Converting to dual reservoir brake master cylinder

[moore_rb]

in my limited experience, pedal feel and travel are hugely dependent on master cylinder bore...

yes, because changing bore diameter changes volume within the system - however, if you doubled the bore, and halved the ratio of the MC, you can be assured that it would feel the same.

the stock patrol has a 1 inch bore and a 1:1 ratio (one inch bore, one inch stroke)

The wilwood MC I linked above has a 1:1.1 ratio (50/50 volume output), so it moves the same cross sectional fluid volume a 10% longer distance - which means it will feel just a TAD softer.

The Corvette MC I linked to above has a 1:1 ratio (also biased 50/50) so it should feel darn near identical to a stock Patrol MC

Here is a nice image that shows the interior workings of a 2 reservoir MC- note there are 2 pistons and two return springs , and the pedal activates them BOTH simultaneously:

[moore_rb]

Just a quick update on this topic- I decided which Master Cylinder I am going to use on my green Patrol:

This is a dual reservoir, dual circuit, one inch bore MC originally for a 1967 Chevrolet C10 pickup 4x2, with 4 wheel drums and built in 50/50 bias - $26 at the neighborhood O'Reiley Auto Parts Store:



Based on my research, this one should offer nearly identical braking power and pedal feel to the stock Patrol MC, but with the benefit of isolated front/rear circuits...

Nothing left to do but fab up an adaptor for the bolt pattern, hook it up, and see if I'm right...

[faux40]

Howdy All,

After my post earlier in this thread where I made some big mistakes, I wanted to figure out and understand the whole brake thing myself. In order to do this, I chose to write a paper on brakes. It turned out a bit on the long side (which fits with the honor of "most longwinded" that moore_rb has bestowed on me! ), but with any luck, it works its way through some basic hydraulic calculations and how they work in context of brakes. Anyway, you can download the pdf here (http://balestrini.net/images/patrol_brakes_an_analysis.pdf) if you want to read it in long form. And, just to be convenient, here it is in images.

I hope you like it (and maybe it's useful!)

John

[RiverPatrol]

Outstanding! Thank all of you - John, Esteban and Chris for all of the research and effort that went into this. I'll admit I only skimmed it for now, but I have yet to see anything this comprehensive regarding the Patrol braking system.

[moore_rb]

Very awesome writeup...!

And, I can say that I learned something - I was ready to jump on the fact that US Patrols have 1 inch rear wheel cylinders, and that the entire system is "square" ; but then I saw that the 1-1/8 rear cylinders are for MWB Patrols - interesting little factoid.

The dual reservoir cylinder in my post above is perfect for anyone who wants to convert their Patrol to a dual reservoir, but wants to maintain non-power brakes. I'll be adding my "How to" steps to this thread as soon as I make the conversion on my Patrol (it will probably be a couple more weeks)

I also just noticed I did not post the part number- it is a Cardone BHH 10-1329...

[Flaggoni]

I like the schematic depiction (page 8?) of the "slave" master cylinder being in series. It made what Esteban tried to tell me about why the pedal pressure and travel wouldn't change finally soak in. I submit.
Mild Bill

[bosque]

Somebody ate my brains and I cannot compute this.....good thing the stock system is working good enough....
Nice work guys ....beyond good enough!!!

[faux40]

Just a quick update on this topic- I decided which Master Cylinder I am going to use on my green Patrol:

This is a dual reservoir, dual circuit, one inch bore MC originally for a 1967 Chevrolet C10 pickup 4x2, with 4 wheel drums and built in 50/50 bias - $26 at the neighborhood O'Reiley Auto Parts Store:



Based on my research, this one should offer nearly identical braking power and pedal feel to the stock Patrol MC, but with the benefit of isolated front/rear circuits...

Nothing left to do but fab up an adaptor for the bolt pattern, hook it up, and see if I'm right...

Hey Rob -- Any progress on the dual master cylinder replacement?

John

[moore_rb]

No, I've been slackin... Work has been kicking my butt lately... Haven't had much garage time.

Hmmmm maybe this Saturday- the schedule looks clear so far, and I'm sure the kids will be sleeping in late due to their "day after Halloween" sugar-induced insulin comas...

[XploreNV]

I was thinking about doing this as well since my brake system needs an overhauling but now my head is spinning from reading all of this.