View Full Version : Brakes: Master Cylinder Piston ???

09-06-2011, 02:19 PM
I read this some where but am a little confused. Does a larger piston in a master cylinder give you more pressure or less pressure? The one I have for the Parkview is 7/8s of a inch. Should I go bigger or smaller. No power brakes but disc on the front with #2 residual on front and #10 on the back

09-06-2011, 04:59 PM
All other things being equal, usually a Larger Piston creates LESS pressure.

What I never understood though is; why then does a 1/2 Ton Truck get a 1 in. a 3/4 Ton a 1 1/8 in. and a 1 Ton a 1 1/4 in. since each has progressively more weight, load capacity AND larger Brakes? :confused:

The manufacturer of your Disc. Brake Kit should be able to tell you what M/C to use.

OUR Disc. Brake Kit guy Jim Turner, can always tell you what to use on HIS kits. :)

09-06-2011, 05:35 PM
Physics: fluid flow at a given rate decreases in pressure with an increase of 'diameter' and increases in pressure with a decrease of 'diameter'.

09-06-2011, 06:15 PM
Thanks I will try to find one with a smaller piston.

09-06-2011, 06:53 PM
If you decrease the diameter of the piston ,your stroke will increase.
How are you using this?
Disk brakes , drum brakes.
Why do you want more pressure?
Are you using the newly made shoes with the very hard lining and
can barely stop the car?
Robert Kapteyn

09-06-2011, 07:03 PM
The shoes are probably hard you can't get good shoes any more. Disk drum. I am in the process of building the car now. A little at a time. It was nice talking to you at Ames, Iowa.

52 Ragtop
09-06-2011, 10:18 PM
smaller piston, more pressure, longer stroke, larger piston less pressure, shorter stroke.


09-06-2011, 10:52 PM
Just make sure you are displacing the same amount of fluid if you change sizes. Some times going to a smaller bore will also net you less total fluid and you will not be able to get the full amount of fluid you need to fully move the fluid in the caliper piston bore and the drum's wheel cylinders to give full brake component travel even at the new higher pressure. Just a cautionary note.