Brakes - Pipe end flares

11 July 2003

One day I'm going to have to try and assess just how it is that every now and again I get a 'run' on folks asking me about a specific problem. These problems exist all year round, year in, year out. And said problems crop up throughout the year. But - every now and then there's a blood-rush on a certain issue. Just recently that issue has been brake pipe ends. The bit that seals the pipe off against it's relevant fitting.

There are two types of end - male and female. The male end is convex in shape, the female concave. The male end is used where a male pipe union (nut) is used on the brake pipe - that's a nut with an external thread - that will be screwed into a female fitting such as found in a wheel cylinder or master cylinder. The female end is used where a female pipe union (nut) is used on the brake pipe - a nut with an internal thread - and will be mated to a male fitting such as found on rear flexible brake pipes. Under no circumstances should you mix the too up as the brake pipes simply will not be properly and safely sealed off. The male convex end fits up against a concave seat in the bottom of the female fitting; the female concave end fits up against a convex seat on the end of the male fitting - both a form of 'ball and socket' type application. These are all clearly visible and recognizable to the naked eye.

It is therefore essential you double-check these fittings before attempting assembly. Just because you have bought ready-formed pipes does not automatically guarantee the correct end forms are used. Illustrated by a guy asking me about the above issue; he'd bought a ready-made pipe for the clutch master cylinder to slave cylinder flex-pipe, but it refused to seal where it went into the flexible pipe. He'd done the pipe nut up as tight as he'd dared to go, but still it leaked. On removal it was found the pipe had had a female end formed on it instead of a male end (the clutch flex pipe has a female union in the end of it where the metal pipe joins it from the master cylinder). The situation and consequences could be far worse where braking systems connections are incorrectly matched… If you have to tooling to form your own metal brake pipe ends then the male convex shape is achieved with a single or first operation (flares the pipe out and leaves the convex shape), the female concave shape by a second operation (pushes concave male shape back on itself to form the concave cup of the female shape). These two operations are generally termed 'single flare' (male/convex) and 'double flare' (female/concave).

Whilst we're on the subject of brakes, this is a good time to bleed your brake system through. With use, brake fluid degrades as it experiences the myriad of hot/cold cycles in use - worsened in the summer by higher ambient temperatures and dry roads (hopefully) that allow the 'progressive' drivers amongst us to really use the Minis grip; Especially when shod with the latest technological wonders in the tyre market - and absorbs moisture. None of this is good for efficient and effective braking. Whilst bleeding the brakes you can also take advantage to deal with the bleed nipples. Over the winter they will be subject to copious quantities of corrosion-inducing crud. If they are partially seized or tight now, they will be impossible to shift next spring! So whisk them out of the caliper/wheel cylinder at each corner (one at a time is best), clean them up with a wire brush, then smear quality anti-seize copper grease on the threads and replace. It'll save a dense cloud of blue air come spring when you attempt to undo the nipples and they shear off!