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Bedford MW brake master cilinder

Danny P

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Just to be sure! I've dismounted the brake master cilinder from my Bedford MW for reconditioning and refilled it with brake fluid.

Then I've tested it by pushing in the cilinder at the push rod side of course. I noticed that brake fluid first came from the outlet for the rear brakes, then with some delay, brake fluid came from the outlet for the front brakes. I also noticed that more fluid flows from the rear brakes outlet than from the front brakes outlet. Is this correct?

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Thanks Louis,


Because of my curiosity I've tried to figure out how the brake master cylinder works. As you can see on the picture below there are two brake fluid reservoirs with two different volumes. No.4 for the front brakes, no.8 for the rear brakes. When the push rod is pressed in brake fluid is first taken from reservoir no.8, then taken from no.4.

Consequently more fluid will be needed for the rear brakes and therefore reseroir no.8 is arger than reservoir no.4.


So, in detail, when the push rod is pressed in the primary piston no.9 will build up pressure in primary cylinder no.6; fluid will come out for the rear brakes. Subsequently when the pressure in the primary cylinder is high enough the secondary piston no.5 will move forward and pressure will be built up in secondary cylinder no.2; fluid will come out for the front brakes.


Does anybody agree with my theory? The question that remains: is more fluid going to the rear brakes because of the distance to build up the same pressure as the front brakes?


brake master cylinder.jpg


It's better to know that you understand than to do what you think you know!:D

Edited by Danny P
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As with all commercial vehicles, the load on the rear axle when the vehicle is loaded is far greater than that on the front axle therefore the breaking effort on the rear axle needs to be far greater than on the front axle, hence the greater pressure in the rear brake line and the larger shoes. This is the opposite of modern cars where up to 90% of the breaking effort can be on the front axle.

Edited by Roof Over Britain
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