Garage Files – How to Trim a Brake Line Without Bleeding It
Hydraulic brakes are the best way to slow your bike on the trail; however, they’re intimidating for many riders who insist that cable-actuated brakes are more reliable and easier to work on. In reality, hydraulic brakes are more reliable and easier to work on than any cable-actuated brake system.
Nearly every new bike comes with hoses that are longer than what’s actually needed. While hydraulic brakes don’t necessarily need to be trimmed to function properly, there’s no reason to have loops of excess brake line hanging off your bike, waiting to snag on branches and send you promptly to the ground. It’s an easy procedure to trim your lines down, and the steps are nearly the same on every major brand of brakes out there. We’ll show you in this month’s “Garage Files” why there’s no excuse for riding with an extra “squirrel snare” of brake line hanging off the front of your bike.
1. We’re going to shorten the rear brake hose on our Intense Recluse bike, which uses SRAM Guide RS brakes. It should be noted that before you try this procedure, it must be done cleanly, or your brakes will need to be bled afterwards. Take caution if you have little or no experience with hydraulic brakes.
2. Begin by removing the rubber piece that covers the brake-hose compression nut, and slide it down the hose and out of the way.
3. Use an 8-millimeter open-ended wrench to loosen the compression nut. This should not be a very tight nut and should break free relatively easily.
4. Once broken free, you can use your fingers to spin the nut completely free. Once completely unthreaded, slide it down the hose and out of the way with the rubber cover.
5. Most brake hoses are pressed into the lever and will need to be wiggled free. Be careful when doing this, as you want to minimize the amount of fluid loss.
6. Now it’s time to measure the proper hose length. Keep in mind the hose goes about a centimeter, or roughly half an inch, into the lever where it will be clamped in place.
7. The proper hose length should be short, but not so short that it will pull out in the event of a crash. We like to take our measurement with the bars turned like this to give it plenty of room should the bars turn in a crash.
8. Brake hoses can be easily cut with typical cable cutters like these. However, this is not the ideal method.
9. As you can see, the cable cutters not only crush the internal tube, but also tend to fray the external portion of the hose.
10. If this is your only option, be sure to clean the frayed ends as well as possible, and then use a scriber to gently open the internal portion of the hose up.
11. The professional mechanics use a special tool, like this one from SRAM. It’s essentially a razor blade that works like a guillotine to precisely trim the hose.
12. As you can see, the hose is still perfectly round, and the internal portion of the hose is unfrayed.
13. If you don’t have a fancy brake-hose cutter, a utility knife on a workbench provides the same precise cut. The only downside to this method is that you must be working close to a workbench you don’t mind marking up, and the cutting requires a lot of force.
14. Once you’ve successfully cut the hose—and hopefully not the skin on your hands with a slipped razor blade you’ll notice the cut is as clean as, if not cleaner than, the one done with the professional-line cutting tool.
15. Now we must install our fresh mounting hardware. All brakes use a compression fitting, which is usually referred to as a “barb and olive.” They can be purchased for less than $10 from most any shop. Reassemble the fitting kit the same way it came off. The rubber fitting and compression nut will already be on, so simply slide the “olive” onto the hose.
16. Now it’s time to install the barb. Our SRAM barb comes with a handy threaded piece that can be screwed into the hose using a T10 Torx fitting. If you’re using Shimano or another brake brand, the barb may need to be hammered in.
17. The barb must be fully inserted into the brake line to ensure the hose will hold in place under high pressure (when you really need the brakes to work!). Be sure the head of the barb is mounted flush with the end of the brake hose.
18. Now, with the fitting kit fully in place, it’s time to insert the hose into the brake lever. If you’ve done this quickly, you will not have lost much, if any, fluid.
19. Push the hose all the way in until the barb bottoms out on the inside of the lever. This is where it will be compressed into place with the compression nut.
20. Now, while holding the line in place fully inserted, thread the compression nut into place until it begins to snug. This is a terrible nut to cross-thread, which is why we’re using our hands first and a wrench next.
21. With the compression nut engaged, it’s time to torque down the compression nut. This is not a high-torque nut and will not require more than a turn or two. It’s very important to note that the compression nut will not fully go into the lever and will leave a few threads exposed. This is normal. The torque rating for this nut is between 5 and 8 Newton meters.
22. Slide the rubber cover back in place and give the lever a couple of squeezes to check your work. If you’ve done the procedure properly and quickly, the lever should feel almost exactly as it did before you started. If it feels squishy, you’ve introduced air into the system, and the brake should be bled before riding.
23. With the brake hose cut to the proper length, you should now have your cables coming off at roughly the same angle and curve. We like to use a couple zip-ties to hold them together. This not only makes them look cleaner, but also keeps them from rattling when on the trail.
24. As a style bonus, we like to face all the zip-ties the same way and then trim the ends with either a pair of flush-cutters or a fingernail trimmer. This ensures that there are no sharp or jagged ends hanging off.
25. All of our cables are now set to the right length. It’s time to hit the trails.
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