Disc brake converstion question

[rrTor-Red]

71 RR with HD power drums. I want to convert to discs. Does anyone know if the power booster for the HD drums work with discs? Is it sufficient? I'd like to keep my car near original as possible and dont like the after market GM booster types.

Thanks

 

[moparmarks]

Will work but not well. Won't have hard braking when needed. Get a 71 Midland Ross booster for disc form the Ramman.com.

 

[benno440]

yeh woont work well there are power boosters out there that look similiar to stock

 

[CTMopar]

I received from James the PST guy thats a member here. He said that they just came out with a factory style booster. You might want to contact him. SSBC emailed me and said that I could use my drum booster with their kit but he also told be that disc and drum cars came with the same booster.

 

[moparmarks]

Books shown different part# between drum and disc boosters.

 

[Propwash]

Rockauto is showing this as OEM for factory power Disc/ft Drum/rear....Cardone P/N 50-3705 '71 Roadrunner Guru's out there, is this the correct style?

http://www.cardone.com/Products/Product-Detail?productId=503705&p=rock

If so, rockauto sells them for $130 (including the core charge) for the booster/master/check valve combo. Be sure to keep your linkage off the backside of the old booster handy. Do not use a drum based Power booster on a disc/drum car. The power assist ratio's are completely different...They are not the same! You'll also need to add in a proportioning valve for the rear brakes when converting to disc.

Good luck rrTor-red

 

[CTMopar]

My Sport Satellite is a power 4 drum system and my brothers coronet is a disc front drum rear car. They have different boosters. They each look like the corresponding ones on autozone.com. Yet the person from SSBC emailed me that both drum and disc cars used same booster. Makes me wonder about their tech dept.

 

[Propwash]

My Sport Satellite is a power 4 drum system and my brothers coronet is a disc front drum rear car. They have different boosters. They each look like the corresponding ones on autozone.com. Yet the person from SSBC emailed me that both drum and disc cars used same booster. Makes me wonder about their tech dept.

I hear ya....I had a guy at Autozone a couple months ago tell me Ford and Chrysler used the same voltage regulators back in the late 60's.

 

[69Bee]

My 72 Plymouth service manual says that both manual and power piston bores to be 1 1/32" dia, but the reservoir is taller for the power master. The manual master also has two residual valves and the power mater only has one for the front chamber. Other than the power master missing the pushrod, they are the same.

 

[CTMopar]

I hear ya....I had a guy at Autozone a couple months ago tell me Ford and Chrysler used the same voltage regulators back in the late 60's.

At least at autozone it might just be some guy that happened to get a job at an auto parts store and only knows what the book says. SSBC is an after market brake company. They should know or at least do some basic research.

 

[Propwash]

My 72 Plymouth service manual says that both manual and power piston bores to be 1 1/32" dia, but the reservoir is taller for the power master. The manual master also has two residual valves and the power mater only has one for the front chamber. Other than the power master missing the pushrod, they are the same.

So the master cylinder for the power vs. the manual brakes are the same; besides different reservoirs, residual valves and pushrod......lol Sorry man, had to...feel free to dispatch the middle finger as necessary. :icon_blackeye:

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At least at autozone it might just be some guy that happened to get a job at an auto parts store and only knows what the book says. SSBC is an after market brake company. They should know or at least do some basic research.

No Doubt!

 

[69Bee]

So the master cylinder for the power vs. the manual brakes are the same; besides different reservoirs, residual valves and pushrod......lol Sorry man, had to...feel free to dispatch the middle finger as necessary. :icon_blackeye:

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I was half way thru my post about different bore sizes (run into that before, but mid 70's maybe), and decided to check the manual. I was befuddled too. You would think there would be a bore size difference. I have seen other specs that listed a difference of 1 1/8" and 15/16" or so, but that must be for mid 70's as I said before.

 

[CTMopar]

I will leave of the first couple of emails with SSBC but here is my last two and their replies.

Me: My car has factory power drum brakes. This is a different booster than a car that had power disc brakes from the factory. Would I need to get a disc brake booster or will the drum one work?

SSBC: Your booster is the same as a disc brake booster, nothing more to buy.

Me: OK, they are not the same though. My brothers car is a factory power disc car. His booster is much larger than mine. From talking with people who have converted using factory parts they needed to change to the disc booster for proper operation.

