Brake Line Flaring Types and Which Tool to Use
Single, double, 45 degree and ISO bubble flares explained, with the tubing sizes each fits and the kits that cut them.
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A brake line job ends at the flare. A line that looks right can still weep fluid at the fitting if the flare shape does not match the seat it seals against. Brake line flaring types are the flare shapes cut into the end of a line: a single flare, a double flare, and a bubble flare.
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Below: each flare type and the kits that cut them.
Mastercool 72475-PRC Hydraulic Brake and Fuel Line
A hydraulic kit that cuts 45 degree single and double, push connect, GM fuel line and ISO bubble flares for 3/16 to 1/2 inch and 4.75 mm to 10 mm tubing.
Pros
- 45 degree single and double, push connect, GM fuel line, ISO bubble flares
- Hydraulic ram removes manual strain
- Fits 3/16 to 1/2 inch and 4.75 mm to 10 mm tubing
- Magnetic holder and die arm keep dies in place
Cons
- No brake line or fittings stated in the listing
- Weighs 11.86 pounds, the heaviest kit in this guide
- Mini cutter fits 1/8 to 5/8 inch O.D. tubing only
- Hydraulic body and case need more room
smseace 3/16Inch+3/16Inch Brake Line Flaring Tool
A 102-piece kit with 2 lengths of 25 FT zinc-plated 3/16 inch line, a double and single flare tool, a 3-in-1 bender and a cutter.
Pros
- 102 fittings with 2 lengths of 25 FT zinc-plated line
- Double and single flare tool for 3/16 to 1/2 inch tubing
- 3-in-1 bender bends copper, aluminum, stainless steel to 180 degrees
- Cutter handles 1/8 inch to 7/8 inch (3-22mm) pipe
Cons
- No ISO bubble or push connect flare stated
- Line and fittings are 3/16 inch; larger tubing needs its own line
- No weight stated in the listing
- No storage case stated in the listing
Racewill 25 ft 3/16 Copper Coated Brake Line Kit
A 25 ft copper-coated 3/16 inch brake line kit with brass fittings and a double and single flaring tool for 3/16 to 1/2 inch O.D. tubing.
Pros
- Copper-coated steel line bends by hand and resists rust
- Double and single flares for 3/16 to 1/2 inch O.D. tubing
- Brass fittings resist rust and corrosion
- Fits hydraulic braking, fuel and transmission systems
Cons
- Title counts 16 fittings plus 4 unions, bullets call them 20 fittings
- No warranty term stated in the listing
- No bender or cutter in the kit
- Fittings are for 3/16 inch line only
Luney 26PCS 3/16" Single Brake Line Flaring Tool
A 26-piece kit with a 25FT zinc-plated 3/16 inch line, 16 brass fittings, 2 unions, 4 nuts, a bender, a flaring tool and a cutter.
Pros
- 25FT zinc-plated line with 16 brass fittings, 2 unions and 4 nuts
- Bender, single flaring tool and cutter in the box
- Brass fittings and unions for long service life in high-pressure use
- Line bends by hand or with the bender
Cons
- Single flare only; no double flare stated
- No warranty term stated in the listing
- Line and fittings are 3/16 inch only
- No tubing sizes stated for the flaring tool
Brake line flaring types: single, double and bubble flares
The listings name a single flare, a double flare and a bubble flare, plus push connect flares and GM fuel line flares from Mastercool. The Mastercool listing states its single and double flares are both 45 degree flares, while its bubble flare is an ISO bubble flare. A single flare turns the tube end outward into a cone. A double flare folds that cone back on itself, so the sealing face is a double thickness of tube wall. A bubble flare forms a rounded bubble at the tube end.
| Flare type | What the listing states | Kits that cut it |
|---|---|---|
| Single flare | Single flaring; the Luney listing states single-end flaring of soft steel tube | smseace, Racewill, Luney, Mastercool |
| Double flare | Double and single flaring | smseace, Racewill, Mastercool |
| 45 degree single and double flare | 45 degree single and double flares | Mastercool |
| ISO bubble flare | ISO bubble flares | Mastercool |
| Push connect flare | Push connect flares | Mastercool |
| GM fuel line flare | GM fuel line flares | Mastercool |
Which flare type fits which brake line
Match the flare to the fitting the line connects to, then match the tool to the tubing. The Mastercool listing states its kit fits tubing from 3/16 inch to 1/2 inch and 4.75 mm to 10 mm. The smseace and Racewill listings state their flare tools apply to 3/16, 1/4, 5/16, 3/8 and 1/2 inch tubing. The Luney kit centers on a 3/16 inch line, with no other size stated.
Racewill lists copper, aluminum, brass, magnesium and soft steel tubing for its tool. The smseace bender handles copper, aluminum and stainless steel pipe, and its lines are zinc-plated. Luney lists zinc-plated line with brass fittings, and Racewill lists a copper-coated steel line with brass fittings.
How to pick a flaring kit for the job
- Confirm the flare types. Pick a kit whose listing states the flare shapes the job needs. Only the Mastercool listing states ISO bubble, push connect and GM fuel line flares.
- Confirm the tubing size. The tool must state the tubing size the job uses.
- Count the line and fittings. The smseace kit carries 2 lengths of 25 FT line with 102 fittings, while the Mastercool listing states no line or fittings.
- Check the cutter and bender. The smseace cutter handles 1/8 inch to 7/8 inch pipe, its bender bends to 180 degrees, and the Mastercool cutter handles 1/8 inch to 5/8 inch O.D. tubing.
- Check the warranty. The smseace and Mastercool listings state a 1 Year warranty; the Racewill and Luney listings state no warranty term.
Use rated jack stands on solid ground, wear eye protection with power and air tools, keep fuel-burning equipment out of a closed garage, and follow the manual for every tool. Read our Safety Disclaimer.
A flare that leaks is a brake job undone. Brake lines carry fluid under pressure, so a flare that does not seat will weep at the fitting. Check each flare and union for leaks before the vehicle moves.
Flaring kits for brake line work
The flare type the job needs decides the kit.
FAQ: garage tools
What are the main brake line flaring types?
The listings name single flares, double flares, 45 degree single and double flares, ISO bubble flares, push connect flares and GM fuel line flares.
What is the difference between a single flare and a double flare?
A single flare turns the tube end outward into a cone. A double flare folds that cone back on itself, so the sealing face is a double thickness of tube wall. The Luney listing states single flaring only.
What size tubing do these flaring kits fit?
The Mastercool kit fits tubing from 3/16 inch to 1/2 inch and 4.75 mm to 10 mm. The smseace and Racewill flare tools apply to 3/16, 1/4, 5/16, 3/8 and 1/2 inch tubing.
Do the kits include brake line and fittings?
The smseace kit includes 2 lengths of 25 FT line with 102 fittings. The Racewill kit includes a 25 ft line with 16 fittings and 4 unions. The Luney kit includes a 25FT line with 16 fittings, 2 unions and 4 nuts.
Related: best brake line flaring kit, best double flare brake line tool, best hydraulic brake line flaring tool.
