Author Topic: Rear Axle Disk Brake conversion kit Q's (Read 1390 times)

gomopar440 · « **on:** July 17, 2006 - 11:22:15 AM »

I'm looking at adding disk brakes to my 72 Chally. It has the factory power brake system with front disks and stock drums on the 8.75 axle. Last time I was working on my car I had to kick the brake pedal hard to losen it up enough to even move. I'm planning on going through the entire system and making a few changes. The power booster will probably get heaved and the master cylinder will be replaced with an aluminum one off a newer disk brake car or truck. The original brakes will get rebuilt to stock specswith some decent modern pads for better bite. Out back is where I am having trouble nailing down what I'm going to do. So, I have A few questions for everyone here:

Have any of you had experience with swapping disk brakes onto a drum brake axle?

If so would you recommend them to anyone else?

What are my options as far as sources? Companies? Kits? are there other OEM Mopar sources for a straight up R&R conversion?

Thanks

Troy · « **Reply #1 on:** July 17, 2006 - 11:50:27 AM »

Talk to DoctorDiff (http://members.aol.com/doctordiff/) - he sells several different kits. I think Scarebird makes some as well. You can find kits from Wilwood, SSBC, and Master Power too I believe but I like DrDiff's kits (and they are less expensive). Unfortunately, my only running,driving car doesn't have rear discs yet so I can't give you a real life comparison. Physically bolting them on isn't all that difficult - especially if you're upgrading master cylinders and/or proportioning valves. Most anyone who knows anything will tell you that rear discs are totally unneccessary for performance/drivability but I like the look.

Troy

gomopar440 · « **Reply #2 on:** July 17, 2006 - 12:32:13 PM »

I have been looking closely at the Scarebird pieces since I'm trying to keep the cost down on this. I've talked to them on the phone already but to get what I need the cost for their stuff starts to approach the costs of some of the other cheaper kits. What I mean by that is that I'd have to get them to buy the rotors for the kit and machine them and ship them out to me with the caliper brackets. The caliper brackets from Scarebird, with the rotors already machined to their specs, will cost me about $320 shipped to PA. From there I'd still need to get the calipers, pads and hoses. It could be done, but it's kind of a pain for me to go chasing the parts everywhere like that.

I should mention that I'm currently stationed (Navy) in Puerto Rico and I have to fly out to PA to even be able to work on my car. I don't really have a car available to me while I'm there to chase after parts whenever I want. That makes it very tough to try and get things from the store or drop stuff off at machine shops to get them worked on. So, I have to get everything ready to go over the internet or phone and have it shipped to PA so when I get there I can just pick up the tools and get cranking. It's tough, but that's just the way I have to operate in order to even make any progress on the car at all.

As far as being neccisarry (sp?), yea, I know they will be overkill for daily driving. However, I'm putting a 512ci wedge in the car and making it light/balanced as possible in hopes of playing with it in some SCCA/Autocross/Drift/Silver State/One Lap type events (rules pending ofcourse :p ) some time down the road. I'd just rather not spend money on any drum brakes that I know will just get pitched in favor of disks eventually.

Troy · « **Reply #3 on:** July 17, 2006 - 01:16:26 PM »

Check with Doctor Diff then. Here's a run-down of what's included in the kit I bought:
"Kit includes Cobra calipers with parking brake provision, pads, 11.7" or 10.7" rotors, billet aluminum caliper brackets, stainless flex lines and hardware. Light, easy to install and super-clean. $575"

It fits Dana or 8 3/4" rearends and I don't believe you are required to run green bearings. A huge bonus is that replacement parts are as close as the nearest Ford dealer (or auto parts store). The Wilwood kits are somewhere near that price but you're hosed if you need replacement parts while stranded out somewhere. He also has a new 13" Cobra front brake setup that runs about $800 with the hubs, bearings, rotors, calipers, seals, and lines. You'll need 17" wheels obviously.

According to Andy at AR Engineering (makes Viper front disc conversions):
"For SCCA road racing I'd use the 13 inch kit up front and 10 inch drums in the rear. You'll need to have a really fast car (150+mph on the straights) before you need rear discs. At least I'd recommend starting with that combo and prove that you need more brake before spending the money."

My car is a 73 Barracuda so the combo shouldn't change much for you.

Troy

HemiDog · « **Reply #4 on:** July 17, 2006 - 01:23:07 PM »

One thing to keep in mind is if you ever decide or have a B-body spec rearend in an E-body is to see how the parking brake is set up on the rear. I ran into a problem because the brake sits closer to leaf spring. The parking brake mechanism on the Baer brakes I have would not allow them to be mounted. I solved the problem by "re-clocking" the brake to the front of the rotor instead of the rear. At that point there is still complications to overcome if you have a rear swaybar.

gomopar440 · « **Reply #5 on:** July 17, 2006 - 01:47:42 PM »

Thanks Troy. I tried to check the link you posted but it wont work here at work. I'll check it out when I get home.

That kit for $575 sounds about like what I'm looking for. Do you know what's the minimum wheel size you need for the 11.7" rotor setup? I currently have 14" Magnum 500's on there just to hold the car up while I'm working on it.

I'm planning on running 17X8 and 17X12 wheels but not right away. The front 13" upgrade kit will have to wait till after I get the new wheels obviously. LOL!

Well I already have a 200mph spedometer and plan on running 3.2X or 2.7X rear gear with a 727 and a GV OD unit if that tells you anything about expected operating velocities

I'm not really worried about changing the rear out anytime soon unless breakage becomes a regular occurance. I've already minitubbed the car and still have to put in the 3" spring relo kit yet. After that the housing will get braced to keep it all rigid. If I ever change the axle, it's going to need the perches moved over and the brace reinstalled at the least. With the relo I'm probably going to have to use a splined type sway bar. There will probably be a bunch more small details like that that will need to be worked out before all is said and done.

Troy · « **Reply #6 on:** July 17, 2006 - 02:30:11 PM »

You should be able to get by with 15" wheels on 11" or 12" rotors. Ask Cass to be sure. Depending on the dish, some wheels may not clear the wider calipers (although the factory fit 11"x3" drums on there with no problems). I have no idea what that much of a narrowed rearend will mean as far as the parking brake is concerned.

Troy

gomopar440 · « **Reply #7 on:** July 17, 2006 - 03:11:38 PM »

Quote from: Troy on July 17, 2006 - 02:30:11 PM

I have no idea what that much of a narrowed rearend will mean as far as the parking brake is concerned.

Huh? The axle width is still the stock E body dimentions. The springs and perches are what's getting moved inward. How would that affect the parking brake?

Troy · « **Reply #8 on:** July 17, 2006 - 03:34:11 PM »

Whoops, sorry - I sort of assumed that you'd be narrowing it since it's mini-tubbed with a 3" spring relocation.

Troy

gomopar440 · « **Reply #9 on:** July 17, 2006 - 03:50:09 PM »

Naw, I kinda want the extra width of the E body axle. The tires and wheels are where I'll make use of the extra room. On those 17" rims I'm going to use 245's up front and 335's out back.