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Author: Subject: Sierra brake master cylinder
westf27

posted on 3/8/20 at 04:48 PM Reply With Quote
Sierra brake master cylinder

Should the pushrod be inline with the cylinder or is a slight angle ok.
Changed the cylinder because it leaked.Took car for test and this one leaks.





555

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nick205

posted on 3/8/20 at 05:13 PM Reply With Quote
IIRC the brake pedal is supposed to have a 5:1 ratio.

So you take the length of the brake pedal lever between its pivot point and where your foot presses on it, divide that length by 6 then have the pivot point of the push-rod 1/5th of the way from the pivot point of the brake pedal lever. That should give you sufficient mechanical advantage when braking. Especially as most kit cars don't have servos.

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westf27

posted on 3/8/20 at 05:57 PM Reply With Quote
Thanks Nick can check that.The old cylinder and it's replacement both leak fluid from the pushed in the footwell.
Was wondering if it's because the pushed angles up slightly towards cylinder.





555

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theconrodkid

posted on 3/8/20 at 06:25 PM Reply With Quote
the rod pushes into the middle of the piston, it has no bearing on wether the cylinder leaks or not, if it leaks it need repair or replace





who cares who wins
pass the pork pies

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steve m

posted on 3/8/20 at 06:51 PM Reply With Quote
Exactly as my m8 Conrod has said.

on my original set up, I must of been about 15% off center, with no problems





Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at




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nick205

posted on 4/8/20 at 07:42 AM Reply With Quote
Photo below how I built my Sierra based MK Indy. The brake pedal push-rod isn't horizontal, but measured on the 5:1 ratio I describe above. The end of the push-rod is rounded so it doesn't bind in the master cylinder. Nver had any issues with it. The master cylinder was new at the time the car was built and never leaked. IMHO (as mentioned) if the master cylinder is leaking then the master cylinder is at fault with failed seal(s).


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