Running a Brake Line through a Frame without Internal Guides
I don't harbour the same white-hot hatred of internally-routed brake lines as many, but I won't deny they are a colossal pain in the ass. This development takes the relatively simple job of installing or replacing a rear brake and adds several levels of complexity and hassle, and a minefield of potential setbacks. A brake bleed is all but inevitable, and you'll need to shorten your brake line, whether it needs it or not, because you'll need to reinstall a new olive and insert, into the newly cut line. If your frame has tube-in-tube construction to guide the line from one end of the bike to the other, inserting it into the frame can be straightforward. If it only goes partway, as in the Norco Sight VLT I recently wrestled with, it's less helpful. If there are simply ports for the brake line to exit and enter the frame, with no internal tubing, both on the mainframe and in the swingarm, you're in for more of an adventure. You'll also need to take some precautions to prevent the line and cable housing(s) from sounding like a cracked-out marching band clattering around the inside of your frame.
If you were a smart racer, in the days before internal routing, and you had trouble with a brake on race day, you could have one already bled and cut to length and slap it on in five minutes. Now it's likely an hour unless you are a trained mechanic which means you are going to need a spare bike if the turnaround time is too short.
I have used the installation of internal lines and cable housing, without any special tools, as a sort of personal DIY challenge until this point, but the full-day build* of the We Are One Arrival frame, which I'll be using as a test platform, finally convinced me to get with the times. I’ve had several other adventures with internal routing lately, both with the Norco Sight VLT and the SCOR 4060 LT. Almost as soon as I'd built the aforementioned Arrival, and installed a set of SRAM Code RSC brakes, a pair of Hope Tech 4 E4 test brakes, which I expected to wait months for, magically appeared. I had Macguyver fatigue from the build a week earlier and I decided it was time to buy some skills in the form of the right tools.
*not entirely because of internal routing but partially
I knew of Park's internal routing kit but when I looked it up online I was a little put off by the price. Their kit, which includes a powerful magnet and four coated wires, sells for about 115 CAD. The coated wires have one magnetic end and the opposite ends are designed to attach to different types of hose, housing, and wires so these can be yanked through the frame.
The idea behind this tool is relatively straightforward. Once the magnetic end is inserted into the frame, you drag it along the inside of the structure, from the outside, using the large sceptre-shaped magnet, assuming your frame isn't made of steel. This sounds tricky but if you lose contact with the the end inside the frame it's obvious, because the magnet in your hand no longer sticks to the frame. But you are correct, it's a little tricky. Once the magnetic end emerges from the exit port, you attach your cable/hose/wire to the trailing end and then you just need to pull the whole thing through. It’s as easy as juggling live eels.
The price of the Park tool likely makes sense for a bike shop, but I figured there might be a knock off on Amazon. I have little affection for Bezos's company and, in particular, its labour practices, but I am a sucker for convenience and cheap prices. I found the "Wallfire MTB Internal Cable Routing Tool Internal Cable Routing Kit for Bicycle Frame Cycling Accessories Bicycle Repair Tool Internal Cable Routing Kit for Bicycle Frames," for 27 Canuck bucks and bought it with one click. Which is actually two clicks. Clearly being deceptive about the number of clicks is profitable. And profit, as you may know, is everything.
When I put a set of SRAM Code RC2 brakes on the Arrival, I attempted it before the fork was installed. Unlike Hopes, a SRAM brake line must go in from the rear of the frame because the banjo at the caliper end, which helps seal the line's connection, cannot be removed and replaced like the lever end (at least not by me). Using the void of the head tube for access, I was able to steer the brake line out into the fresh air, after a relatively long and frustrating struggle. With the fork installed I would not have been able to find the exit port at all. Even with that advantage, it was a tricky proposition with many frustrating detours, for both main frame and swingarm.
Part one of the process with a tool like this is to use the guide magnet on the outside of the frame to pull the entire wire through. Or, if you prefer, you can do the swingarm on its own and then proceed to the main frame. Because of the smaller structure, the swingarm was relatively easy. You just drag the magnet along the outside, careful not to scratch the frame's surface and to stay in the middle of the structure so the inner magnet can move more easily. One you get to the main frame, there may be other housings and their zip tie tales to navigate. Because I used an AXS rear derailleur, I only had the housing for the dropper post to avoid. I found that the guide magnet used to pull the wire through the frame could have been stronger and a few times I lost contact with the wire. It was easy enough to find it again and continue the process but a stronger magnet would have been helpful. At this point I still had a smile on my face.
