BMW Brake lines

[m996tt]

Hi can anyone tell me the what size tubing I need for
the brake lines for a BM e60

[bgunn]

4.75mm is fitted from the factory, but you can use 3/16" tubing as it's only 0.01mm larger, and you're almost certain to be replacing with copper or cunifer. Why are you replacing, out of interest?

[m996tt]

I am replacing my rear brake lines, the offside one has rusted
through, it failed about 8 miles from home. I managed to limp
home using the handbrake was at night and the roads were empty.

I have taken both sides off the car as I thought it was better to
replace them both, the rusted one fell apart as I removed it, I am
going to replace them with copper as it is quite a torturous route
the way they are fitted and didn't fancy bending the steel ones that bm
use

[bgunn]

Use 3/16" (commonly available) Cunifer pipe, with a good flaring tool. Fit the pipes into the factory locations and you'll be fine.

When you tighten up the flares, you might want to tighten/loosen/tighten a couple of times to 'seat' the flare and ensure a good seal. A small amount of brake fluid to help lubricate the fitting as you tighten will help.