Brakes: To be disc, or not to be disc

Ed Wagner

Ed Wagner

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Hi. I have a '70 Chrysler with drums all around. I purchased a used stubframe from a 71 (mine rusted out) and it has disc brakes. Thus far I have gleaned that I will need a different master cylinder, but what else do I need to do to use the 71 disc brakes? I believe there is issues with proportioning valves when you have drum/disc setup, correct? And is there upgrades to 71 brakes that would be beneficial for a non-modified vehicle?
 
Ed Wagner said:
Hi. I have a '70 Chrysler with drums all around. I purchased a used stubframe from a 71 (mine rusted out) and it has disc brakes. Thus far I have gleaned that I will need a different master cylinder, but what else do I need to do to use the 71 disc brakes? I believe there is issues with proportioning valves when you have drum/disc setup, correct? And is there upgrades to 71 brakes that would be beneficial for a non-modified vehicle?
Click to expand...
You'll need the disc brake master and brake hold off valve if you use the drum prop valve or the one piece prop valve that was used 72-73 possibly 71.
 
Ed Wagner said:
Hi. I have a '70 Chrysler with drums all around. I purchased a used stubframe from a 71 (mine rusted out) and it has disc brakes. Thus far I have gleaned that I will need a different master cylinder, but what else do I need to do to use the 71 disc brakes? I believe there is issues with proportioning valves when you have drum/disc setup, correct? And is there upgrades to 71 brakes that would be beneficial for a non-modified vehicle?
Click to expand...

You will need a disc brake booster unit if you are going to do power brakes with the appropriate master cylinder. Also need a brake portioning valve. Front brake hoses should also be replaced at this time. Correct booster is a Bendix dual diaphragm unit, fit 68-70 C-Bodies, some 71's were also equipped with this booster. Disc brakes are always going to stop better than drums. The question then becomes if you were happy with the braking performance with the factory drum brakes, you might consider keeping them. Otherwise do the conversion, the Bendix boosters are getting hard to find, so it might take some wrecking yard searching to find the correct booster.

Dave
 
You can also get aftermarket boosters as well, but a little bit modifications will have to be done, Like i did in my 68 Monaco
 
The only brake line reproduction supplier that I know of that has the correct lines is The Right Stuff linked below:

The Right Stuff - Disc Brake Conversions, Pre-Bent Lines, Brakes and More

I would personally go with the regular steel lines as the stainless steel ones are hard to seal well enough to prevent leakage at the fittings.

Your vehicle is a 70 model that used a brake hold off valve as stated above when equipped with disc brakes, but the 71 systems didn't have that part. So you could go with a 70 system and mount the hold off valve on the left front frame member and the accompanying disc brake proportioning valve for 1970 or you could go with a complete 71 system that didn't have the brake hold off valve, but you would need to go with the 71 proportioning valve mounted on the frame just below the master cylinder.

The 70 systems had 5 front brake lines you would need or if you go with the 71 style it would have 4 front brake lines (no hold off valve). The hold off valve was an attempt to minimize rear brake lock up on panic stops but wasn't really that effective.

There were no upgrades to the 1971 drum brake systems that would make them more effective to my knowledge. One of my cars came from the factory with drum brakes, and any hard braking from freeway speeds was pathetic, leading to almost immediate fade and long stopping distances. The cars should have never been released with them on a Chrysler when discs were readily available. I got rid of mine immediately and went to the disc system. A world of difference.
 
When I converted my 68 TC wagon to disc I installed the proper, or equivalent brake booster and MC, and just ran the front caliper line circuit straight off the master cylinder, and then put a manually adjustable brake pressure valve on the rear circuit. Been driving it this way for at least 10 years with no issues.
 
saforwardlook said:
Dante's doesn't make their own parts as far as I know, so they might well be getting the lines from The Right Stuff.
Click to expand...

Gotcha... found his prices to be more then fair...when i needed some covert parts , he was pretty good .. Maybe gets a better discount then us average folk :lol:
 
Wow. Lots to digest!

In reply to "am I happy with current braking".....HAAAAHAAAHAAAA. NO! Lol, tap the brakes and it throws you through the windshield (and pulls right): stomp on them and it feels like one of those falling out of bed nightmares. You wonder if you're ever going to hit bottom. I was excited to get there and this frame still had all the disc brakes, and tires even. Anyone want any 20 year old "vintage" bias ply tires? :)
 
Does ANYONE on this site know how to read... !!!!

He has a stub frame...
It came with control arms, spindles, and DISC BRAKES....
It also came with proper portioning valve ....

He needs a master cylinder for disc brakes.....


K.I.S.S.
 
Xenon...

FYI....For proper disc brake function you need the correct dual diaphragm brake booster. Will it still stop with the drum brake booster with a disc brake MC...sure it will in everyday casual driving environment, but in a panic/emergency stop situation the booster will not have the power to really lock up those big rotors and calipers and you could end up in a bad situation.

And yes we all read what he has and wants to do, we have all passed on lots of good and different points of view from our years of experience and all should be considered.
 
Ed Wagner said:
Hi. I have a '70 Chrysler with drums all around. I purchased a used stubframe from a 71 (mine rusted out) and it has disc brakes. Thus far I have gleaned that I will need a different master cylinder, but what else do I need to do to use the 71 disc brakes? I believe there is issues with proportioning valves when you have drum/disc setup, correct? And is there upgrades to 71 brakes that would be beneficial for a non-modified vehicle?
Click to expand...
If it has the crappy rotors that were really upgraded by Chrysler later on you might try to go to 1973s I think? I don’t know for sure because I’ve got power drum and they’re fine for what I do. I think they’ll panic stop at least one time in a row Lol!!! I just don’t know if it’d be worth the trouble to do it EXCEPT that you lucked out and got everything you’ll need. That would be the only way I’d ever upgrade to the “old” stuff. New style heck yes but the big old discs on my 71 Torino aren’t much more confidence inspiring than my power drums on the Fury. It’ll be an upgrade just don’t expect them to change the rotation of the earth. Believe it or not the old stuff ain’t that great it’s just great compared to the lesser old stuff. If you get what I’m saying...

Good luck and post your successful swap for us spectators. We’ll be rooting for you!!!
 
The Goose said:
If it has the crappy rotors that were really upgraded by Chrysler later on you might try to go to 1973s I think? I don’t know for sure because I’ve got power drum and they’re fine for what I do. I think they’ll panic stop at least one time in a row Lol!!! I just don’t know if it’d be worth the trouble to do it EXCEPT that you lucked out and got everything you’ll need. That would be the only way I’d ever upgrade to the “old” stuff. New style heck yes but the big old discs on my 71 Torino aren’t much more confidence inspiring than my power drums on the Fury. It’ll be an upgrade just don’t expect them to change the rotation of the earth. Believe it or not the old stuff ain’t that great it’s just great compared to the lesser old stuff. If you get what I’m saying...

Good luck and post your successful swap for us spectators. We’ll be rooting for you!!!
Click to expand...

'73 has a different rotor and spindle set. Rotor was the same size but the hub on the inside was made larger to accommodate a larger inner bearing due to the increased diameter of the spindle.

Dave
 
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