This page covers fitting, brake bleeding, what size nipples you need to buy and where you can get them.

What Is A Check Valve Bleed Nipple (CVBN)?

Starting from the end and working back. A bleed nipple is a hollow bolt that screws into the brake caliper.
This can be loosened in order to purge air from the brake system and also to refresh the brake fluid.

A check valve is a mechanical device usually made from a ball bearing and a spring. These valves allow
the flow of fluid and air in 1 direction but does not allow anything to flow in the other direction.
The fluid or air pushes the ball bearing which moves out of the way allowing it to pass.
If a force occurs in the opposite direction, the ball bearing is held in place with the spring.

As the ball bearing is remained fully seated by the pressure of the spring, nothing can pass it.

How Does This Help?

Normally, bleeding the brakes is a 2 person job or requires specific workshop equipment.
With a CVBN, it is an easy 1 person job. You just have to loosen the nipple by a quarter turn,
fit a pipe into a container and pump the brakes a few times before tightening it up again.

Fitting a CVBN

On the left is the standard bleed nipple (yours may not look as shit).
On the right is the new check valve bleed nipple in all of its shiny glory.



Before attempting to remove a bleed nipple, make sure you have new brake fluid to top the tank up.
Also, it is a good idea to soak them in penetrating fluid the day before to aid removal.
They are only small bolts and they are situated in a bad place for corrosion. Bleed nipples can easily shear off.

Clean around the nipple with a wire brush before removal then using an 8mm ring spanner, remove the nipple.