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Front Disk Brake Conversion not working ( UPDATE11/15)
#1084391
09/28/11 05:01 PM
09/28/11 05:01 PM
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Joined: Jun 2006
Posts: 135
Pittsburgh, PA
1970440RT
OP
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OP
member
Joined: Jun 2006
Posts: 135
Pittsburgh, PA
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I have a 1970 Challenger w/ power drum brakes originally. I wanted to change over to front disk to improve my stopping ability, there was nothing wrong with the drums, just wanted to upgrade. I bought the master cylinder from Ehrenberg ( 1 1/4" bore?) and the spindles are out of a 73 B body. The bearings, hoses, and discs are new, the calipers are rebuilt-pin type. I retained the original hard lines, power booster, and distribution block. I bought a Wilwood adjustable prop valve from Mancini to be able to adjust the rear drum lock up. Everything went together well and the front brakes do work, just not well. No matter how I adjust the prop valve, the rears lock up first while testing. I can turn the dial on the proportionaing valve all the way to the stop at "less brake" and the rear drums still lock up before the fronts, if the fronts lock up at all. I deduced the line pressure was not enough to operate the calipers so I bought another master cylinder, a 7/8" bore to increase the line pressure but after another test, I get the same result; the rears lock up before the fronts. The brakes pedal feels only marginally better. I have another problem that I found out after I assembled everything, the calipers and caliper brackets are off a B body and put the caliper in a position to interfere with the lower control arm if I turn too hard either way. I guess I need M body calipers ( not sure on that either ...  ) and brackets to fix this but before I buy anything else, I need to address the lack of front disc brake performance. Anyone else experience this problem before? I did a search and found a ton of brake conversion info but nothing similar to what I'm experiencing. Any suggestions what to look at first?
Last edited by 1970440RT; 11/15/11 08:37 AM.
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Re: Front Disk Brake Conversion not working as expected
[Re: 1970440RT]
#1084392
09/28/11 05:21 PM
09/28/11 05:21 PM
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Joined: Jan 2003
Posts: 451
So. Cal. For Now But Texas Bou...
69sixpackbee
mopar
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mopar
Joined: Jan 2003
Posts: 451
So. Cal. For Now But Texas Bou...
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Your interference problem is because you used the '73 B spindles. You need the '73-4 E or '73-6 A units. Do not use the similar, but taller, knuckles from ‘73-up B and F/J/M/R-body cars! I am using the slider-type of calipers and the fat rotors.I too use a master that is 7/8" but I also changed the rear wheel cylinders to a smaller 7/8" diameter one. I did not use the adj. prop valve but rather the "A" body unit that I got the donor spindles from. Just make sure you have a residual valve in your master for the rear brakes.
I have not had one bit of trouble.
Bud
Last edited by 69sixpackbee; 09/28/11 05:30 PM.
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Re: Front Disk Brake Conversion not working as expected
[Re: 69sixpackbee]
#1084393
09/28/11 05:38 PM
09/28/11 05:38 PM
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Joined: Jan 2003
Posts: 75,004
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,004
U.S.S.A.
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Quote:
Your interference problem is because you used the '73 B spindles. You need the '73-4 E or '73-6 A units. Do not use the similar, but taller, knuckles from ‘73-up B and F/J/M/R-body cars!
Bud
How does a spindle that is 3/8" taller cause the caliper to hit the LOWER control arm ?
To the OP , what exactly is hittng the lower control arm ? Did you mount the caliper to the front or the rear? Also the lower control arms on a 73 B body are the same as your 70 B body .
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Re: Front Disk Brake Conversion not working as expected
[Re: 1970440RT]
#1084394
09/28/11 05:41 PM
09/28/11 05:41 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Quote:
Any suggestions what to look at first?
Might "bench" bleed the M/C then (re) bleed the fronts EDIT is the clearance on the booster pushrod good (~1/8")? I'd check that 1st
Last edited by RapidRobert; 09/28/11 05:44 PM.
live every 24 hour block of time like it's your last day on earth
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Re: Front Disk Brake Conversion not working as expected
[Re: Fury Fan]
#1084396
09/28/11 05:48 PM
09/28/11 05:48 PM
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Joined: Jan 2003
Posts: 75,004
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
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U.S.S.A.
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Quote:
One thing that jumps out at me is you re-used the drum booster. A drum booster will not provide enough boost for discs in a heavy stop. It will work for normal use but not give enough braking whn you really need it.
