On Internal Cables

A couple weeks ago I went for a ride, what else is new, on my newest Roubaix. (Pictures to follow). She is very pretty but during my ride I had a lot of trouble upshifting to the 53 chain ring from the 39. I took the bike, hereafter I'll call her Abby, to Malcolm who tightened up the front deraileur for me. (The problem with this bike is, due to internal cabling and the way the original store set her up - they didn't bother to install the barrel adjusters - getting the front deraileur set correctly requires a very skilled hand, in other words, Malcolm.)

Anyway when I got Abby home I set to work on her, Malcolm noticed, with nothing but eyes that Abby needed a new chain. (According to my Park Took chain checker, the wear was at 0.50% or still good.) Trusting Malcolm over a $50 tool that never really did show wear correctly, and the fact that I do have over 3000km on the chain, I tossed my old chain and when I did I could see that the front deraileur cable was unwinding. I had a new task for myself, strip Abby, right to her BB30 bearings, lower the stem a little (the bars were high), replace the bars (I had just bought a pair of Easton EC90s). Swap out her dura-ace shifters and rear deraileur for SRAM Red (I like SRAM shifting more than Shimano) and naturally, replace the cables.

Okay all of the above is pretty standard stuff, except Abby's cables are, as I noted, internally routed. You want the definition of a pain in the rear end, try routing internal cables. Malcolm told me that on old steel frames one would sometimes see guys who had, over the course of their bike's life replaced pretty much every component except that rear brake cable because fishing that cable is so damn difficult. Thankfully, for me, Abby is carbon fibre, so I had a few dandy little tricks I can employ.

First to get the gear cables from the top of the down tube to the bottom bracket I used four items:

1. Fishing line
2. electrical tape
3. A twist tie like the kind that come with small electrical appliances to wrap the electrical cord (those ties are smoother, less friction, than the ties that come with garbage bags)
4. A very powerful magnet (I used one from an old server hard disk drive). SCSI and SAS hard drives seem to have the most powerful of all the hard drive magnets. (Luckily I'm in IT so I get access to lots of hard drives.)

Alright, if you haven't already figured out how I made things work, remember Abby is carbon fibre, not steel. Still not sure? Well first I taped the fishing line at one end to the bars, at the other end of the line I taped the fishing line to the twist tie. Then I inserted the tie into the hole at the top of Abby's down tube and used the magnet (on the outside) to guide the tie to the hole at the bottom of the downtube. Then tape the fishing line (at the end by the bars) to the gear cable and guide the gear cable by pulling the fishing line. (Although in retrospect I should have put off pulling the new gear cable until I had finished running all the fishing lines, also masking tape is cheaper and would probably work just as well, if not better, than electrical tape.)

Now the hardest line to run was for the rear deraileur and this line runs the length of the chainstay, that is from under the bottom bracket all the way to the rear drop out. Now using magnets here is quiet a bit harder. Sure Abby is carbon fibre, but the rear drop out as well as the area surrounding it, in fact the entire join from the chain stay to the seat stay, is metal, I think steel. Ultimately what I did was take an old gear shifting cable, some electrical tape, fishing line and my trusty tie wrap. I used the gear cable to shove the fishing line with tie wrap and electrical tape in from the wrong end - the drop out end - and drive the fishing line forward into the chain stay far enough to clear the steel drop out. Once I could feel the tie wrap with the magnet I used the magnet to draw the tie wrap forward to the hole at the bottom bracket (a very narrow hole at that!) A little bit of the tie wrap would expose from the hole and then using a plyer I was able to pull out the tie wrap and fishing line.

A confession, first I took Abby to my local bike shop and asked them, after several frustrating hours, to do that final run of the rear deraileur cable, but by the time I got Abby back on the stand at home the cable fell out. So I did have to learn the hard way how to route internal cables.

As for the rear brake cable, that was actually very easy, push the cable through the top tube from the hole near the stear tube, once the cable is near the hole near the brake, just use a magnet to bring the cable up and close to the hole. Use a folded tie wrap to loop around the cable at the brake end and push from the stearer tube end while pulling up on the tie wrap. (Sorry if I had a third hand I might have taken some pictures of this step.)

In Computing the most difficult programming task is writing an Operating System, probably the context switches, (hint: push all the registers, interrupt, return from interrupt, pop all the registers) are the trickiest bits of programming. I've heard the for a pianist Rachmaninoff's Third Piano Concerto is probably the hardest piece of music to play. Having routed internal cables, well they aren't the Rack 3, and they sure aren't a context switch on an x86, but damn they were tricky. Maybe next time I'll just take Abby to a bike shop, yeah - as if!