Sorry, no tech this time, I’m talking mountain bike brakes. This is more a note to myself, but as I’ve not found this advice anywhere I’ll share it.
Shortening the lines on Marta brakes (SL in my case) is very easy, but there is one small gotcha you should be aware of.
The system is simple: the olive is pressed in place by the threaded nut and seals the connection to the lever. This is what you want to achieve (sorry for the really crappy drawing):
The problem is that it’s easy to end up in the second situation, i.e. the olive not being completely over the hose.
If you install the hose that way, as soon as you pull the lever the connection will leak oil (and suck in air). It’s not a big issue but you’ll have to correct the situation with a new insert/olive and bleed the system.
The good news is that it’s very simple to avoid this. Just keep the hose pressed all the way towards the lever with your hand while you thread the nut the first time. This forces the olive to slide all the way over the hose.
Random tips: 1) keep some margin when shortening the hose just in case you’ll have to press in another insert. 2) Make sure to have an extra insert and olive before starting, it sucks to be stuck in the middle of the process without parts.
My experience with hydraulic disc brakes is still limited, so please forgive me if all this was obvious.