I recently took it upon myself to replace the brake line from the block splitter thing by the master cylinder to the rear brakes on a project I have been working on. After ordering brake fittings (14mm x 1.5mm) for 1/4' line. I found that they did not fit by a very thin margin, to remedy this I ran a 1/4' drill through it on my press to no avail, after this O repeated with 9/32' after which the brake line fit with a slight clearance.

My question being is this ok to use? the brakeline has a ISO flare so I figured it will crush and seal the line but I figured I should double check on here.

I included some photos for reference.


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ake l

  • 1
    I have drilled out nuts before without issue. Just be sure they are the correct nut for a bubble flare.
    – Moab
    Nov 6, 2019 at 17:09

2 Answers 2


Either you have the correct fittings with the wrong size pipe or the correct pipe with incorrect fittings.

That "fit" (get a bus through there etc) is loose enough that the pipe can vibrate and so cause the fitting seal to leak over time - even catastrophically.

Get the correct pipe / fittings and make sure it is correct. I used to make my own brake pipes and have the flaring tool for doing so... Never had one fail or leak.


Your fitting will not produce that bubble flare in the brake line. You need a special flaring kit for that. A single flare won't work, has to be bubble flare. You can get them at any auto store. See the picture below. Take the original part into an auto store and get the right parts. You can't be drilling parts to make them fit.... these are your brakes you're talking about. Those fitting come in different sizes and are very close so get the right ones.

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