Originally Posted by andrewwynn

Experience. Old steel line almost always has more rust than you think.

I have had some success spkicing into old line but it's too risky if I can get to the ends of the full line I will always replace the whole line.

I did both my rear e53 lines with nicop and it was a breeze to clone the old "made of rust" steel lines by putting the old line in the 1/4" slot of the bender and the new line in the 3/16 slot. Taping the new to the old as I went. Made a perfect copy.

It's also at least 4x as difficult to make the flare on steel and that's actually the biggest problem on old lines. About 30-50% of the time the steel would split at the flare because it lost ductility.

It's a little tricky getting the full line out and in you have to temporarily add and subtract an extra bend if your axle is installed but totally doable.

The union to the right rear wheel is basically impossible to access without a crow foot socket but 4/10 difficulty with one (or Two: one to hold the back side).

I think I did a write up when I did mine but may have just posted on somebody else's thread