Shortening brake hoses involves dealing with brake fluid so wear gloves. They look stupid and feel clumsy but then again so do brake fluid burns.
The brake hoses supplied with new brakes are almost always longer than you need, so that they can fit all sizes and types of bike on the market. Trimming them down keeps the bike looking tidy and also reduces the chance of the hose getting caught on trailside foliage, which can cause you to crash and possibly damage the hose, leaving you stranded and brakeless. As with every cutting task, it’s better to measure twice and cut once than vice versa but if in doubt err on the side of caution, as whilst it’s easy to remove more from a hose, you won’t be able to lengthen one you’ve already cut! It’s best to use new olives every time you refit the hose – the old ones often become deformed when you remove them, so make sure you have all the fittings you need before you start the job. Ideally, when doing this job you’ll make a neat slice in the hose, then refit it without losing any fluid. In practice; this is easier said than done, so you may find you need to bleed the brake once you’ve refitted the hose.
Step 1: Undo the shroud and push it along the brake hose to reveal the hose fittings, including the olive and copper crush washer. Slide the shroud down the hose, beyond the point at which you’re going to cut it so that you don’t have to refit the shroud to the hose.
Step 2: The hose should come free of the lever easily, so avoid pulling it sharply and flicking brake fluid out of the hose, letting air in. Instead, ease it gently away from the lever.
Step 3: Cut the hose with a sharp knife at your chosen point, discarding the redundant fittings. Check that the cut is clean and the hose opening is tidy – you may need to remove any small pieces of outer sheath or inner weave to get a neat hole.
Step 1: Making sure that the shroud is still in place on the hose (it’s surprisingly easy to drop it on the floor without noticing), fit the new olive and then the new barbed fitting into the end of the hose. Take care not to bend or damage it – it’s relatively soft so don’t hit it. Instead, gently work it into the hose until it’s flush with the cut face. Fit the new copper crush washer to the end of the barbed fitting.
Step 2: Offer the new fittings up to the brake lever, then pull the shroud back into place over the whole assembly.
Step 3: Tighten the shroud, at first using your fingers to screw it back into place and then using a crescent wrench to tighten the last few turns. Make sure you don’t overtighten it, as this is likely to damage the threads, but equally don’t leave it loose as this can allow fluid to leak from the system. Test the brake by pulling the lever a few times – if it feels soft or mushy and the brake has lost its bite, then air has got into the system and you’ll need to bleed the brake.
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES