 - would there be any structural impact if I use a small round file to open up the exit port? I worry because the port is on the cast lug and I have no clue how critical thei lug's cross-section is to functional integrity. I appreciate any insights into my dilemma.
John

Trakhak

Those were frustrating when i worked in a Raleigh dealership in the '80's. Someone else will be along with a cleverer solution, but . . .

Try running the bare cable through first. I used to put a little bend in the last couple of inches of the cable in the (sometimes forlorn) hope that doing so would make it easier for the cable to pop out of the exit hole.

And---I never thought of this back then---you could turn the bike on its side such that the exit hole is facing down. Let gravity help you.

Once you've managed to snake the cable out of the exit hole, run the housing onto the cable and through the top tube, pull the cable out (leaving both ends of the housing sticking out of the top tube, of course), and finish setting up the brake.

Edit: please give us a follow-up post when you've succeeded (I hope) in getting past this roadblock.

Trakhak

By the way, in answer to your first question: I always wondered, too, how they handled inserting the rear cable housing on Technium bikes on their production line. Maybe they inserted a shaped dam that guided the housing unerringly into place and then removed the dam before the top tube was glued into the frame.

If so, it's a shame that they didn't leave it in place for the benefit of shop mechanics and bike owners. A one-ounce plastic dam would have cost next to nothing and saved us a lot of grief.

brewerkz 

I second this strategy

jolly_codger

That is what I am doing and I can thread the housing onto the wire but when it gets to the exit port it just keeps hitting something in there. I've tried starting at both ends and it's the same result. I've pulled a string through and attached it to a small sheet metal screw screwed into the housing (I ground down the screw head to be smaller than the housing OD) to no result. The funny thing is that fishing a bare wire through isn't hard, but it seems like whatever's in there is only slightly larger than the brake cable housing. The frame came with an old housing in there and pulling that out once the inner wire was fed through I could tell it was a tight fit. I will give your idea about turning it onto its side a shot later today and report back.
John

Steel1

I assume you can push the housing on one end from outside to inside the tube (entry port), and its getting stuck on opposite side when trying to exit (exit port).

How tight is it to push the housing into the port?
Can you use a sander and try to taper one end of the housing to help get it started into exit port? Similar to a old school pencil tip?
Did you try greasing the exit port with a toothpick or similar?

Luckily my two internally routed bikes both have some type of internal guide tube brazed in place making it a non-issue.

Kontact 

I installed 105 brakes on my 440 in 1988. I seem to recall putting a cable through the housing with the cable end against the housing end so the cable could be used to pull the housing. Then, with the cable exiting the rear hole, I guided the housing out through that hole by removing the seatpost and inserting my finger into the top tube.

If there is a sharp edge inside, filing it won't hurt anything.

Another trick that would probably work is to have the cable in the housing fished through from front to rear, then take a short piece of housing and start it in from the outside of the rear hole on the cable. With the short housing section butted against the long piece from the front hole, pulling through the rear hole should be easier because there won't be as much of a transition.

Trakhak

I don't remember that problem, maybe because it was too traumatic!

That said, thinking about it, I have a dim (possibly false) memory of using a sharpened spoke to stick into the stuck housing to guide the housing away from whatever's stopping it and out the exit hole. Maybe if you shine a flashlight into the exit hole you can see where the housing is hanging up.

Bad Lag

If it's localized (a burr, scrape or damage), that's one thing. If it is wide spread (corrosion, scratch), that's another.

I have a bore scope with a flexible fiber optic shaft that would fit. They can be gad very inexpensively ($60) and imagery is full HD (1080P). That would tell the tale and lead to the proper remedy.

Of course, you could use the C&V approach and just route the cable externally and use cable clips.

iab

I have heard of the use of a vacuum. Use thread, feed it down the tube the best you can, use a vacuum to suck it out the other hole.

jolly_codger

45-minutes of holding the bike horizontally, upside down, and nose down did not do the trick. I have tried going back to front as well as front to back; some good ideas above that unfortunately I will have to try later in the week because of work travel. I did think about external cable clips or the Origin8 clamp-on cable stops, but I do not want to admit defeat just yet. I did run across a Jagwire "Pop" ferrule in my box of cable-related crap and with a little filing I think one of these at each port would work as faux cable stops if the new suggestions above don't pan out. Thank you all for your insights, I very much appreciate the help!
John

Reynolds 

Since you can get the cable through, but not the housing, I'd try making a cone from plastic with a hole for the cable to act as a guide for the housing.

Kontact 

Did you try removing the seat post or anything else I suggested as someone who has done this?

jolly_codger

Not yet; I tried the gravity idea and later read the newer posts.Lots of suggestions that sound promising but I couldn't get back to trying out anything new. I will get back to it and give everything a go later this week when I am back home after some work travel. Thank you again!
John

Trakhak

Great suggestion. As I recall, the exit hole is pretty close to the seat tube. If it's close enough and the top tube is open at that end, that probably solves the mystery of how they were able to install the cable and housing quickly on the production line.

