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Want to upgrade 4 wheel drum to 4 wheel disc??? #1750218
02/09/15 07:53 PM
02/09/15 07:53 PM
Joined: Jan 2003
Posts: 561
New York City and Cape Cod Mas...
7
71PurpleDodge Offline OP
mopar
71PurpleDodge  Offline OP
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Joined: Jan 2003
Posts: 561
New York City and Cape Cod Mas...
Want to feel a little safer when driving my 1971 Challenger. Would like to hear from those that have done it as well as those who are considering this and do I want to use parts off other years/body's or modern kits designed for this. Thanks.

Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: 71PurpleDodge] #1750219
02/09/15 08:17 PM
02/09/15 08:17 PM
Joined: Jan 2003
Posts: 28,068
Irving, TX
feets Offline
Senior Management
feets  Offline
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Joined: Jan 2003
Posts: 28,068
Irving, TX
It has been done countless times.

You can drop the money for a kit or come up with your own stuff.

For a typical use car it's easier to follow the road well traveled and get the relatively inexpensive kits out there. Dr Diff has some good stuff.

SSBC and some of the other popular companies out there have a tendency to use oversized master cylinders which leads to a super hard bake pedal.

Be aware that if you go larger than 11.75" rotors you might run into clearance issues with 15" wheels. Some multi-piston calipers can cause wheel fitment issues too.


We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: 71PurpleDodge] #1750220
02/09/15 08:19 PM
02/09/15 08:19 PM
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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RapidRobert Offline
Circle Track
RapidRobert  Offline
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
I've heard that going to 4 wheel discs is great and others say it is the cats' a$$. Doc (on here) has kits and his rep for parts/service/tech is unsurpassed. I have a pair of SBP and BBP rotors and I am going to weld brackets to the 8&3/4's for slider discs but I ain't got to it yet. I'm thinking the only thing that could trip me up is the axle endplay but I am going to get it right at zero & see how it turns out. Not a specific ans but here's a BTT for ya


live every 24 hour block of time like it's your last day on earth
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: RapidRobert] #1750221
02/09/15 08:23 PM
02/09/15 08:23 PM
Joined: Jan 2003
Posts: 28,068
Irving, TX
feets Offline
Senior Management
feets  Offline
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Posts: 28,068
Irving, TX
I ran the 4 wheel AMG brakes on the hot rod for years and never had a problem with axle thrust. I had factory style bearings and no provision for end play adjustment.

I know I put more than 13,000 miles on the car like that but I did check it when I put it together.


We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: 71PurpleDodge] #1750222
02/09/15 08:35 PM
02/09/15 08:35 PM
Joined: Aug 2013
Posts: 518
Georgia
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Steve Bryant Offline
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Posts: 518
Georgia
Last year I converted the front brakes on my 1970 Barracuda and I followed the Disc-o-tech instructions and it worked out great. http://www.moparaction.com/tech/archive/disc-main.html

I bought lowered (2") Spindles from PST just to drop the nose a tad and I bought the caliper adaptors from E-Bay. The calipers, master Cylinder and booster I got from the local parts store. Aside from the PST calipers I don't think I paid more than $400 for the rest. As yet, I have not converted my rears and I may not. The rears are not used as much and most of the local guys prefer drums in the back.

The lessons I learned are:

1) Buy the MC new if possible. I bought a rebuilt one and it was defective.
2) Buy a name brand prop/dist valves if you are going back to stock. I should have bought inline first instead of the cheap Ebay valves I tried to use.
3) Go ahead and replace the metal lines while you are at it. Mine were full of crud and they are not that expensive.
4) Many people prefer the pin-type calipers and I am no exception.

Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: feets] #1750223
02/09/15 08:46 PM
02/09/15 08:46 PM
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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RapidRobert Offline
Circle Track
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Lincoln Nebraska
Quote:

I ran the 4 wheel AMG brakes on the hot rod for years and never had a problem with axle thrust.


That's reassuring. Thanks Feets


live every 24 hour block of time like it's your last day on earth
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: 71PurpleDodge] #1750224
02/09/15 09:04 PM
02/09/15 09:04 PM
Joined: Jan 2003
Posts: 31,045
Oregon
A
AndyF Offline
I Win
AndyF  Offline
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Posts: 31,045
Oregon
Everything you need can be sourced from www.doctordiff.com

Probably the first step is to just put the 11.75 front disc brakes on there and leave the rear drums alone. That setup should be good for any street car. It will also for track use up to 120 mph or so. The 11.75 kit requires 15 inch wheels.

If you want to step up to bigger brakes then you need larger wheels. I run 13 inch rotors on my '65 Coronet but I have 17 inch rims.

Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: RapidRobert] #1750225
02/09/15 09:10 PM
02/09/15 09:10 PM
Joined: Jan 2003
Posts: 28,068
Irving, TX
feets Offline
Senior Management
feets  Offline
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Joined: Jan 2003
Posts: 28,068
Irving, TX
Quote:

Quote:

I ran the 4 wheel AMG brakes on the hot rod for years and never had a problem with axle thrust.