I don't really think that's your problem, though, but it's something to investigate and correct.
I was thinking the same thing and was going to ask if the drum and disc used the same booster in a 70 up E body , I know that 66-69 B body they use a different booster.
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Re: Front Disk Brake Conversion not working as expected
[Re: 1970440RT]
#1084400
09/28/11 06:27 PM
09/28/11 06:27 PM
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Joined: Jan 2003
Posts: 27,467
So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,467
So Cal
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Quote:
Wow, thanks for all the quick responses.
The current calipers are mounted to the rear as factory 73 B's come standard. The caliper is hitting the lower control arm where the banjo bolt connects the rubber line. I have a "stop" I engineered to prevent the arm from crushing the fitting or caliper. My car is a 70 E body and after doing some more research, this interference is common when trying to adapt a B body setup to an E body.
I never thought the boosters would be different and my current one is a little rough so I can start there.
I have bled and re-bled the masters and lines thinking that was my problem but I still have the same issue.
So the brake line is hitting the lower control arm? Is it the hard line extension comming off the banjo. Some are like 1" long, then goes to soft line.
You should be able to front mount those calipers like 70 Challengers original had. That usually takes swapping the calipers from side to side so the bleeder is on top. But it's finding the right brake lines for them. You might be able to leave the caliper as they are and just get/find the right brake line.
This should be just like fitting a 73-76 A-body slider type caliper conversion. So you would use the same brake line those swap use. I sure though the 73 B-body shared the same caliper as the A-bodies did?? Or at least had the same brake line inlet orientation.
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Re: Front Disk Brake Conversion not working as expected
[Re: Stanton]
#1084405
09/28/11 08:49 PM
09/28/11 08:49 PM
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Joined: Jun 2006
Posts: 135
Pittsburgh, PA
1970440RT
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OP
member
Joined: Jun 2006
Posts: 135
Pittsburgh, PA
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Quote:
Just a thought ... are your caliper bleeder screws at the top or bottom? They should be at the top - air rises.
The bleeders are at the top.
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Re: Front Disk Brake Conversion not working as expected
[Re: Challenger 1]
#1084406
09/28/11 08:51 PM
09/28/11 08:51 PM
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Joined: Jun 2006
Posts: 135
Pittsburgh, PA
1970440RT
OP
member
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OP
member
Joined: Jun 2006
Posts: 135
Pittsburgh, PA
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Quote:
You also need the disc brake proportioning valve, not the drum brake distribution block.
I do have an adjustable proportioning valve but also left in the distribution block.
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Re: Front Disk Brake Conversion not working as expected
[Re: AndyF]
#1084407
09/28/11 09:00 PM
09/28/11 09:00 PM
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Joined: Jun 2006
Posts: 135
Pittsburgh, PA
1970440RT
OP
member
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OP
member
Joined: Jun 2006
Posts: 135
Pittsburgh, PA
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Quote:
Did you read Ebergs disc brake article? He is pretty clear on why the B body calipers won't work.
Get calipers that are designed to be rear hung with a rear mounted hardline. Then get some custom hoses made and that problem will be solved.
Andy, this should solve the interference problem (which I'm aware of the mistake I made now). I did read E's article but apparently mixed up some of my info.
Unfortunately, I still have the terrible brake performance issue.
Also, I checked at NAPA and they list the same part number for the drum and disc booster.
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Re: Front Disk Brake Conversion not working as expected
[Re: 1970440RT]
#1084408
09/28/11 09:20 PM
09/28/11 09:20 PM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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After you get the right disc brakes on your car, this is what I was talking about. The top one is for a 71 challenger with power disc brakes. The bottem one is the power 4 wheel drum brake distribution block. They don't funtion the same way. I did the this swap on my 71 and used rear 11" drum brakes that were on the car and it works great. Better than my 74 with factory power disc brakes with 10" drums in back. I run a adj proportioning valve in my rear brakes line too, but that is a different deal for brake tuning, not setup. I'm thinking 1970 is the same? Someone here will know.  71 power disc brake proportiioning valve, and the steel brakes lines are different also.I ordered all new lines from Fine Lines for a power disc brake car and everything bolted up and fit fine.Used factory correct rubber hoses, nothing custom. I used 73 E body spindles and brakes. 
Last edited by Challenger 1; 09/29/11 08:10 AM.
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