Aftermarket rear disc brake conversion that does not axle modifications
 

Merry Christmas all!

Is there a disc brake conversion that fits over the factory axle hub and requires no modifications to the axle flanges/hubs? Also, do they cause a track width change?

This is for an 8.5 10 bolt rear with Moser axles.

Grivera most of the kits out there use the 79-81 Trans Am/Cadillac ratchet calipers-sometime problematic. The problem I have found with Moser axles is the rear axle brake pilot it too short to locate a hubcentric wheel and a rotor-as they are thicker than a drum. The rotors being thicker might increased the track 1/8". I think whatever kit you might see that issue.

Yes, our drum-in-hat setup will do this. It will move the wheel out 1/4" due to rotor thickness. You will need 15"+ wheels to clear.

You also will need longer studs as GM was very cheap here.

Edit: Like Skip said - the 1979-85 Caddy calipers can be problematic, hence our drum in hat setup which dispenses with them.

https://scarebird.com/image/cache/ca...ar-500x500.JPG

I have the same exact rear you do and used the right stuffs kit with no E brake provision. So it was really simple. Probably not the ratcheting calipers that are being discussed. They looked just like the chevelle calipers on the front IIRC.

It might have moved the wheels out a fraction. I can’t remember. It was a super easy install though. Way easier than the front. It certainly took me less time to install the complete retro kit than it would have to rebuild the drums. Might have been more affordable too than an all inclusive drum rebuild.

The hardest part is that stupid proportioning valve.

Blazer LS rear brakes...fits 15" wheels, has e-brake

If you have larger wheels(minimum of 17”) then you can buy a C6 based conversion system that Kore3 sells. I have F/R conversion kits that use the C6 Z51 brakes for a 73-77.
http://www.kore3.com/

The kit I used came from Pirate Jack's and at the time the same kit was offered through Inline Tube and Jegs as a "Bolt-on kit requiring only hand tools". The kit included a "love note" advisng the rear axle flanges required a corner radius to be machined for the rotors to mate with the axle flanges. Without the radius, the rotors did not fully seat. This may have been a BOP 8.2 10-bolt issue only.

They also neglected to mention you had to weld the tabs for the hardline-to-hose transition to the axle housing and also need to be able to shorten and double flare the rear axle brake lines. Just an FYI, that ain't ever going to work so you're going to have to buy a rear axle line set, shorten them and double flare the ends for connection in addition to welding the tabs in place. Pirate Jack's suggested I use hose clamps around the rear axle to secure the tabs in place or just eliminate them altogether and use nylon zip ties instead. I asked them if I couldn't just use told "bread twisties" for the full "ghetto engineering" effect.

Aside from requiring machining and welding, it was a bolt on installation lol. After I replaced the 2 leaking Eldorado rear calipers it worked out fine.

What I learned ... buy the caliper brackets from our Forumite and source the rest from reliable suppliers. Unless you're buying Wilwood, any component that can leak will leak, so buy your calipers and master cylinder from a store with a liberal over the counter return policy unless you're buying Wilwood and avoid no-name Chinese proportioning valves even if they look just like GM.


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https://imagizer.imageshack.com/v2/3...924/P5iMEG.jpg

Any particular years? I assume no kits on market with components?

Wheels are 15x7" Rally II

Do you have factory style axles/flanges or Moser?

Clean install - Although it sounds like a PITA - I do expect to flare lines and have tabs welded

I have Moser 30 spline axles.

I did have to weld on tabs. And I just used a couple of hard lines from Napa and bent them. You could make it better if you cut and flare lines. Mine are a little wacky because it was too long.

FYI: I (easily) grafted discs Strange Dana 60; 70-79 Rear Hats, 84 T/A Calipers and Emerg Brake cables.

Seems odd that no issues whatso ever since install, yet those rear Calipers were known to lockup due to mech Emerg shaft rust. Great Brake response using the G-Body Master CYL.

Yeah, the tabs they furnished were radiused to match the rear axle. The stock termination location of the hardlines was too far outboard to mount up anyway but I thought they could have easily punched the brackets for them maintaining the stock alignment and requiring only shortening the hard line termination.

I had a good laugh over their hose clamp and ziptie suggestion. I thought man oh man, what am I dealing with here?

Is this the kit you used?
https://www.summitracing.com/parts/rsd-afxrdm1/reviews

When H-O made rear disc brake kits, we supplied a spacer to keep the axle end play from pushing the pad back into the caliper and creating a low or zero brake pedal. a floating caliper design will eliminate this problem, but none of the designs I see pictured seem to support this.

What brakes do you have now? Typical 9.5" drums from an older compact/intermediate axle?

If so, consider merely upgrading to the 11.x drums from a newer intermediate like a 73--77, or a full-size car.

You get better, stronger brakes than what you have now, retain the park brake, zero issues with wheel compatibility, and they practically give away the parts at the Treasure Yard.

Verify or replace the springs and adjuster, cut the drums and replace the shoes as needed. Biggest problem is swapping the backing plates; and assuring that the shoe-contact pads on the backing plate aren't excessively worn. If they are, you can have the wear-grooves welded up and smoothed-out for little money.

Pretty-much all the advantages of the typical disc conversion, few problems.

OOPS ! I was thinking of our A Body conversion ! But check axle end play anyway

Yeah, I just looked up my old tracking email.

I used RSD-AFXRDM1 and RSD-PV72 for the prop valve.

Im fairly certain I didnt pay that much for it, but they may have been hit hard by overseas availability. I think I payed like $275. Oddly all that I can find is the tracking and not the order receipt with prices.

All in all though I installed it in 2019 and have had no problems with it.

Was yours an original front disc car? If so, did you swap the MC?

It was drum drum, but the car was a basketcase. Everything on it now is all new aftermarket.

So initially I bought a right stuff front kit, that came with a master and a prop valve for front disc rear drum.

Then I bought the rear kit when I swapped the 8.5 in. Kept the same master but switched to a disc disc valve.

I used a 1LE front brake set up for my 1976 Firebird. I also installed the 11" drum set up on the rear. It makes a big improvement for a lot less money. I went from 11" front to 12" front and 9.5" rear drums to 11" rear drums. I used a 1977 Lemans as a donor for the rear.