BN6 brakes not working properly

[BN6_2197]

Gents,

I changed the wheel cylinders of my front brakes since one of them was damaged. After reassembling the brake system I renewed the brake fluid and bleeded the brakes. After all that done I have the problem that on the first hit of the break pedal I have nearly no breaking power. The subsequent hits work fine. I bleeded the system several times myself. Also let it check from a friend. From my point of view it is very unlikely that there is still air in the system. Any other idea what to check? By the way I also bleeded the clutch. This works fine.

Volker

 

[John Turney]

It sounds like the brake shoes may be retracting too much. Have you adjusted them? Are the drums round, or do they drag and release as the drums are turned?

 

[BN6_2197]

John, I adjusted the shoes by fastening them until the drum does not turn anymore and then releasing them a little bit. While turning the drums the shoes drag and release a little bit. that's true. But why could that explain that only the first hit on the break pedal results in less breaking power? Volker

 

[John Turney]

If the shoes retract too far, the first hit on the brake pedal doesn't bring the shoes into full contact with the drum. If the drum isn't round and concentric with the brake shoes, they have to be backed off too far when adjusting.

 

[BN6_2197]

If the shoes retract too far, the first hit on the brake pedal doesn't bring the shoes into full contact with the drum. If the drum isn't round and concentric with the brake shoes, they have to be backed off too far when adjusting.

John, please apologize that I ask why the second hit does not have the same effect of less breaking power but results in full power?

 

[rjc157]

Have you ever replaced the hoses

 

[British_Recovery]

With two wheel cylinders, is it possible to have them positioned with the bleeder at the bottom instead of the top?
Bob

 

[Keoke]

I ask why the second hit does not have the same effect of less breaking power but results in full power?

Because:

"The first hit on the brake pedal doesn't bring the shoes into full contact with the drum". But reduces the spacing between the shoes and the drum so the second hit closes the remaining space and exerts full power in the system

 

[steveg]

With two wheel cylinders, is it possible to have them positioned with the bleeder at the bottom instead of the top?
Bob

The cylinder orientation is front and back, rather than top and bottom. With the asymmetric bolt holes in the backing plate, the positions of the interchangeable cylinders and length of the brake hose, the cylinder with the bleeder screw will always be uppermost.

 

[steveg]

Gents,

I changed the wheel cylinders of my front brakes since one of them was damaged. After reassembling the brake system I renewed the brake fluid and bleeded the brakes. After all that done I have the problem that on the first hit of the break pedal I have nearly no breaking power. The subsequent hits work fine. I bleeded the system several times myself. Also let it check from a friend. From my point of view it is very unlikely that there is still air in the system. Any other idea what to check? By the way I also bleeded the clutch. This works fine.

Volker

Sounds like you still have air in the system.

The bleeding order is: left rear, right rear, left front, right front - did you fully bleed the brakes in that order?

I've found that wrapping the bleeder screws with a couple or three layers of teflon tape and attaching the bleed hose with a hose clamp or zip tie prevents air from entering the bleed hose from the bleeder screw. You can also pack grease around where the bleeder screw meets the body of the cylinder.