Trim that hose
Sometimes new disc brakes require a hose trim while setting up — here’s how.
Need to know
- TIME TAKEN: 30-60 mins
- DIFFICULTY: Medium
- TOOLS REQUIRED: Allen keys, Torx T25/Centrelock tool, Hose cutter/sharp blade, Insert tool/hose clamps and plastic mallet, bleeding tools, brake fluid
Most disc brake units now come preassembled, with a fully bled system and an extra-long hose. By doing this, the brakes are guaranteed to fit even the largest frame and will work as intended, straight out of the box. However, if your frame is smaller, the excess hose will need to be cut down and the system may need a bleed.
Shortening the hose, such as when swapping the hoses between levers, may seem like a daunting task, but the process is relatively simple and mess-free if you do it right.
In this guide we’ve fitted a new Shimano XT disc brake, and cut down the hose by about six inches. We had to fit a new olive and barb into the hose, but these tiny spares are included with all Shimano brakes and, for that matter, most other brands. The only difference between brands may be the bleeding process, and how the insert actually fits into the hose — Shimano uses a press-in barb, while SRAM uses a threaded design that screws into the hose.
In most cases, you should be able to fit the new hardware and get up and running without needing to bleed the system, but if you’re working on an older brake, or have been particularly slapdash with the hose trimming, you may have to remove a small amount of air from the lever. We’ve gone through the process in the second half of this step-by-step.
1. Remove wheel. Take the brake lever and mount to handlebar on the correct side in the preferred orientation.
2. Take caliper and feed through frame or down the fork legs, ensuring the hose follows the correct routing.
3. Mount caliper, ensuring bolts are a half-turn from fully tight, and brake mount (if required) is in correct orientation. Zip-tie or clamp the brake hose in place.
If you have a full-suspension bike, measure the hose length with the bike fully compressed. You may have to remove air from the rear shock to do this.
4. The extra hose can now be trimmed at the lever end. Remove rubber cover at lever end and undo 8mm compression nut. Hold rag underneath in case of spillage.
5. Slide rubber cover and compression nut down hose, out of the way, and pull hose from lever. Try to be gentle to avoid spillage, but some hoses do require a sharp tug.
6. Hold hose in shorter position next to the lever and turn handlebars 180 degrees. Ensure that hose length is as short as can be, while achieving full steering/suspension travel. Mark the length.
7. Cut the hose using hose-trimming tool.
No specific cutting/insert tools? Very carefully use a sharp blade for cutting, and use hose clamps and a plastic mallet for the insert.
8. Take new compression olive and slide onto hose. Press the insert into the end of hose using either an insert tool, or hose clamps and gently tapping in with a plastic mallet.
9. Apply a miniscule amount of grease to olive and push hose back into lever. You should feel insert bottom out inside lever.
10. Holding hose in place, slide up and hand thread the compression nut. Fully tighten nut to 5-6.5 Nm to compress olive. Refit rubber cover.
11. If you need to bleed the lever — remove bleed port screw on lever. Ensuring ‘plug’ is fitted, add a small amount of oil to Shimano bleed bucket, and fit to lever.
Flick the hose with your finger while pumping the lever; this will encourage any air in the hose to migrate up to the reservoir.
11. Remove plug to open bleed bucket/reservoir and pump lever. You should see small bubbles rising through oil from lever. Pump the lever until bubbles stop appearing.
12. Fit plug in bucket then remove from lever and place out the way — be careful of spillage. Refit lever bleed port screw and nip tight to 0.3-0.5Nm.
13. Fit new rotor to wheel and refit wheel.
14. While holding brake lever, tighten caliper bolts to align caliper, repeat if disc is rubbing constantly.
15. Finish by checking all bolts are tight. If this doesn’t work, align by eye and tighten bolts a little at a time to avoid caliper moving.
Shimano Tl-BH62 Hose Cutting/Insert Tool £79.99
This is a great little device; one section of the tool will cut the hose precisely at 90 degrees. The other section clamps the hose without damaging it and the lever presses in the insert with minimal effort.