325iS hard line flare

[newolde30]

Can someone please help me figure out why the bubble flaring tool I bought won't flare the passenger front line? It is a 4.75 mm.
The tool flares just fine a short section of tubing I bought from the parts store to practice my flares with. Once I felt really comfortable with my flaring method, I tried to do it on the car and it just won't flare.
Do I need a 4mm tool?
thanks,

[BMW_TUNER]

I used a 4mm tool and you have to get it crazy tight. I practiced on some line I got from a yard. Redid my entire abs setup.