How to flare stainless steel brake lines in place
Hard stainless steel brake lines frequently crack or slide out of the tool when attempting a bubble flare. Because the tool must be clamped in a vise and cranked down extremely tight, successfully flaring a new coupling directly on the vehicle is almost impossible.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
How to flare stainless steel brake lines in place
- 1Running a whole new line using copper-nickel tubing, which is softer and easier to work with.Did this help you?
- 2Cutting the line further back (4-12 inches) to a more accessible spot and installing a new section with a union.Did this help you?
- 3Switching to much softer copper nickel brake lines instead of using steel or poly-coated lines.Did this help you?
- 4Putting the flaring tool block into a bench vise and cranking it down extremely tight to prevent slipping.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“I cut the line, deburred, lubricated, and attempted doing a bubble flare, however it just turns out like this every time.”source ↗
“I’ve watched like 20 videos and they’re just doing the exact same thing that I’m doing.”source ↗
“That poly armor stuff is super hard to work with. It slides in the tool that's where all those silver marks are coming from. I used to put the flaring tool in a vise then crank the tool down stupid tight to flare it. Even then I had mixed results.”source ↗
“Dissimilar metal corrosion between the brass on the hose fitting and the stanless lines, rotted out the steel coupling. Any ideas?”source ↗
“Any way to cut the line and flare a new coupling on? I read its an issue with stainless.”source ↗
“Have you flared stainless line? I have read its prone to cracking. And hard to do in place, not in a vice.”source ↗
“hard steel lines can be a real headache”source ↗
Where this came up
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