Big brake conversions, increased engine fuelling demands, and upgraded clutch systems are just a few things on modified cars that mean factory-fit rubber fluid hoses and the standard fixings may be reaching the limit of safe performance. The solution is to replace safety-dependant lines with steel braided hoses and fix them in place with AN (Airforce Navy) fixings. Not only do the braided lines take larger fluid pressures, but they will dissipate heat better, and allow for any hose to be fitted, undone and refitted multiple times with no fraying, damage or weakening of the fixing. Oh, and they look good too.
There are two basic braided hose types. These are;
n A rubber (or synthetic rubber tube) with an inner half-braid covering and full-braid outer stainless-steel layer. These have a working temperature range of between -50 degrees and +150 degrees C and are good for fuel, oil and coolant systems requiring lightweight and flexibility, together with increased heat and strength resistance.
n A Teflon tube with single-braid outer cover. The working temperature range of these is between -73 degrees and +232 degrees C, and they are suitable for braking systems and for higher pressure fuel, oil and coolant applications.
In addition to these hoses there are also twin layer synthetic hoses with a half-braid sandwiched between the layers, which are good as a first stage upgrade. And past that, there are also ultra strong and lightweight Kevlar-braided hoses for serious motorsport applications.
AN fixings come as a male and female component, which screw together to complete the joint. These come in a variety of sizes to suit the application. The male end is usually fixed to the car’s component, e.g fuel tank, turbo housing, oil reservoir or in the case of brake systems – a banjo union which attaches to the caliper and has a threaded male fixing. On either end of the braided hose will be the female end to the correct size.
Another advantage of the AN system is that the unions can be straight, angled or in extreme cases turn a hose through 180 degrees to allow the plumbing to be bespoke-routed in even the tightest areas.
Adaptor unions can also be used on the AN system which can add in extra angles to the hose line, increase or decrease the line bore, or split the line in to multiple lines via T- or Y-sections.
Most of the braided hose manufacturers supply ready-made kits for certain cars and applications and most will also make up bespoke kits to suit your car, given accurate measurements and details. The best way to make sure all is correct, however, is to DIY, measuring the length of hose required, working out the AN fixing dimension needed and putting together a kit for yourself. And here’s how…
Measure the hose length required, and mark by wrapping masking tape around the area to be cut. The best way to cut the hose is with a junior hacksaw – but don’t exert too much pressure as the ends my fray.
With the hose end securely supported you can insert the newly cut hose – using a twist-and-push motion. The hose needs to be inserted until it reaches the back of the socket threads.
Now mark the position of the hose after it’s been inserted to the hose end – we did it with masking tape. This will allow you to see if the hose is being pushed out when you assemble the hose end.
We found it helpful to use a bit of light oil inside the the hose and on the threads of the hose ends. We also used a pair of long-nose pliers to ‘open’ the hose slightly before insterting the hose end. Ensure the hose end and nipple have a liberal coating of oil to prevent snagging.
Ensuring everything is square to prevent cross-threading, gently insert the hose end into the hose until the threads engage. Hold the hose to prevent it from being pushed out as the hose end is inserted.
Tighten both halves of the hose end together – use the correct spanner to prevent damaging the hose end. Ensure there is sufficient oil on the threads as you tighten everything up. Continue to tighten the hose end until you have a gap of approximately 1mm between the two halves – for a neat finish rotate so that both ‘flats’ line up.
Before you can fit the hose it’s vital to double check that the hose has not been pushed out. If all is okay, then a quick clean up and remove the tape is all that remains to do.