1989Pre 

Don't modify the exit or entrance for the cable housing. I performed the cable installation recently after I had my Technium resprayed. Put the cable inside the housing and push the housing into the top tube as far as it will go, with the cable protruding about 1" from the end. The only trick is to get the housing/cable through some guide about half-way in the tube. It feels like a rubber ring for vibration insulation. You will feel the resistance, so push through it. Keep at it and it will go. Then, when you see the bare cable coming out of the exit hole at the seat cluster, let it guide the housing up to the hole. The housing might not go through, but I delicately got hold of it with a needle-nosed and that was that.

jolly_codger

Quick update:

Access via the top tube in a no-go; I might be able to get my pinky finger through but there would be zero ability to manipulate the housing (and a strong possibility of slitting my finger on that sharp edge). Heck, with a 25.8 seatpost I can't bend any of my fingers in there even if the end was fully open.

The housing from both ends idea looked so promising at first, but when the new cable gets to the port it just will not go in. The inside opening must be slightly smaller or something because the new housing can go from the outside through either port.

I have a borescope/endoscope coming from Amazon and when it gets here I will try the sharpened spoke guide idea. Maybe seeing what I am fighting might spur some other approaches.

If all attempts to go through fail, it looks like with a little filing a Jagwire Pop ferrule (the stepped down ones to fit into Shimano brake adjusters) would fit into the ports to act as housing stops with the bare wire inside. Or, this may be the ideal opportunity to justify purchasing a 3-D printer to do something more elegant.

Stay tuned, this one ain't over!
John

1989Pre 

Bring it to a bike shop. They have a lot of experience with internal cables.

jamesdak 

I didn't remember having any real problem with the housing when I rebuilt mine. I pulled up the original thread and this came from one of my posts.

" The top tube pass through is one where it is not a solid tube running from front to back. The openings are pretty tight too. I left the old housing in and ran the new cable through. Then I pulled the old housing out and worked the new one through. Inside on the back opening it didn't' want to feed through even with a clean cut. Then when I got to the front opening it probably took about 2-3 minutes of fiddling to get it to feed through that passage."

Sounds like the normal technique worked on my Technium.

Trakhak

While you're waiting for the borescope/endoscope to arrive:

I'm picturing a thin sheet of plastic---not too flexible, not too stiff---that's around 3 to 4 inches across and maybe 8 inches or so long.

I'd roll it into a tight tube and insert it into the housing exit hole. The hope would be that the plastic would unfurl to take up most of the inside diameter of the top tube and form a funnel at the exit point.

Even if the sheet is too tightly rolled to let the inner wire pass through it, the wire would likely be grabbed by the roll and should let itself be guided out the exit hole.

Might have to roll the inner wire between your fingers where you insert it into the entry hole to get it to line up right at the other end.

You could also try a simpler version using a wide plastic straw such as those that some fast food places give you for milkshakes. Split it for several inches starting at one end.

dddd

Trakhak suggested using a stiff wire ("a sharpened spoke"), and I concur with his suggestion.

Being able to apply bending force to the end of the housing using the stiff wire might be key to it's entering what I presume is a sharp-edged hole inside of the toptube.

And some silicone lube on the housing (I use GripShift "Jonnisnot" grease for things like this).

Reynolds suggested a guiding cone at the head of the housing, another great idea imo and not hard to make at the bench grinder.

I have rolls of solid rebar tie wire here that would probably be my first choice (as it is easy to bend), one of which would be just the right diameter and would give me plenty of length to play with.

All of the above said, I recently did a shift cable housing replacement on a carbon S-Works mtb, and the inside edge of the cable housing ports really, really didn't want to let the housing slide into the hole from the inside (the same job on a Santa Cruz carbon mtb would take 25X less time with their convenient internal guide tubes).


EDIT; One last suggestion, if the housing has not yet been cut to just the right length, I would bevel the end of the housing at the bench grinder, lube it up, then cut off the beveled end square after it perhaps makes it out of the cable port (twisting action perhaps facilitating....).

Also thinking that a thin roll of sandpaper inserted into the hole might expand slightly inside of the hole, so as to facilitate sanding away the sharp edge inside. Just don't lose your grip on the piece of sandpaper, or let it tear off inside.

blamester

I used a metal pick. Pushed it past the lip or obstruction and then pushed the outer till it rode up on it. And out by pushing on one side of the outer and pulling the pick back out the other side.

Robvolz 

Magnet on a stick?

Get it near or past and then attract it?

Mooo

I like the vacuum suggestion. Take a thread, electrical tape it to the cable (actually heat shrink tubing has a really small footprint, use that instead), and have some housing around that cable. Stick the thread into the hole, light up the vacuum, once the thread exits the hole, turn the vacuum off and gingerly pull the string until the cable comes out. Then slide the housing out along the cable.

I honestly don’t recall if I’ve done this on bicycles or not, but do remember doing it while trying to fish a control cable down a model airplane and I think I’ve seen it done on full scale aircraft, so not really an original idea on my part. Vacuum nozzle took some thought. Might be worth a couple minutes to see.

jolly_codger

Well, the endoscope arrived, and..........the camera head is too long to get into the top tube via the seat tube. I wlll try to carve out some time this weekend and pull the fork off and pop out one of the cups and see if ithe camera will fit to get into the top tube via the head tube.