Different master brake cylinder for disc and drum brakes?

[purity]

I'm planning to install disc brakes from a 1303S on the front wheels of my 1302. I have bought used everything from the spindles out, so that should go smooth.

But I've read that I also need to use a master brake cylinder from a beetle with disc brakes, because drum brakes use a cylinder that applies a little pressure on the brakes after the pedal is let up, where disc brakes are self-adjusting and don't need this. The combination of "rest-pressure" and disc brakes is said to not work that great.

Any thoughts/experiences with this?
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- '67 1300 (Original)
- '71 1302 (Daily driver, TIV-engine going in)

[bon2198]

yes the master cylinder is different. www.cip1.com has a kit a lot of people use.
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1970 VW Beetle 1776cc MOFOCO w/hydraulic lifters, 042 heads and dual dellorto's
"It's better to be hated for what you are than loved for what you are not"

At the end of the day it's YOUR car so do what YOU want to it.

[2002sportside]

No, the master cylinder is the same. The disc brake master cylinder is a new item, released in the last few years. The Karmann Ghia had a disc/drum setup from the factory and uses the same master as a drum/drum Beetle.

A "disc brake master cylinder" is not needed. I have no issues with a stock cylinder and Ghia disc setup, and I have never read of any either. I know some owners have been running on a stocker for thousands of trouble free miles.
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1973 Volkswagen Beetle never ending project

[jbrandt01]

I believe the masters for discs had a 'v' cut into the mounting flange and the ones for drums have countersunk backsides on the mounting flange.

What exactly that implied I think had something to do with the inclusion of residual check valves. I believe the purely drum only masters had the valves on the output while the disc masters had small pressure drilled channels internally. IIRC, the ones without the residual pressure valves can be used on both disc and drum setups.

[olspeed]

What year is you SB, 1973 and later have master cylinders that have restriction drillings and MUST be changed out to make disc's work. If it's a 71 or 72 you will need to pull the residual pressure valve for the front wheels from the master cylinder. The Bentley manual states: The master cylinders for 1973 ans later models with four wheel drum brakes also have restriction drillings rather than residual pressure valves. These master cylinders must not be interchanged with those used on cars with dice brakes. To prevent confusion, the drum brake type is marked by a countersink in the mounting flange, adjacent to the boss for the supply line from the fluid reservior. Disc type cylinders are marked with a v-notch on the side of the mounting flange, near the mounting bolt hole:
Olspeed
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66- Ghia
76-Beetle

[2002sportside]

The information in the Bentley would be useful IF you could still get those two different master cylinders. Most of the vendors sell one master for '71-79 Supers, and one for '67-77 Beetles.

The "disc brake" masters available today are not the same, they have a larger bore than a standard master. They are sold with the notion that wider bore allows for better braking.

If you feel you need one, go for it.
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1973 Volkswagen Beetle never ending project

[fonzzey]

bottom line: either one will work with discs up front. both my bugs have ghia discs and drum masters, a panic stop will put your forehead on the windshield.
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74 Standard, stock
70 Vert, 2275 48 IDA, Super-Flo, Sidewinder with heat

[solar649]

Drum brakes require a higher that disk brakes. This is why when building racing brakes systems you cna buy a 2lb res press valve for disk brakes and a 10lb res pressure valve for drums. yes you can use the drum master cylinder on the disks. but like said about. slamming on the brakes may throw you hard. This will lock up the disks very quick.