datmbn
forum member
The need is the mother of inventions !
A while ago when I helped a person to change a brake tube, a bleeding nipple
couldn't get loose, and then I started to think about whether there was any other way to get the air out?
I then found that the volume of liquid present in a fully pumped brake piston is quite large, probably larger than the volume in
the brake pipe!
OK little count the inner diameter of a "normal brake pipe is 2.8 mm cross area then becomes 1.4x1.4x3.14 = 6.1
The diameter of the brake pistons on the eg Mustang is 60 mm front and 38 mm rear with a stroke length of 50 and 40 mm, respectively.
The volume of liquid then becomes 30x30x3.14x50 = 141300 and 19x19x3.14x40 = 45341, respectively, if we then divide these volumes with the cross-section of the pipe
we get the pipe length corresponding to the volume of the piston 141300 / 6.1 = 23163 mm 45341 / 6.1 = 7432 mm
We can thus conclude that the volume of the piston more than enough is enough to fill the tube (even if we count on ABS and main cylinder)
The only thing you need to do to get the brake aired is to pump out the piston as far as possible and push it back.
let's say 2 times to be sure.
If you are unsure whether the rear volume is really sufficient, then work diagonally (two-circuit brakes)
and also use the piston forwards (pump out both pistons press back rear and then forward)
How did it work in practice? After the change of tube, the brake was perfectly aired and the car went through the inspection.
This method I will use the next time I change brake fluid
regards Mats
A while ago when I helped a person to change a brake tube, a bleeding nipple
couldn't get loose, and then I started to think about whether there was any other way to get the air out?
I then found that the volume of liquid present in a fully pumped brake piston is quite large, probably larger than the volume in
the brake pipe!
OK little count the inner diameter of a "normal brake pipe is 2.8 mm cross area then becomes 1.4x1.4x3.14 = 6.1
The diameter of the brake pistons on the eg Mustang is 60 mm front and 38 mm rear with a stroke length of 50 and 40 mm, respectively.
The volume of liquid then becomes 30x30x3.14x50 = 141300 and 19x19x3.14x40 = 45341, respectively, if we then divide these volumes with the cross-section of the pipe
we get the pipe length corresponding to the volume of the piston 141300 / 6.1 = 23163 mm 45341 / 6.1 = 7432 mm
We can thus conclude that the volume of the piston more than enough is enough to fill the tube (even if we count on ABS and main cylinder)
The only thing you need to do to get the brake aired is to pump out the piston as far as possible and push it back.
let's say 2 times to be sure.
If you are unsure whether the rear volume is really sufficient, then work diagonally (two-circuit brakes)
and also use the piston forwards (pump out both pistons press back rear and then forward)
How did it work in practice? After the change of tube, the brake was perfectly aired and the car went through the inspection.
This method I will use the next time I change brake fluid
regards Mats