That's reassuring. Thanks Feets




Please note that I did verify the thrust when I built it.

Unless you're in the differential for an axle or bearing swap you can set it and forget it.


We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: 71PurpleDodge] #1750226
02/09/15 09:36 PM
02/09/15 09:36 PM
Joined: Dec 2007
Posts: 18,157
Mass
DAYCLONA Offline
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DAYCLONA  Offline
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Joined: Dec 2007
Posts: 18,157
Mass
I've been doing the 4 wheel disc upgrades on customers cars for a decade +, if your budget is under $1000, I'd recommend you source factory front calipers/rotors/knuckles/brackets/etc for up front, generally I prefer the 2 pin 70-4 B/E body calipers, your choice on going 10.95 or 11.75 front rotors, and or later full floater calipers...


for the rear, I generally prefer the SSBC rears, which are Thunderbird rears, or the Dr Diff Cobra rear set up, your choice...

If you go with SSBC don't use the master cylinder/power set up, just junk, run a Mopar master, I generally run a Bendix dual diaphram booster and a disc/drum master in the 1" to 1 1/8" bore max depending on the caliper bore sizes chosen front to rear...

If you do a full 4 wheel disc conversion, you don't need a factory proportioning valve, you could use your factory drum distribution block if desired...I generally prefer to run the rear line directly off the master, same with the front, except you need to tee somewhere during the run from the master to both front wheels,...if you can't achieve a 70/30 to 60/40 front/rear brake bias choosing the proper sized calipers, you may have to install an adjustable PV valve in the rear line to raise the front bias to the desired ratio...

If your going to use a booster, I generally use either the single or dual diaphram units (Chrysler/Midland/Bendix) generally I find the single boosters are good for about 800 -1000 psi line pressure, and the dual diaphram Bendix units I've achieved as much as 1500 psi, but 1200+ is avg for the dual Bendix....

Don't take no short cuts, buy quality stuff, replace any lines or components you suspect are worn/junk, there's plenty of help here on Moparts if you get jambed up on your install

Mike

Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: AndyF] #1750227
02/10/15 05:04 AM
02/10/15 05:04 AM
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog Offline
Striving for excellence
Kern Dog  Offline
Striving for excellence

Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Quote:

Everything you need can be sourced from www.doctordiff.com

Probably the first step is to just put the 11.75 front disc brakes on there and leave the rear drums alone.




I feel like Kid Rock following Mick Jagger here since Andy F is well respected, but here goes:
I had the 11" discs and 10" drums in my 70 Charger and it stopped great. I didn't like seeing the brake drum through my rear spokes so I decided to switch the rear to discs by buying a kit from Dr Diff. Great stuff, no complaints with the quality, but....Rear discs made no difference in my car. They made no difference in my friends 71 Challenger. These cars stop great with the disc/drum setup. If the rear wheels lock up too easily, you can step down one size in rear wheel cylinders until the front locks before the rear. If I was running Rally wheels or Magnums where you couldn't see through them, I'd stick with drums. Shoes are cheap and the design carries with it OEM reliability.

Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: Kern Dog] #1750228
02/10/15 11:14 AM
02/10/15 11:14 AM
Joined: May 2007
Posts: 952
Queens, N. Y.
FASTBACK340 Offline
super stock
FASTBACK340  Offline
super stock

Joined: May 2007
Posts: 952
Queens, N. Y.
Quote:

I feel like Kid Rock following Mick Jagger here….




Wow…. Mick never had a voice, and K/R never will! Some analogy…..


I was about to do a rear disc kit, but:

I'm running close to the wheel openings now. The rear disc push the track out further….. I'm not springing for a new set of tires or narrower rims.

Master cylinder choice and proportioning is another potential grey area. We have too many cars coming into our shop with brake issues from these conversions; low or poor brake pedal being the #1 complaint.

Cost: One kit is approx. $325, the other is almost TWICE that. Then there's the "name" stuff for even more.


I run steelies w/ dog dishes so it's not an "appearance" thing. I just wanted the best brakes with the least mout of issues. I want to drive my car this season, not spend my weekends and nights figuring out pedal ratio's and port pressures for marginally better brakes. Once researched, it just don't make sense to me.


Now, if it was Mick Jagger following Cory Taylor…..


`68 Barracuda 340-S
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? [Re: FASTBACK340] #1750229
02/12/15 10:10 PM
02/12/15 10:10 PM
Joined: Jan 2003
Posts: 561
New York City and Cape Cod Mas...
7
71PurpleDodge Offline OP
mopar
71PurpleDodge  Offline OP
mopar
7

Joined: Jan 2003
Posts: 561
New York City and Cape Cod Mas...
Thank you very much to all who responded. This will give me the info to help me move foward.







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