Garage Files – Saving Carbon Frames
Internally routed cables seem to be the norm and not the exception in the mountain bike world now, especially if you’re looking at carbon frame models. Until recently, however, nobody had figured out an efficient way to route internal cables. Mechanics were stuck peeking into tiny holes with flashlights, trying to fish the hose through. With some of the older models, it felt a little like trying to throw a hot dog into a wine bottle from 10 feet away. Now, however, internal routing has improved to the point where you’ll not only find it on top-end race bikes but also on mid-and even some entry-level models. Over time we’ve learned a few tricks to make routing internal hoses easier. This is the procedure we use.
1-We’re going to be installing a Shimano XTR brake on a Pivot Mach 429SL. The procedure is essentially the same no matter what bike or brake manufacturer you choose to use.
2-Start by attaching the brake caliper to the frame using the proper bolts, hardware and adapters.
3-Then, find a piece of brake housing that’s approximately the same length as the brake hose the bike will need. This “dummy housing” will be used to guide the actual hose through the frame.
4-Now, run the dummy housing through the internal frame routing.
5-Our Mach 429SL has cable guide clips that need to be removed to aid in the routing of the brake. If your frame has a similar setup, remove these clips and put them in a safe place. Then, use a pick to gently “fish” the dummy housing through the frame ports.
6-SRAM makes this nifty tool that will also aid in the routing of the brake hose. It’s a threaded piece of aluminum that’s designed to “tie” the dummy housing to the brake line. This makes it easy to pull the hose through, and simultaneously plugs the line to prevent fluid loss. This piece is included with Reverb seatposts and can also be ordered directly from SRAM.
7-Thread the SRAM hose plug tool into the dummy housing end on the rear of the bike. It will be used later to pull the hose through towards the lever.
8-Disconnect the brake line from the brake lever using the appropriate-sized open-end wrench. For this XTR brake, it’s an 8-millimeter wrench. It may require a little wiggling to free the hose from the lever once the compression nut is removed.
9-Nip off the end of the hose to remove the barb and olive that are compressed onto the brake line. These must be removed to clear the ports on most frames and also to utilize the SRAM hose plug tool.
10-Now, use the SRAM tool to connect the dummy line to the actual brake line. You can use a scriber or similar tool through the small hole in the middle to spin the tool and thread it in.
11-With the two lines now connected, pull the dummy line out, and the brake hose will follow through the internal routing.
12-For the Mach 429, now is the best time to replace the covers that hold the brake line in place.
13-Install the brake lever on the handlebar in a place close to where you think you’ll be running it. You don’t have to be precise down to the millimeter right now, but it should be close enough to take an accurate measurement for the hose length.
14-Disconnect the two hoses by unthreading the SRAM plug tool from the dummy housing.
15-Now, measure your brake-hose length by routing it to the lever. The hose should be long enough to not be pulled out in the event of a crash that spins your bars, but not so long that you might snag the hose while riding.
16-It’s time to cut the line. Remember to measure twice and cut once with this critical step. If you don’t have one of these handy line-cutting tools, a sharp utility tool will also work well. Cable cutters will get the job done, but can leave a frayed line afterward. The sharpest tool is the best tool in this case.
17-Install the rubber sleeve, compression nut, and new olive onto the line in this order. They will be loosely sliding on the hose for now.
18-Shimano’s brake hose clamp is a great tool to make the installation of the fresh hose barb easy.
19-Clamp the hose in the channel of the hose blocks, then use a pair of pliers or vise grips to hold the blocks in place. Then, rest the edge of the blocks on something solid. If a vise isn’t an option, the stem faceplate will work fine.
20-Use a metal hammer to now gently tap in the fresh barb. It should tap all the way in until the end is flush with the end of the hose.
21-Slide the hose with the freshly installed barb, olive, compression nut and rubber cover into the brake lever.
22-The hose should fully bottom out inside the lever. You can now begin to thread the compression nut into the lever, which will push the olive up along with it. Be careful with this step, as the threads are very lightweight and can be easily cross-threaded. If you have to use a wrench to make the first few turns of the compression nut, you’re not threading it in properly.
23-Use the open-ended wrench to tighten the compression nut. By doing this, you’re compressing the olive onto the brake line and making a seal on the hose. Be cautious to not over-torque this nut. Just a little past snug is right. For the most precise specs, the torque should be between 45 and 60 inch-pounds.
24-Now, check your handiwork by pulling the brake lever to ensure you didn’t introduce any air into the line. If it takes more than a couple pumps of the lever to make it feel right, it’s best to bleed the system to remove that air.
25-Reposition the caliper so that it’s centered over the rotor and hit the trails!
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