Converting drum to disc kits

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Feb 2, 2014
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Location
Canfield, Ohio
My Car
1971 Mach I
OK guys, considering converting the front drum brakes on my '66 Mustang to disc. Yeah I know this a 71-73 site, but I also know some of you converted your 71-73 cars over as well. Looking for info on the kits out there today. Which ones are the best.? How did the installation go? Did you do the work yourself? Any surprises? Cost? Anything else you would like to add.

Thanks!
Mac
 
I did mine on my 71 using the SSBC conversion kit that also used the drum spindles.
I'm not sure if they are still in business, but they are the earlier Kelsey-Hays style, 67 I believe. A very easy swap, but took me longer because I also replaced all the brake lines with SS.
 
Dan at Chockostang has an excellent reputation for his disc brake conversion kits. He's an old school, no BS kinda guy. His kits use all factory style parts, so you can go to any parts store and buy replacements.

http://www.chockostangclassicmustang.com/discbrakepowersteering/discbrakeconversions.html
You know he's old school when the product comes with instructions on a CD. You'll need to go to goodwill to try and pick up something to get the pictures off the CD. :D
 
You know he's old school when the product comes with instructions on a CD. You'll need to go to goodwill to try and pick up something to get the pictures off the CD. :D

LOL, right? His website is probably made with Microsoft FrontPage too....
 
I used this kit for my front conversion. In the interest of being transparent, I bought from a mechanic friend for less than retail. Its for a 67 Mustang, but it bolted right up.

Pirate Jack Kit

I only did the fronts, and chose to remain manual vs go power assist. I also had to source a few things myself:

There were a few things I needed to address to complete the front conversion:
  • A disc/drum master cylinder. I got a 742 Maverick MC for a manual disc/drum car from Rock Auto
  • I chose to keep the distribution valve to keep the plumbing simple.
For the rear:
  • A residual brake valve from Jegs
  • An adjustable proportioning valve, also from Jegs
  • I plumbed these into the long brake line running under the floor pan. I spliced them in line, just where the pan bends up to make room for the rear axle. The prop valve instructions had me set right where I needed to be in terms of adjustment.
I am glad I did it, even with a manual brake setup - much better stopping action and easy to maintain. At some point I may go rear disc, but am willing to live with the rear drums for now.
 
Any time I see folks wanting to do a drum to disc conversion I roll out a document I have saved so I can copy/paste in some info I feel is pretty important. My niggest concern is to recommend only a high quality supplier of parts, and it looks like you already have several places to check out. But, I will provide the name of another supplier (below). The other cocnern is to advise of the need to NOT have a Residual Pressure Check Valve (RPCV) in any of the hydraulic lines used for the front disc calipers. RPCVs are only used for drum brakes, never for disc brakes. Okay, here comes the info I have on file:


When replacing front and/or rear drum brakes with disc brake components on a First Generation Mustang or Cougar you do not want to go cheap. This is a fairly serious, even if fairly easy, operation. Use high quality parts, preferably in a kit designed to do a full upgrade. I like Wilwood, a reputable brand with a lot of years in this end of the business. Here are the most important things to be aware of:



• Replace the Master Cylinder with one designed for Disc Brake systems. Often the MC bore size is different compared to Drum Brake system MCs. Also, for Drum Brake MCs the fluid outlet port(s) for drum brakes has/have a Residual Pressure Check Valve (RPCV) under the outlet port’s brass seat. The RPCV is needed for drum brakes to keep fluid pressure on the wheel cylinder cup seals so they do not suck air into the cylinders when the fluid cools off. But, for Disc Brake systems such a valve puts needless pressure on the caliper pistons and causes the pad to drag on the rotor under pressure. That results in reduced vehicle performance, overheating of the front pads and rotors, and rapid wearing of the front pads.

(10:30)


Replace all rubber brake lines if they are over 10 years old. They may look like they are okay, but they could have internal deterioration, or be cracking in the rubber walls, therefore weakened.

• Flush the old brake fluid and replace it with fresh DOT3 Disc Brake Fluid. DOT3 is totally compatible with Drum Brake hydraulic components, and differs from DOT2 Drum Brake Fluid in its boiling point is higher – which is needed for Disc Brake systems. Do not mix newer brake fluid types with DOT3 fluid. And never use petroleum fluids (oil of any type) - ever.

• Get a Power Brake Booster, as the Disc Brakes are not a self-actuating design like a Drum Brake system is. I have driven Disc Brake systems without a power booster before. No fun. They work, but power boosted Disc Brake systems are much better.



• Never use copper lines for hydraulic brake systems (Nickel-Copper alloy metal lines made for brake systems are fine). The copper metal alone is too soft and the lines can and will rupture if enough pressure is applied. Use only properly designed steel or Copper-Nickel alloy lines with double flare endings.

• Do not go cheap on brakes, suspension, or tires, ever.

For front disc calipers, be sure to put the calipers on the correct side, otherwise you will never be able to properly bleed the air from the hydraulic system. Refer to the attached file with its graphics, apparently created by Richard Ackerman (I got it from Dennis Keegan), to see how the calipers ought to be oriented.