SSBC: A booster is a booster, there is no such part as a disc brake, or drum brake only booster. They simply lessen the amount of work, your leg has to do and are sized to fit the vehicle. Regardless of what brakes are on the axle.
What do you make of this conversation? I am thinking that my money might be better spent elsewhere.

 

[69Bee]

I will leave of the first couple of emails with SSBC but here is my last two and their replies.

Me: My car has factory power drum brakes. This is a different booster than a car that had power disc brakes from the factory. Would I need to get a disc brake booster or will the drum one work?

SSBC: Your booster is the same as a disc brake booster, nothing more to buy.

Me: OK, they are not the same though. My brothers car is a factory power disc car. His booster is much larger than mine. From talking with people who have converted using factory parts they needed to change to the disc booster for proper operation.

SSBC: A booster is a booster, there is no such part as a disc brake, or drum brake only booster. They simply lessen the amount of work, your leg has to do and are sized to fit the vehicle. Regardless of what brakes are on the axle.
What do you make of this conversation? I am thinking that my money might be better spent elsewhere.

I don't think there is any real difference, except for the size and shape difference between a Bendix, Midland Ross, or another manufacturers booster. The only differences I have seen so far are the ones I talked about earlier, and to include 2 and 4 bolt masters depending on the year you are talking about.

 

[moparmarks]

Well the 70/71 parts book has a listing for drum and a listing for disc. Different Bendix booster between drum and disc. Same with Midlands. On my 72B someone converted it from power drum to disc leaving the drum booster on there. Pedal was hard and didn't stop like it should. I got a rebiult Midland Ross booster for disc and what a difference.

 

[Propwash]

There is a difference between power boosters from Drum and Disc/drum as far as power assist ratio's and like moparmarks pointed out with his cars issues, they're not made to be universal with each other. If so, there would be a universal booster across the board for drum and for disc. There would not be "Disc Brake Car" or "For drum brake car" when it came down to shopping/surfing for a booster. I agree that size/dimensions definitely take effect into the engineering of the boosters.

That email is absolutely stunning CTMopar...For a company that specializes in brakes, you would think someone would have a little more insight and give a bit better advice.

 

[CTMopar]

That email is absolutely stunning CTMopar...For a company that specializes in brakes, you would think someone would have a little more insight and give a bit better advice.

That's why my money will be going to PST. I left a PM here for James. The next day he replied with answers to all my questions. The same day I received an email from someone else at PST that said James had forwarded my questions to them also. This email provided more information and technical data. This level of attention along with the fact that they have come out with a factory fit after market booster as opposed to the ones that mount forward and up from the firewall has earned them my $$. The 10% FBBO discount doesn't hurt either.

 

[Propwash]

Same here...PST was very helpful in the few times I used them as well. I can't remember who I spoke with but last time I called them, but I was impressed how informed and correct he was. I dealt with Just Suspension a few days later and they were an absolute joke compared to PST. Girl on the phone sounded like she was 15, and that was their product line adviser? I had to tell her three times my roadrunner was a B-Body and not an E-Body and coil springs belong on children's park toys and not my mopar.

 

[rrTor-Red]

Thanks for the replies. My intention is to switch from drums to discs all the way around. The concern is the booster. I need to do more research to see if I need a booster specifically for discs or not.

 

[flypaper]

disc's all the way around?
you can get away without a booster if the parts are properly balanced...
with 4 wheel disc set ups, it comes down to the piston size of the rear calipers.

remember,... you are changing out to different parts that will now cause a reaction
somewhere else in the system...

the reservoir for disc brakes is larger then drum,it needs more volume of fliud to push it.
if you notice, the disc/drum master cly has one side larger then the other.
not good for rear discs,not enough fluid to push them....

your options for a master with 4 wheel discs are
you can either try a newer lightweight aluminum 2 bolt max pressure one with the 4 to 2 bolt adaptor plate as long
as your rear caliper pistons aren't too big for it?
(dr diff carries everything)

or go to baer or wildwood as they carry masters that might work also with the 4 disc systems they offer.
another option is to retro fit a master for the application,like fron a car that came with 4 wheel discs
like a viper but that is alot of work and opens all new cans of worms...

a booster (no matter what kind) and a disc/drum master cyl
will not work very well with 4 wheel discs.....lol

you really need to be more specific with exactly what you are doing here
so you get a more proper answer...