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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

    • Wayne Deweese says:

      I had the same problem on my 40 chev coupe with Camaro suspension front and rear problem was not enough pedal stroke made a push rod from the pedal to the booster that was shaped in a z pattern and it went farther down on mu pedal arm and it fixed everything so drill a hole farther down on your peal are and experiment

  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

  13. Moises Gonzalez Ch. Jr. says:

    Hi I habe a 1966 Ford Mustang coupe already install a power brakes with a dual master cilynder for drums. Can I use the same master cilynder and install disck brakes in the front wheels?

  14. skip Earlscourt says:

    Hi dave i am restoring 1964.5 mustang coupe it has a 4 speed the brakes have a booster i want to put disc on front but cant find 1″bore duel master cylinder short enough to fit can only be 6.25″ long and low profile so it dosent hit shock towers low enough so its below bracing or narrow enough to miss bracing,any ideas.

  15. David Attard says:

    Hi mate
    David from Malta
    I have a Australia Holden
    I have a Holden kingswood hq 1971 and I have removed all the drums brakes and put all new brake master cylinder four wheel discs new discs pads master cylinder lines all parts are new
    Now I bleed the brakes 3 times no air
    Then all of a sudden the peadel go down one pump peadel go up I have a new brake master cylinder I think that the master cylinder size is to small 15/16
    Your help would be appreciated thanks David from Malta

  16. Clifford Black says:

    Hello and thanks for the explanation, BUT my question is about a 1965 Mustang with manual brakes (incl master cylinder which needs replacing) with front disc and rear drum. Is there a way (without spending $$$$$$$) to use a better, more efficient master cylinder to increase the stopping power

  17. Rick Bittle says:

    I recently installed a master cylinder/booster combo with a proportioning valve on my 56 chevy 210.I have disc brakes on the front and drum brakes on the rear. After getting the kit installed and ready to bleed it, I realized that I had accidentally ordered a disc/disc master cylider kit instead of a disc/drum kit. Will this system work on my disc/ drum car. It was quite a job, so I don’t really want to remove the kit. Could I possibly just change the proportioning valve and make it work with on my disc/drum system.

  18. Olin Cannon says:

    I recently chng my 1991gmc sierra brake on the rear from drum to disc and now my brake pedal goes almost to the floor before stopping do I need to chng my master cylinder

  19. luke Davies says:

    i have a 74 Nova single piston disc brakes on front and a set of wildwood 4 piston disc brakes on the rear with a inch wildwood master cylinder and booster up front, I changed hot rod master cylinder from 1-1/8 to wildwood 1 inch have bled brakes all-round adjusted brake pedal and still have barley any brakes on rear…..…….. what could this be please

  20. Alan Robinson says:

    Putting rear disc brakes on a 47 cadialiac, adding 10 bolt Chevy rear, car has power brakes and current master cyl is from 65 caddy. Car already had disc brakes on front. Now petal going to the floor with air bleeding done. What master cylinder would u recommend for this application??

  21. TEMO RODRIGUEZ says:


  22. Elmer Griffin says:

    I have a 1968 Camaro that currently have manual 4 wheel drum brakes. I am going to install Front disc brakes in the near future. I need to replace the master cylinder. Can I install a disc brake master cylinder with my 4 wheel drum brake system for now?

  23. Elmer Griffin says:

    I have a 1968 Camaro currently have manual 4 wheel drum brakes. I am going to install Front disc brakes in the near future. I need to replace the master cylinder now. Can I install a disc brake master cylinder with my 4 wheel drum brake system?

  24. Just converted my 1966 American Rambler the front to disc brake and the rear is still drum. The question is what do I to get more pressure to the front. Everything is still stock accept the disc brakes. Still has the same drum master cylinder. Will I need a proportioning valve what master cylinder do I use and will I need to change my fitting to the hoses if changed. Thank you.

  25. Jay Fitzhugh says:


    Have you ever consulted on the correct master cylinder for an original Kinmont disc brake system? Many of the concepts presented such as bore size, residual check valves, fluid capacity, etc., may not apply. Thank you.

  26. reginaHolbrook says:

    I’m looking for a proportional valve for a 1969 98 olds but i was told that I need to one for dic brakes and the other for drum brakes but unable to find the can you send a picture of what both would look like

  27. Have 97 f150 4w drive,rear drum
    Change to disc from 03 f150 will
    Also put mc from same, the proportioning valve is completely different system
    What p valve do I need to install for correct braking

  28. I have a 71 442 that I converted to manual disk and now the pedal is very hard and little to no brakes. I have changed to position of the peddle rod and also the rear wheel cylinders. I am using the smaller bore master cylinder and larger rear wheel cylinder like the W30 came with from factory I would like some help if possible with this

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