Do I Need Different Master Cylinder When Upgrading To Disc Brakes? Demco DA75 Brake Actuator

Question

Question:

I’m switching from drum to disc brakes. do I need a different master cylinder or is this ready to go?

asked by: Audrey

0

Expert Reply:

Audrey, this unit # DM33CV is factory-set up for disc brakes with the higher-pressure master cylinder already installed. So you’re good to go, no upgrades needed. Just make sure your lines are in good shape and you have some spare Dot 3 or Dot 4 fluid handy!
You'll love the disc brake upgrade; you'll wonder why you didn't do it sooner!

Did you have a reverse lockout kit on your old one?

expert reply by: Andrew N

0

Andrew N.

8/15/2025

Hey Audrey, how did the switch to disc brakes go? Did you find that everything was set up as expected with the master cylinder? I'm asking because I want to make sure others can benefit from your experience!

Answer 1

It does sound like there is a short to the brake controller through the wiring or in the internal circuitry of the brake controller. Since your brake controller shows no red light this indicates a short to the brake line (blue wire). If you are using…

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Answer 2

If you are only getting 1.5 volts at your brakes then there is an issue, but there is not a fuse that controls the brakes. There are a number of possible issues so you will need to find out if the issue is on the brake controller, truck, or trailer.…

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Answer 3

Hey Matt, thanks for bringing this to our attention. Yes the mounting hole dimensions of the Demco DA75 Trailer Brake Actuator for Drum Brakes #DM33CV that you referenced are separated by 3 inches horizontally and 2.5 inches vertically. Do you have a…

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Answer 4

Hey there Lorna. Yes, the Demco Drum Brake Actuator #DM28CV or Demco Brake Actuator Disc #DM33CV will 100% fit your 3" wide 4" tall trailer tongue. Even though the actuator says 3" wide and 2-1/2" tall, it will work because it…

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Answer 5

Great question, Hannah, and welcome to the world of boating and trailering! Since the Demco Disc Brake Actuator #DM33CV doesn’t include a lockout, you’ll want to add Demco Manual Lock Out Kit #DM93CV if you want to prevent the brakes from engaging…

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Answer 6

Dan, you’ll want to use 1/2" x 4-1/2" Grade-5 or higher for a secure mount. They aren't included, but you can find them at any hardware store. The mounting holes on the Demco DA75 Brake Actuator #DM33CV are standard size for bolt-on…

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Answer 7

There sure is! You'll be needing the Lockout Key #DX94FR for your Brake Actuator #T4606520. Do you use the key much? Or are you using the electric solenoid?

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Answer 8

Hey Howard! Yes, I think the Replacement Inner Member for Dexter DX7.5L Brake Actuator #DX97FR will replace what you have. It has the same body, just a different coupler on the end, so it will line up in the old housing. If you want to save some…

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Answer 9

The Demco Hydraulic Trailer Brake Actuator part #DM72VR should be a direct replacement for the Atwood 61101 Brake Actuator that you have now. This newest updated it rated at 7K instead of 6K. This is a bolt on option that mounts on 3" centers.…

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Answer 10

The manual lockout on your Atwood 85778 surge brake coupler is there so that you can back up the trailer without the brakes locking up on you. Yes you can safely tow your trailer with the broken manual lockout, you just have to make sure you…

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Do I Need Different Master Cylinder When Upgrading To Disc Brakes? Demco DA75 Brake Actuator

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