Bleed nipple at master cylinder

[Doctor T]

Can someone tell me why the front master cylinder has a small bleed nipple fitted?. Can't seem to find any information regarding this.

[bicyclenut]

Can't tell you the technical reason for this, but when I replaced a brake line to fit some barbacks, it was the only way to get the air out of the brake line. I tried bleeding at the wheel cylinders multiple times and no go. Found info about using this bleeder nipple and did a typical bleed procedure a couple times and the air was gone. Must allow for bleeding when the master cylinder is empty or replaced. All I can say if if you are having problems bleeding the lines at the wheel cylinders, use this as a final step and it works. When I did a normal fluid replacement and brake bleed last week I did not have to use it.

[Doctor T]

Make sense as the air rises to the top. Just cant remember seeing the set up before. Cheers