Some brake line tech from today. Maybe this is common knowledge, but took me some time to figure it out and is weird.
I bought stainless steel brake lines from SOR. For the axles to frame rail line, I could not tell which one was front and which was rear. They were almost the same length, but one of them had longer male threads than the other (for the axle T bracket axle side):
The caliper to axle lines both sealed with a copper washer. So I thought these would be the same. What I discovered was the front does not seal with a copper washer, but the rear one does. The T bracket for the front has a different type of connection than the rear one. If you look inside the fittings, you can see a cone shape protruding out on the front bracket, but not on the rear bracket. Pictures -
Front bracket - look inside and you can see the cone shape:
Rear bracket - look inside and it is flat...no cone shape:
So for the rear, you need to seal with a copper washer. For the front, it seals on the inside - the cone shape fits into the reverse cone shape on the brake line. It does not tighten up all the way like the rear.
Front:
Rear:
I have no idea why they are different. Seems strange and confusing.