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Tech: More Brake Master Cylinder FAQs


You had questions; we had answers. And then you had more questions!

A while back, we had the Summit Racing guys answer some of your common brake master cylinder questions. In this video, they take on a few more of your questions, including:

  • Can you use a drum brake master cylinder on a disc brake system?
  • What is the proper piston bore size on a manual brake master cylinder?
  • Can you use a manual brake master cylinder to operate power brakes?

Watch now to get the answers!


Today, we are going to answer your questions about disc brake master cylinders, drum brake master cylinders as well as the differences between master cylinders for power brakes versus manual brakes. So let’s start with disc brake master cylinders versus drum brake master cylinders. Typically a disc brake system is going to require more fluid to operate properly, so a disc brake master cylinder will simply hold more fluid than a drum brake master cylinder. On a drum brake master cylinder, you will also have residual pressure valve to maintain a certain amount of pressure at all times. This is to prevent air from entering the braking system.

So can you use a drum brake master cylinder on a disc brake system? We hear that question quite often. You can, but you are going to compromise some of your braking effectiveness, and the reason is simply because once again the drum brake master cylinder holds less fluid than the disc brake master cylinder. And again, that disc brake system requires that extra fluid to operate at maximum effectiveness. Also, that residual pressure valve that we told you about on the drum brake master cylinder is going to cause a little bit of a drag on the disc brake system’s rotor and that is going to affect the overall braking ability of the system.

Another question we hear is can I use a disc or drum brake master cylinder on a four wheel disc brake system and the answer is simply, no you cannot. You are going to need to use a special master cylinder design just for the four wheel disc brake system to get the proper amount of brake fluid volume and pressure to operate the four wheel disc brake system properly.

Now we are going to talk about manual brake master cylinders and power brake master cylinders. On a manual brake master cylinder there is going to be a smaller piston bore to maintain the proper fluid pressure required to operate manual brakes. There is also a deeper hole for the brake pedal push rod. Now you can use a manual brake master cylinder to operate power brakes but not vice versa. Power brake master cylinders have a larger piston bore diameter and are not able to supply the fluid pressure required to operate a manual brake system.

Another question we get regarding manual brake master cylinders is what is the proper piston bore size or piston bore diameter. You are not going to want to go any larger than a one-inch diameter in order to maintain the proper fluid pressure to operate the manual brake system. If you have more questions regarding brake systems or any high performance related topic feel free to leave a question in the comment section below.

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  1. Raymond Rowlands says:

    Hello Dave. I have an issue. 1973 ford quadravan. Stock one ton rear axle and drum brakes. Front was converted to disc. caliper piston is 75 mm. Power brake. I can’t get a good pedal. What is your recommended master cylinder piston size. Thanks again. Love the articles. Ray

  2. I have a 1968 Camaro that I currently have manual 4 wheel drum brakes. I am going to install Front disc brakes in a year. I need to replace the master cylinder now because it is leaking. Can I install a disc brake master cylinder with my 4 wheel drum brake system for now so I don’t have to buy a drum brake MC now and a Disc brake MC in a year.

  3. Jayson Yavorsky says:

    Dave, I bought a 93 jeep wrangler, some time in the life of the jeep, the original rear drum brakes were replaced with GM C10 front brakes. The original disc/drum MC is still on the jeep and a very, very soft pedal is now current. I know I need a 4 wheel disc MC, but What bore size master cylinder should i put on. I am keeping both the original front disc brakes and the replaced GM, now rear brakes.

  4. Hello Dave, I’m a member YTU Racing Formula Student Team. Asking it what is the proper master cylinder bore size of the hydraulic clutch system?

  5. I have replaced all my brakes in my 1969 chevelle with wildwood 6 piston dynas in the front and 4 piston dynas in the rear I have a 1 1/8 wildwood master cly on the factory vacuum booster and the pedal travel goes near the floor before I get some brakes at the frt wheels I have bled the master cly according to wildwood instruction and have had no success. With the ordinal master in place I get brakes frt and back but not nearly the way the should be . Please help!

    • Hey mate i did the same combo on my 68 camaro. My brakes feel ok but im still not 100% happy with how the car stops. I mucked around with the pedal ratio to give it more force. I reckon im going to install a 7/8 bore master cylinder for more pressure. Let me know what you did. Cheers

  6. i have 4 wheel dish brakes on my 72 maverick, what master cylinder do i need to use it has the manual drum master cyclinder on it now and have to reall get down on the pedal to stop. just wonder if ya had a part number or another ford vrhical that would work for my set up

    • OnAllCylinders says:

      The answer will depend on the sizes of calipers front and rear and whether the system will be power assisted. Call the Summit tech line at 1-330-630-0240 and they’ll be able to help based on your specs.

  7. Hi I have vl big brakes on front disc nine inch on rear having prb with foot travel have 15/16 master cyndiler with bosster but peddle has a lot of travel

  8. Hey i have a 97 ford f150 and my master is in the process of going bad i have to pump the brakes to stop correctly i pulled a master off of another truck looks exactly the same and fits the same other than mine says 1 1/16 and the one i pulled is 1 1/4 ive heard the diffrence is one is for disc and drum (what i have) and one is for 4 discs the question i have is can i still install the master and if i do will it work effectively

  9. Billy Hubbard says:

    I Have a 1967 Nova w/all wheel disc. I have a single diaphragm booster. My problem is poor brakes .will not lock tires

  10. Try a brake proportioning valve.

  11. Mark Patrick says:

    I am converting front manual drum brakes to disc brakes. Will the current master cylinder work?

  12. jimi brown says:

    I’m restoring a 1939 Graham Supercharger model 97. I’m staying with the 4 wheel drum brakes but the old master cylinder needs replacing. Do you have a recommendation for a modern master cylinder that would fit my application? Thanks

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