Brake Line Flaring Guide: Flare Types, Tools & Technique
A brake line is only as good as its flares. Get the flare right and the joint seals for decades; get it wrong and you'll chase leaks forever. This pillar guide collects every Knowledge Garage article on flaring — flare types, tool selection, and technique — so you can go from first flare to factory-quality results.
Know your flare types
Before touching a tool, you need to know which flare your vehicle uses. Bubble Flare vs. Double Flare explains the two most common styles, how to identify them, and why they are not interchangeable — the single most important fact in brake line work.
Choose your flaring tool
Tool choice determines how easy (or miserable) flaring is. Fittings with Flare: A Guide to the Universal Hydraulic Flaring Tool covers the hydraulic tool that makes on-vehicle flares nearly effortless. Shop the full range of brake line flaring tools to match your budget and workflow.
Master the technique
How Do You Flare a Brake Line Easily is the step-by-step walkthrough: cut square, deburr, chamfer, lubricate, and form. Working with copper-nickel? Flaring and Forming Copper-Nickel Brake Lines shows why NiCopp is the friendliest material to flare and how to bend it cleanly by hand.
Prep your tubing
A perfect flare starts with straight tubing. If you work from coils, the Adjustable Handheld Tubing Straightener takes the fight out of coiled line and gives you a true, straight section to flare.
Shop the tools
Browse our brake line flaring tools collection — from handheld double-flare tools to the universal hydraulic set.
Frequently Asked Questions
What is the difference between a double flare and a bubble flare?
A double flare (SAE inverted, 45 degrees) folds the tubing wall over twice for a reinforced seat; a bubble flare (DIN/ISO) is a rounded single-stage form used on many European and Asian vehicles. They are not interchangeable - always match what your vehicle uses.
Can I use a single flare on a brake line?
No. Single flares can crack and leak under hydraulic brake pressure and are not safe for brake systems. Always use a double or bubble flare as the vehicle specifies.
How do I know which flare my vehicle uses?
Most domestic vehicles use SAE double flares, while many European and Asian vehicles use DIN bubble flares. Compare an existing fitting on the vehicle or check the service manual before you buy line or fittings.
Why do my flares keep leaking?
The usual causes are a cut that isn't square, a missed deburring step, or forming the flare dry. Cut square, deburr inside and out, add a drop of oil to the die, and seat the flare firmly.
Related guides
Continue with our Brake Line Replacement Guide, Brake Line Fittings & Sizing Guide, and Brake Line Materials & Corrosion Guide.