Many thanks to Richard and Dennis for allowing me/us to share this excellent graphic.
 

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The other cocnern is to advise of the need to NOT have a Residual Pressure Check Valve (RPCV) in any of the hydraulic lines used for the front disc calipers. RPCVs are only used for drum brakes, never for disc brakes.

@mrgmhale - Not sure if this was about my post - but to be clear, I was not telling anyone to put a residual valve in the front brake line system. I described plumbing it into the rear lines, in a Front Disc/Rear drum setup, such as the OP was asking about.
 
Last edited:
Got mine done a few years ago, I also used the type that used the drum spindles with an adapter plate for the calipers. I paid a brake shop to do the work for me.
The kit used the same brake pedal, but required a new hole be drilled in it about an inch lower for a pin to be placed in it that lines up with the power master cylinder which sits lower than the drum master cylinder.
Also needed to change the brake light switch on the pedal to a power brake switch. The switches for drum brake and power brakes look identical, but the drum brake switch has a stronger spring in it and my rear brake lights wouldn't come on because the brake pedal no longer needed as much force on it to activate the brakes so the spring in the switch wasn't moving enough to trigger it.
I would encourage anyone to make this conversion; for me it was a game-changer that I could drive my car normally after years of cautious drum braking trepidation!
 
Any time I see folks wanting to do a drum to disc conversion I roll out a document I have saved so I can copy/paste in some info I feel is pretty important. My niggest concern is to recommend only a high quality supplier of parts, and it looks like you already have several places to check out. But, I will provide the name of another supplier (below). The other cocnern is to advise of the need to NOT have a Residual Pressure Check Valve (RPCV) in any of the hydraulic lines used for the front disc calipers. RPCVs are only used for drum brakes, never for disc brakes. Okay, here comes the info I have on file:


When replacing front and/or rear drum brakes with disc brake components on a First Generation Mustang or Cougar you do not want to go cheap. This is a fairly serious, even if fairly easy, operation. Use high quality parts, preferably in a kit designed to do a full upgrade. I like Wilwood, a reputable brand with a lot of years in this end of the business. Here are the most important things to be aware of:



• Replace the Master Cylinder with one designed for Disc Brake systems. Often the MC bore size is different compared to Drum Brake system MCs. Also, for Drum Brake MCs the fluid outlet port(s) for drum brakes has/have a Residual Pressure Check Valve (RPCV) under the outlet port’s brass seat. The RPCV is needed for drum brakes to keep fluid pressure on the wheel cylinder cup seals so they do not suck air into the cylinders when the fluid cools off. But, for Disc Brake systems such a valve puts needless pressure on the caliper pistons and causes the pad to drag on the rotor under pressure. That results in reduced vehicle performance, overheating of the front pads and rotors, and rapid wearing of the front pads.

(10:30)


Replace all rubber brake lines if they are over 10 years old. They may look like they are okay, but they could have internal deterioration, or be cracking in the rubber walls, therefore weakened.

• Flush the old brake fluid and replace it with fresh DOT3 Disc Brake Fluid. DOT3 is totally compatible with Drum Brake hydraulic components, and differs from DOT2 Drum Brake Fluid in its boiling point is higher – which is needed for Disc Brake systems. Do not mix newer brake fluid types with DOT3 fluid. And never use petroleum fluids (oil of any type) - ever.

• Get a Power Brake Booster, as the Disc Brakes are not a self-actuating design like a Drum Brake system is. I have driven Disc Brake systems without a power booster before. No fun. They work, but power boosted Disc Brake systems are much better.



• Never use copper lines for hydraulic brake systems (Nickel-Copper alloy metal lines made for brake systems are fine). The copper metal alone is too soft and the lines can and will rupture if enough pressure is applied. Use only properly designed steel or Copper-Nickel alloy lines with double flare endings.

• Do not go cheap on brakes, suspension, or tires, ever.

For front disc calipers, be sure to put the calipers on the correct side, otherwise you will never be able to properly bleed the air from the hydraulic system. Refer to the attached file with its graphics, apparently created by Richard Ackerman (I got it from Dennis Keegan), to see how the calipers ought to be oriented.

Many thanks to Richard and Dennis for allowing me/us to share this excellent graphic.

As per usual, you are a wealth of information.
 
Edit to my post #3. The kit I got also had the disc/drum master cylinder and a variable adjustable valve for the rear brakes.
I ran it for many years without a booster and to be honest, I didn't notice that much difference after I did install a booster.
 
@mrgmhale - Not sure if this was about my post - but to be clear, I was not telling anyone to put a residual valve in the front brake line system. I described plumbing it into the rear lines, in a Front Disc/Rear drum setup, such as the OP was asking about.
My mentioning the RPCV was not directed at any comment by you. This is general information I send as a post whenever I see anyone mentioning an interest in converting from drum to disc at the old master cylinder with front brake RPCV still in place, hence allowing a perpetual problem with the disc brake solution. My intent is to raise the awareness of that kind of potential problem.

That said, I felt your post was dead on.
 

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