Hose and fittings for racing and performance builds

SizingThe mistake that costs a rebuild

The AN system was built around rigid tube, where the dash number is the nominal outside diameter in sixteenths. A -6 fitting mates to 3/8 inch tube. But a hose is not tube: it has a wall, so the actual flow path inside a -6 hose is meaningfully smaller than 3/8 inch.

It gets one step more awkward, because the bore differs between constructions. A PTFE-lined -6 and a rubber-cored -6 do not have the same internal diameter, so two hoses that take the same fittings can flow differently.

The fix is to spec the bore you need first, then find which dash size gives you it in the construction you are using. That is a conversation with whoever supplies the hose, not a chart you can memorise.

FittingsAN and JIC are not interchangeable

Both use a 37 degree flare. They will thread together. They will often even seal, on a bench, at low pressure.

They are still different specifications, with different tolerances, materials and quality requirements. AN grew out of aerospace practice and JIC out of industrial hydraulics, and the parts are manufactured to different expectations even where the geometry matches.

Mixing them is not automatically catastrophic, and plenty of builds run happily with both. What you should not do is assume they are the same part at different prices, or mix them on anything where a leak has consequences. If you have a box of fittings and cannot say which is which, that is a good reason to standardise before the build goes together.

See hydraulic fittings and adapters for the industrial side, and bring what you have if you want it identified rather than guessed at.

ConstructionWhat braided stainless is and is not

A braided stainless line is a core with a stainless outer braid over it. The braid is structural: it restrains the core so the hose does not swell under pressure, which is why braided brake lines feel firmer than rubber.

Two things follow that people underestimate.

• The braid is abrasive. It is woven wire, and it behaves like a file. Left resting against a chassis rail, a wiring loom or another line, it will wear through whatever it touches, and it will do that faster than anything else in the engine bay.
• It hides the core. You cannot inspect a braided line the way you inspect rubber. Cracking, swelling and chafing all happen under the braid where nothing shows until it leaks.

Which means routing and restraint matter more on braided lines, not less. Every point where a braided line can touch something needs a clamp, a sleeve or a rethink.

LinersPTFE versus rubber core

Choosing the core

Core	Suits	Trade-offs
PTFE	Ethanol and methanol fuels, aggressive chemicals, high temperature, low permeation	Stiffer, larger bend radius, costs more, needs the matching fitting system
Rubber core	Pump fuel, oil, general performance plumbing, tighter routing	Permeates more, and some liners are attacked by high ethanol blends

The deciding factor is usually fuel. A rubber-cored line perfectly happy on pump petrol can be degraded by a high ethanol blend, and methanol is harsher again. If the car runs E85, methanol or anything exotic, the liner needs to be rated for it rather than assumed to cope.

Permeation is the other reason people move to PTFE. Fuel vapour passes through rubber over time, which is why a garage with braided rubber fuel lines smells of fuel and one plumbed in PTFE does not.

EndsReusable or crimped

Neither is better in the abstract. Reusables suit a build that will change, where being able to shorten a line in your own garage is worth a great deal. Crimped suits a finished car, and anything where you want the joint measured rather than trusted.

One caution on reusables: assembly technique matters enormously, particularly getting the hose fully home in the socket. A reusable end assembled slightly short holds fine until it does not. More on crimped assemblies in crimping vs clamp-on.

BrakesThe claim to be careful with

We build DOT brake hose assemblies, including in braided stainless, and there is more on how the marking works in are your brake lines DOT approved.

InstallationWhere performance builds actually fail

• Support it properly. Unrestrained line moves, and moving braided line destroys whatever it touches. Clamp at sensible intervals rather than letting spans hang.
• Respect the bend radius. Published for every hose, and PTFE is considerably less tolerant than rubber. A tight bend on PTFE kinks the liner permanently.
• Check through full suspension travel. Not at ride height. Jack the car, drop it, cycle the suspension and watch what the line does at both extremes.
• Keep it away from heat, or shield it. Turbo housings and manifolds radiate hard, and a line that is fine at idle is not fine after twenty minutes on track.
• Leave slack for engine movement. The engine moves on its mounts and the body does not. A line pulled taut between them fatigues at the fitting.
• Do not use thread tape on flare fittings. A 37 degree flare seals on the cone, metal to metal. Tape there stops the faces seating and sheds into the system.

At the counterWhat we build

Performance work is a real part of what walks in, and it gets the same treatment as fleet work: correct specification, matched components, measured crimps.

• Braided stainless assemblies in PTFE and rubber core, built to length with the ends you want. See high performance hoses.
• AN fittings and adapters, including the conversions between AN and pipe thread that most builds need somewhere.
• DOT brake hose assemblies for cars that use the road. See brake, fuel and power steering.
• Silicone for coolant and charge air, where temperature rather than oil is the problem. See silicone hoses.
• Custom A/C lines for swaps and restorations where nothing off the shelf fits.
• Sleeving and clamps to stop braid destroying everything near it. See hose accessories.

Bring the old line, a drawing, or the two fittings you need joined and a length. Most assemblies are finished the same visit. More on custom hose fabrication.