Master cylinder pressure question..

Eman · 07-18-2024, 12:00 PM

Other discussion about MC's and the mention of a MC with 60/40 bias.
Someone explain to me how the MC can have 60/40 bias when the bore in the MC is the same size for both pistons/ports.
I know GM used some step bore MC's where the pistons are different sizes for each port which makes sense using hydraulic principles where the same pressure is applied to 2 different size pistons results in different pressure out of the ports.

pmrphil · 07-18-2024, 01:14 PM

The positioning of the "cups" are staggered, which changes the timing of the application of pressure

Eman · 07-19-2024, 11:35 AM

Quote:

Originally Posted by pmrphil

The positioning of the "cups" are staggered, which changes the timing of the application of pressure

Might delay application but it sounds like many think the pressures are different, including the tech guy at the company that sells them.

pmrphil · 07-19-2024, 12:03 PM

They will be different, due to the compression on one side versus the other - start compressing later would result in lower pressure.

1320racer · 07-19-2024, 12:08 PM

Pressure can only be increased by changing the pedal ratio or by decreasing the master cylinder bore.

James Packer · 07-22-2024, 10:23 PM

The bias is likely volume not pressure.

Eman · 07-23-2024, 12:03 PM

How does it put more volume to one port? Same bore size operated by the same pedal stroke.

L78 Nova · 07-24-2024, 09:09 AM

The piston is elongated with a chamber in the middle section. The forward chamber is pressurized by the front of the piston, full bore diameter.

The middle chamber is also pressurized but has reduced area due to the middle diameter of the piston carrying across to the forward piston. At any given pedal force, reduced pressure is generated in the rear chamber.

07-18-2024, 12:00 PM	#1
Eman Member Join Date: May 2014 Location: E TN Posts: 467 Likes: 16 Liked 133 Times in 76 Posts	Master cylinder pressure question.. Other discussion about MC's and the mention of a MC with 60/40 bias. Someone explain to me how the MC can have 60/40 bias when the bore in the MC is the same size for both pistons/ports. I know GM used some step bore MC's where the pistons are different sizes for each port which makes sense using hydraulic principles where the same pressure is applied to 2 different size pistons results in different pressure out of the ports.

07-18-2024, 01:14 PM	#2
pmrphil Member Join Date: Aug 2010 Location: CT Posts: 454 Likes: 1,760 Liked 345 Times in 149 Posts	Re: Master cylinder pressure question.. The positioning of the "cups" are staggered, which changes the timing of the application of pressure __________________ Phil Molski PMR Performance S/C 1623

07-19-2024, 12:03 PM	#4
pmrphil Member Join Date: Aug 2010 Location: CT Posts: 454 Likes: 1,760 Liked 345 Times in 149 Posts	Re: Master cylinder pressure question.. They will be different, due to the compression on one side versus the other - start compressing later would result in lower pressure. __________________ Phil Molski PMR Performance S/C 1623

07-19-2024, 12:08 PM	#5
1320racer VIP Member Join Date: Nov 2007 Location: New Jersey Posts: 2,628 Likes: 160 Liked 759 Times in 379 Posts	Re: Master cylinder pressure question.. Pressure can only be increased by changing the pedal ratio or by decreasing the master cylinder bore.

07-22-2024, 10:23 PM	#6
James Packer Junior Member Join Date: Feb 2013 Location: Pasco, Wa. Posts: 15 Likes: 0 Liked 3 Times in 2 Posts	Re: Master cylinder pressure question.. The bias is likely volume not pressure.

07-23-2024, 12:03 PM	#7
Eman Member Join Date: May 2014 Location: E TN Posts: 467 Likes: 16 Liked 133 Times in 76 Posts	Re: Master cylinder pressure question.. How does it put more volume to one port? Same bore size operated by the same pedal stroke.

07-24-2024, 09:09 AM	#8
L78 Nova Junior Member Join Date: Dec 2009 Location: Winnipeg, MB Posts: 92 Likes: 245 Liked 23 Times in 13 Posts	Re: Master cylinder pressure question.. The piston is elongated with a chamber in the middle section. The forward chamber is pressurized by the front of the piston, full bore diameter. The middle chamber is also pressurized but has reduced area due to the middle diameter of the piston carrying across to the forward piston. At any given pedal force, reduced pressure is generated in the rear chamber.