Dual Circuit Master Cylinder conversion

[Eric&Barb]

[Thompson2]

[DonVWMiller]

I did this conversion over the past month or so for my early ‘67 which had a single circuit. And replaced it with the “ATE” branded German made dual circuit from WW. I used this forum, the Bentley manual & the Idiot Book.

I did everything from the pedal bolt, the hard & soft lines, grommets, clips, Wheel cylinders - everything EXCEPT adjusters (more on that and a warning below) .... I had the shoes arced. I borrowed a Motive brand power bleeder that worked great and owe that friend some home made sweet pickles! It took me 40-60 hours and I got tube benders from Harbor Freight to fit the hard lines. The trickiest line is the one for the front brakes from the MC to the “T” as I had no pattern. I got all parts from WW and I did not use a spacer or modified push rod but will have to cut the belly pan at the rear end of the MC to fit.

The last thing to do is adjust the brakes (then bleed). As I mentioned, I used the old cleaned up adjusters. One on the rear was stuck & I had to pull the drum and work it to free it. Then I got to the front. Left front no problem. Right front top adjuster was stuck! Removed drum & bearings. Put back together and after a few adjustments (following the instructions in the Idiot Book which says “you always pry away from the tire to tighten the shoe to the drum.”

...I want to report to this forum that the “Idiot Book” is wrong!!!!

I know this sounds like blasphemy but the specific error is in the 19th edition (2001) page 170, 2nd paragraph, last sentence. In reality, for the top wheel cylinder the adjustment requires me to move the screwdriver toward the tire. I spent a couple hours messing around on this certain the Idiot Book could never be wrong. I found videos on YouTube showing me the correct way to adjust the right front top WC and was put test driving yesterday for the first time in a couple months! It sure feels nice to have & trust my brakes!

[sgellis]

Read though here but a little uncertain.

I have a 64 kombi with stock drums that I want to switch to dual circuit. Planning to get a 67 MC.

I was looking at this one but question if it is correct for drums. Did they come stock 22.2mm in 67? I don't want to make my pedal harder than it is now.
https://iapperformance.com/product/brakes/brake-hy...2-2mm.html
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My 64 Kombi restoration
My camper interior build
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The Nova Scotian Barndoor (YouTube)
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[Eric&Barb]

1964-67 used same wheel cylinders. 1955- early 64 used same size bore of wheel cylinders, but have different offset due to narrower brake shoes used.
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In Stereo, Where Available!

[sgellis]

[Eric&Barb]

[Eric&Barb]

Left click on those pages once and each will open up in its own screen. Left click on that, it will blow up nice and big to be easy to read.
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In Stereo, Where Available!

[sgellis]

[Eric&Barb]

[langsmer]

So just to be clear, the ISP West kit with the 22.2 mm bore will work fine on a 67 and earlier bus with stock drums all around?

[Eric&Barb]

[langsmer]

I figured that was the answer, but its always best to be certain when messing around with the thing that keeps you from driving into a tree. Thanks!

[sled]

this is not necessarily true, it all depends on the diameter of the disc piston(s). a smaller bore "drum brake" master will require slightly more pedal travel with a larger disc brake caliper, but the pedal will require less force.

if a disc caliper has a piston(s) with the same surface area as a drum wheel cylinder(s) then it will require the same amount of CC's of fluid.


I am running a '67 master (22mm bore) with disc brakes and it works wonderfully. The pedal travels slightly farther than with drums, but requires much less force to stop the bus. This is a function of fluid force, but also the fact that discs inherently stop better than drums.
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drive your split.

[FreddyWanKenobi]

Is anyone running the ISP WEST MC conversation? Ended up with the Empi front brake conversion but it came with a single MC. So was looking for something to upgrade too.

[Alan Brase]

As fitted to 1971 up type 2's, all used a rear pressure regulator that was also sited to sense deceleration and restrict pressure to the rear brakes under severe braking.
It might be a very good idea to add this. To keep from locking up the rears.
I would think it would not be hard to add such a device. Finding one new would be expensive, but they seldom fail and probably can be disassembled and cleaned. Setup and adjustment is detailed in the bay window Bentley. (No doubt in the orange Volkswagenwerke manual as well.)
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Al Brase
Projects: 67 sunroof bug, 67 Porsche 912 Targa, 70 Westy
Dec 1955 Single Cab pickup WANT 15" BUS RIMS dated 8/55, thru 12/55
To New owners: 1969 doublecab, 1971 Dormobile
Vanagons:
80 P27 Westy JUL 1979, 3rd oldest known US
83 1.6TD Vanagon, 87 Wolfie Westy daily driver, swap meet home

[BarryL]

Here's a version of ^^^^ that.

Here's a cross section of the inertia valve anti-lock rear brake device. They are installed on Austin Americas as well as other Lockheed systems.

From Austin America Bentley Manual: "An inertia valve is mounted on crossmember and is designed to prevent the possibility of rear wheel skidding. A steel ball inside body of valve holds open the valve allowing fluid passage. Under hard braking weight transfer causes ball to move and valve to close. A mechanical transfer causes ball to move and valve to close."

[TheVintageVw]

apologize in advance if this has been covered....

59 single cab, upgrading to an OEM 67 dual master. Will I need a new push rod or will the one off the car now work?

Thank you

[Eric&Barb]

[bobrk]