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Wed Sep 23, 2020 6:42 am

I have a '71 Super Beetle that needs its master cylinder changed out. As of right now, the brakes are drum brakes but at some point i would like to change them out for disc brakes, only for the front. Here are my questions..

1. Are the master cylinders the same for drum and disc?
2. If they are different, can you use a master cylinder for disc brakes, for drum brakes?

any additional advise would be great.

Thank you

Wed Sep 23, 2020 6:59 am

Brake master cylinder hints
Hints (first get a repair manual):
1. Use a baster or similar to pull brake fluid out of the reservoir before starting.
2. Use an 11mm flare wrench for initial loosening and final tightening of the nuts on the brake lines.
3. Pull brake lines back GENTLY, don't bend.
4. Leave mounting bolts in place in the pan when loosening (socket and extension), so the spacers don't fall in and get lost forever. see new spacers at https://www.bughaus.com/Beetle_Master_Cylinders_and_Wheel_Cylinders.htm
5. Bench bleed the new MC before installing; yeah, some fluid will drip out, enough will stay in.
6. Thread in the line nuts before mounting the MC, so there's a little wiggle room to thread them in several turns, by hand.
7. Have a helper hold/maneuver the MC into position so you can get the two mounting bolts installed.
8. Use a flare wrench final tightening of the nuts on the brake lines.
9. Adjust brakes manually with a screwdriver, all four wheels.
10. Bleed all four wheel cylinders.

Wed Sep 23, 2020 8:54 am

Izzylxiii wrote: I have a '71 Super Beetle that needs its master cylinder changed out. As of right now, the brakes are drum brakes but at some point i would like to change them out for disc brakes, only for the front. Here are my questions..

1. Are the master cylinders the same for drum and disc?
2. If they are different, can you use a master cylinder for disc brakes, for drum brakes?

any additional advise would be great.

Thank you

You can use the same.

Wed Sep 23, 2020 12:33 pm

You can safely use the stock master cylinder for a rear drum/front disc setup. But do yourself a favor: spend the extra money on a good German mc. Wolfsburg West sells a nice ATE master. I’ve had one of those in my front disc/rear drum bug for seven years with no issues.

I’ve heard too many horror stories about owners using cheap mc’s, where they were bad right out of the box. Spending the extra on this critical part of the brake system will save you having to do the job more than once, as well as money in the long run.

Tim