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I have a bike with an internally routed rear brake. I bought Shimano mt200 hydraulic brakes to replace the low end mechanicals that came on the bike. My problem is that the brakes came pre-bled. Now I have them just ziptied to the frame.

My question is, what's the best way to install the brakes? Is there a way to keep the fluid in the lines? Or should I completely empty the lines, internally route, install new olive and barb and then refill with fluid?

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The usual approach is to disconnect the lever nut, cut off the hose just below the factory barb, and then feed it through from the caliper end up to the lever. Then you turn the bars all the way and hold up the hose next to the lever and mark the spot you'll trim to for optimal length. Cut, slide on cover and nut, install new barb and olive, reconnect and bleed.

Some frames have openings big enough to get the nut, cover, and barb through, but most don't. Even if you can do this, the factory olive is smashed up most of the time anyway, potentially causing leaks if rejoined.

The fluid stays in for the most part because only one end gets opened. There are ways of doing the above that introduce little or no air and avoid the need to bleed, but people sometimes overstate how effective those tricks are as opposed to just taking advantage of Shimano brakes' ability to function with a little air in the system. It's better to just bleed it.

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  • So if I cut the hose shouldn't I first drain brake oil out? I think my holes are large enough to fit olive but need to check it first.
    – MT247
    Commented Oct 2, 2020 at 23:41
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    No. A few drops will come out but because the caliper and lever bleed ports remain closed, vacuum holds most of the fluid in. That few drops displaced creates enough of an air gap to make bleeding a good idea.
    – Nathan Knutson
    Commented Oct 3, 2020 at 0:47
  • Ok thanks! Is the bleeding necessary if I don't have to cut the cable?
    – MT247
    Commented Oct 3, 2020 at 11:35
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    It's not totally predictable but you should be prepared to do it. Shimano brakes again have some ability to function with air in the system, it works its way to the lever reservoir, but it's better to not use that capacity up just during setup.
    – Nathan Knutson
    Commented Oct 3, 2020 at 15:22
  • Yeah I ordered bleed kit. I'll wait it to arrive and then internally route my cable.
    – MT247
    Commented Oct 3, 2020 at 15:39
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The J-Kit system is designed for this.

https://www.shimano-tec.com/course/view.php?id=1088

It is possible/likely the brakes you have purchased are j-kit (easy hose joint system), in which case there is a cap which can be pierced; the brake and lever are not connected on supply, and the installation is easier.

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  • I've got these: youtube.com/watch?v=WXI-5BtYR5c not quite sure if it has easy hose joint.
    – MT247
    Commented Oct 2, 2020 at 23:46
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    That link is hidden behind a login that doesn't list many major countries. My local bike shop is Bob's something or other in Kent. Its a lot of rigmarole to go though to see to a two minute video that essentially shows someone sticking a hose in hole. - +1 anyway.....
    – mattnz
    Commented Oct 3, 2020 at 0:28
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    The easy hose joint should be noted on sale. Particularly the supplied hose is -JK- code
    – thelawnet
    Commented Oct 3, 2020 at 7:16

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