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Gunslinger
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Another Brake question
03/10/18 at 12:39:22
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Today I pulled my drums off to start the investigation process on my brakes.  I did rebuild this system from the pedals down when I originally did the Resto, but they have been acting up lately.  The front left brake will activate prior to the others, thus a hard pull to the left, and generally they are slow to respond- hence the other topic on upgrades.

But here is today's question:  I have the drums off on all 4 wheels and had my lovely assistant (we'll call her Vana) push the brake pedal so I could watch the activation, both of the rear brakes activated prior to the front ones activating, and the front (both sides) did not move until the pedal was near the floor. 

First off, is this a valid test?  Without the drums to provide pushback on the brakes will the system activate the brake that is easiest?

Should all of the wheel cylinders move at the same time?

Ideas?
  

Climbs trees, hides in the long grass, hangs out with wet dogs...
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elawson
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Re: Another Brake question
Reply #1 - 03/11/18 at 13:47:58
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An engineer's idle thoughts here...

When the brake fluid is not moving (or not moving much), the fluid pressure at all points inside the brake system will be the same.

So, in a single master cylinder brake system, the brake with the least amount of resistance will move first.  As the shoes move outward, the return spring on that brake stretches and gets harder to move.  When the happens, the brake system pressure begins to rise..  Once the pressure rises enough, the next weakest spring will "give" and allow that set of brake shoes to move...and so on...


Since the Jeep pulls to the left when braking, I'd check the right front wheel's brake stuff first and then the right rear wheel brake.
  
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oldtime
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Re: Another Brake question
Reply #2 - 03/11/18 at 14:30:19
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A couple things can cause the brakes to pul to one side.
The fluid flow may be partly obstructed (particulate debris) inside the tubing of whatever wheels cylinders that are slow to react.
Brake fluid supply tubes can be reamed out.
Run a piano wire through the tubes and then pull a pipe cleaner through the tubes.

If old certain wheel cylinders may become rough or stuck inside.
Caused from rust or other accumulations inside the  cylinders.

The brake shoes them selves can cause a side pull if they are not all properly adjusted.

Finally the condition of the drum lining may effect a side pull.

  
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