Disc Brake Conversion question

[tomps]

So I've made the decision to convert from power drum to power disc brakes on my 70 Challenger, at least in the front initially. However, I'm getting some confusing info from some of the suppliers that is not consistant and was wondering if you guys might know the answer.

As I mentioned, I current have a factory power drum set up. Some places have told me I can use the existing booster but need a new master cylinder. Others have mentioned need to replace both while still some other info suggests I can just use my existing master cylinder and booster?? I don't want to have to modify the firewall to accept a booster that doesn't easily hook up if I need a new booster.

I know I can use the existing spindels. I plan on keeping the factory 14" wheels so that seems to limit a few choices as most require 15" wheels. Was trying to keep it to a 1 piston caliper but most kits seems to lead to a 4 piston which is fine just not really needed.

Anyone have any experiences with a particular kit/supplier both good/bad. SSBC seems to have a few kits that I think will work just a little confused still? Any input greatly appreciated!

Thanks!

-Mark

 

[challenger6pak]

I would guess that most if not everyone is telling you correctly. The companies do not want to sell parts to you that won't work; especially brake parts. They know what works with their products. I have to use drum spindles for my Wilwood brakes. Of course I tossed all of the drum spindles when I converted to factory disc. The main reason I see to go to aftermarket brakes is size. There are other advatages such as drag on the rotor, weight, heat tolerance and displacment so your brakes don't fade from multiple stops at high speeds. None of these things will really factor into a regularly street driven car. If you want 14 inch wheels, I would just go with a factory 71 - up set up. The 70 set up has berings that can be harder to get if you need to service them.

 

[moparleo]

Actually the bearings and rotors changed in 73. The rotors are half the price of the earlier rotors. It depends on what you want to spend and how close to stock do want to keep your car. You can do a stock upgrade with spindles,calipers,rotors from a number of companies out there in the $500. to $700 range. They use all new parts and are complete. No fighting with rusted or crossthreaded parts. You will need a new master cylinder as the disc brake pistons are much larger than the old wheel cylinders. You need more volume and the disc brake m/c has more capacity for the front brakes. You will also need a proportioning valve to control front and rear line pressure. If you have the coin, do it completely now and you will get many years of safe braking.

 

[challenger6pak]

Thanks Leo. I forgot the year change.

 

[challenger6pak]

Thanks Leo. I said the wrong year. Too much to remember anymore.

 

[challenger6pak]

Oh well. First my post did not show. Then both of them showed. I tried to delete the second one and am told I am not allowed.

 

[tomps]

Interesting and informative guys!

I should have added that the car I'm doing is a 70 RT/SE and will be driven lightly. No racing, an occasion show/cruise night etc.. I am keeping the car as stock/original as possible. This is the only non-original option I'm adding...strictly for driveablitiy and safety. I'd rather spend the money now as that engine is out, new inner fender going on and everything will be off for painting so might as well upgrade now while it's all off.

-Mark

 

[moparleo]

Hope I gave you some usefull info. I have to remember this stuff before I forget it ?/. Or something like that.

challenger6pak, your'e ok with me.

 

[challenger6pak]

Mark, are there any pics of your car on another thread? RT/SE's are nice cars. Is it a 383 car? I would love to see some pics.
Tod

 

[tomps]

Mark, are there any pics of your car on another thread? RT/SE's are nice cars. Is it a 383 car? I would love to see some pics.
Tod

Yes...under Member Restorations I have some pics. It's a 383 auto, PW, power drum brakes, music master radio, front leather seats, A/C (all there) car although the engine is not original to the car. It is a period correct 383. The VIN # is different with a build date of April 1970 (my car was January of 70). I can only trace some history of the car back to the Carolinas in the mid 90's. Other then that all checks out. Still has the original radiator support with VIN staming and cowl stamping. It's undergoing a framo on restoration currently. No rust anywhere but it need a freshening for sure.

My 1st E-body. 10 years ago I owed a 68 Roadrunner post car with a 440/4 speed. always wanted an E-body though!

So I'm waffling again on the brakes but leaning towards just to changing the master cylinder and add the stock disc brakes to the front. The current power drums do stop the car excellent. I did recieve a new master cylinder wit hthe car but it's got 2 equal size bowls so it's set up for drum/drum I'm guessing.

Leo...i have the same problem...I'm always forgetting things lol!!

-Mark

 

[71solo2challenger]

The simplest setup for you would be using the 73-76 A/E body disc setup. It uses the most readily available parts.

First thing you will need is a disc brake mastery cylinder. You cannot use a drum M/C with disc brakes.
The spindles/caliper adapters are now being reproduced. Magnumforce and other vendors carry them. In a pinch you can also use the 73+ B/F/J/M/R spindles and caliper adapters.
Key thing here is to stay with the 73+ as the the 70-72 spindles use a smaller inner bearing. Not really a big deal as Dr. Diff carries a spindle sleeve to use the later rotors on those, but it is something else to remember.
Calipers need to match the caliper adapters (pin or slider) and you will need the proper flex hoses to mate.

Personally, I would run the 73 spindles, run pin type caliper adapters and pin calipers (as that was what was stock on our e-bodies), and run the 73+ 10.87" brakes in your application. You'll be able to run your 14" wheels, have readily available rotors (nearest auto parts store) and you won't have to worry about the flex hose (yes a consideration). Just make sure to mount your calipers to the front like the factory!

 

[challenger6pak]

Does your dash VIN match the cowl and core support VIN?

 

[tomps]

Does your dash VIN match the cowl and core support VIN?

They all match yes indeed.....

Thanks for the input 71solo2challenger :icon_smile:

 

[challenger6pak]

Cool.