Posted By: 71PurpleDodge
Want to upgrade 4 wheel drum to 4 wheel disc??? - 02/09/15 11:53 PM
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.
Posted By: feets
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? - 02/10/15 12:17 AM
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.
Posted By: RapidRobert
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? - 02/10/15 12:19 AM
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
Posted By: feets
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? - 02/10/15 12:23 AM
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.
Posted By: Steve Bryant
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? - 02/10/15 12:35 AM
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.htmlI 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.
Posted By: AndyF
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? - 02/10/15 01:04 AM
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.
Posted By: DAYCLONA
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? - 02/10/15 01:36 AM
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
Posted By: 71PurpleDodge
Re: Want to upgrade 4 wheel drum to 4 wheel disc??? - 02/13/15 02:10 AM
Thank you very much to all who responded. This will give me the info to help me move foward.