The next step in the post-magnet-system era was easy, or at least it should have been easy, but I was too hasty. More than once. I managed to get the line through the swingarm and then the mainframe only to discover I needed to start again for one reason or another. In the first instance, I attached the brake line only to discovered that the diameter of the braided line is slightly larger than a standard brake line and it was too big for the wee hole. Instead of pulling the green wire all the way out, I decided to pull it out of the front of the swingarm and then pull it back through once I was ready using the other coated green wire. I gently took a round file to the rearmost port and shaved a few micrometers off until the hose would just slide through.
At that point I realized that Wallfire (the sort of fire you'd prefer not to have) had bamboozled me. The kit was supposed to have come with three green-coated wires, as advertised on Jeff's little boutique website, but mine only came with two. There was supposed to be a third line with the opposite polarity of the other two, designed to pull either of the others through, if necessary, without a hint of drama. Instead I received only two, each with the same polarity. Luckily, the end that bores into cable housing or brake line, can be mated with the two-piece end aimed at pulling Shimano Di2 wire (are there other companies making wired components?) through a frame. And actually, the connection was better than a magnetic one would have been.
Finally I was back to the point where I could pull brake line through cavernous carbon fibre voids the way a charmer entices a serpent to dance. I was all set to pull it through when I realized the shroud, which should have been removed long before anything had been strung through the frame, had slid all the way back to the caliper. Once that was removed I was ready. Almost. I then noticed that I had somehow pulled the entire wire out of the head tube so it was no longer in any position to aid my cause. Eventually all that was sorted and it was on to the next challenge.
If you are about to pull tubes into a carbon fibre frame without tube-in-tube construction, without any noise mitigating strategies, be prepared for your bike to sound like a tiny baseball bat banging around in a garbage can. It's awful. The only thing worse, and also a great April Fool's prank, is when one of the tokens in your buddy's fork comes loose and slams up and down with every compression. But this is a close, and more difficult to resolve, second. There are several ways to prevent this horrendous outcome but I've discovered on that has thus far been foolproof and relatively simply.
The idea is to secure zip ties around the housing or hose in question, with their tails intact, and then wrap it around the particular tubular structure as tightly as possible for insertion. At this point you should have a coil, as cute as a piglet's tail, curling around the long, thin, conveyor of wire or fluid. You may have already surmised that this plan is dependent upon the presence of a port at the bottom bracket, or at worst, the absence of a steerer tube. This is the sort of process best not left to chance. I firmly secured two zip ties around the brake line, (the last few remaining from the pack of 1000 I purchased in the late 90s,) after it had emerged from the swingarm. I was far too proud of myself for remembering to do this, which undoubtedly impaired my ability to estimate where the frontmost zip tie should be attached. I managed to navigate the end of the brake line through the port on the head tube, only to discover that the first zip tie was too close to the end of the line, preventing it from pulling through all the the way to the brake lever. In fact it wasn't moving. At all.
The positive about an embarrassing error made while maintaining your bike, particularly when you announce it publicly, is that you are less likely to reproduce the same error in the future. And I am getting to the point in my recently elevated DIY career* where I feel like it's time my batting average gets into the .350 range but I'm not there yet.
I pulled out the hose once again, and manhandled the too-tight zip tie into place, approximately 1/3 the way down the down brake line, to balance the other tie.
*It's not just bikes - I've been inexpertly fixing dishwashers, driers, our fridge, my new-to-me 16-year old car, a broken HDMI cable, doing a little plumbing etc. I've avoided tackling most of these sorts of tasks until this point in my life but I'm enjoying leaning into them now.
Pieceofmotherfuckingcake, I said to myself, far too soon. It was time to focus my gaze on the finish line and then I realized I had forgotten to install the two rubber grommets, provided by We Are One to help create a seal at the front port of the swingarm and the removable rear port of the main frame, right around the bottom bracket. I cut the zip ties off and rolled these into place, which is another somewhat frustrating task. At first I was trying to pull the inch-long grommets along the line but they are quite sticky. Rolling them like donuts is much faster. Finally I placed two new zip ties securely and more accurately onto the line, once again screwed the threaded cone end of Akantor AK 320 installation wire into the end of the line, and pulled it into the hatch at the bottom bracket.
The last step was to repeat the process of getting the braided line out of the frame on the non-drive side of the head tube (for those of us who place our rear brake lever on the drive side of the frame). This is a little finicky and I was a little worried about pulling everything through the second time with the long zip tie tails on the brake line but I eventually was successful and all that was left was to cut the line to length and bleed the system. I have a couple of different tools for cutting brake line, both with a guillotine-action, but they were useless against the metal mesh of the braided line. I used a pair of housing cutters, which was a bit like a hot knife through chainmail be eventually successful, and then I grabbed a sharpened spoke to open the internal hose of the line that had become crimped in the process.
And Bob is your mother's brother!
Give it a try. If I can do it, you surely can. Or if you are an expert in this area and have some tips, please share them with us.