Between working on my and my girlfriend's bikes, I've come across different style compression ferrules (aka sleeves/olives) used in the hydraulic brake systems and would like to know:
- What is the purpose of the grove in the middle?
- Would it be safe to use a standard brass hydraulic ferrule (straight or curved body) as long as it's rated for similar or higher pressure? (I would continue to use a barbed insert rather than switch to smooth.)
To be clear, these ferrules and inserts go over/inside single or dual-layered PVC tubing.