Good evening all,
Need a little advice! last year I replaced most of the brake lines on EOW 1W and on checking the pipes were bubble flared, however today I was replacing the front left and upon removal I noted that this was double flared!!!! I am assuming that bubble replaced double in the mid 80's and the male nut appears with a recess to accept a double whereas the new nuts look flat so to accept a bubble flare (hope your all following this because I am now lost) What I need to know is obviously because of the nuts a bubble flare is the way to go, but is it in any way compromising the seal of the pipes?
Terry, as Peter has said, you need to check the surface inside any connection that a brake pipe is mating with. It will either be convex or concave and the flared end of the pipe has to match it. So if a union has a concave or dished-in surface where the end of the pipe seals then the end of the pipe needs a convex flare (what you are calling a 'bubble' I think). A convex surface will need a concave flare end (what you are calling a 'double'). Most pipe end flaring tools create a convex first and then 'squash' that to create the concave end shape on a second operation (giving you that double material thickness).
Usually unions, cylinders or calipers will have a concave shape and need a convex pipe flare. The most common need for a concave pipe flare is when it connects to a flexible hose which usually has a convex end shape.
There is a third flat end but that is more rare and certainly not used on the Murena to my knowledge.