Rear disc brakes....

[Freddie's Buick]

Anyone know how to convert the early 80's G-body 7.5 rear drum brake system to discs using boneyard parts from various GM's? (Good question for Eric).

I'd also love to use a better front rotor set-up with slotted disc. (I know my 1981 won't use later ones).

 

[turbobob924]

watching as well

 

[Not Avg 6]

Good one, just curious how it would hold boost.

 

[Freddie's Buick]

I read in a Haynes manual that the G-body Buick did offer 4-wheeled disc brake as an option from 1977 on up. I looked in my Buick manual and there it was.....how to repair rear disc brakes. But I have'nt seen an 80's G-body Buick with rear disc brakes yet.

This website sells a kit with the OEM rear calipers and fabricated mounting brackets:

10-12 BOLT REAR DISC BRAKE WHEEL KIT (RWBK1012) - Performance Online


Wilwood makes front aluminum calipers that with an easy mod, (cutting the ears off of the spindles), bolts them on. Dynalite vented 10.75" rotors finish off the upgrade.

But I'm sure this stuff may be found as OEM in bone yards. SOMEONE OUT THERE HAS TO KNOW!

 

[turbofish38]

The big problem is the axle flange used on the G-body. It's the crappy 3 bolt Direct Torque. Now you will find all over the 'net articles on guys cutting the flanges to use the 3rd gen Camarobird parts but IMO cutting the flange and drilling the holes larger is not leaving enough meat on the flanges. That link is a generic kit that will only work with the old style 4 bolt flange. I know companies out there that make a kit for the 3 bolt flange. It's pricey as to be expected. No bolt on boneyard parts anyway. That must be a blurb in the Haynes. GM did have a 4WDB option on every RWD chassis but the G-body.

One of those Rivieras sitting in my drive has the 4WDB option. It uses the same 10.5" rotors on all four corners with the same single piston metric calipers. Not much difference in stopping between the drum cars and the disc cars that I can tell anyway. At least it will be easy to add the larger 12" rotors when the time comes. I'm using a mix of parts from a 4th gen F-body and a 00-05 vintage Bonneville SSEI.

 

[Freddie's Buick]

....The big problem is the axle flange used on the G-body. It's the crappy 3 bolt Direct Torque. .....That link is a generic kit that will only work with the old style 4 bolt flange......

Did you check out the drawing at the bottom of the link? Maybe the drawing is awkward but it looks like the kit is for a 3-bolt flange. I'm looking at the fabricated mounting brackets and they look like they are 3-bolt?

Maybe I'm missing something?

How 'bout those calipers? They look like the GM ones on the front except for the emergancy cable springs.

Yep those kits are pricey. I figured braking should be better but I guess I could be wrong.

Too bad a boneyard would'nt help much either...
I got an E-mail respones from Summit.com and they only sell kits for 8.5 rears. Darn!

 

[turbofish38]

Thats definetly a kit for the old 4 bolt flange. I'll try and dig up a pic for the 3 bolt. Basically same style of flange but they have a big 1 inch diameter dowel that positions the plate in the wheel cylinder hole.

 

[turbofish38]

Here's a link to the pricey kit. I couldn't make the pic big enough to show the detail in the backing plates. Performance Suspension Technology - Grand National, Cutlass, Monte Carlo, Regal 1982-88

The better calipers or should I say kits have the integrated parking brakes that use shoes riding behind the rotors like all of the late model trucks or Corvette. Those spring loaded jobs like to freeze up if you dont use the park brake every once in awhile.

 

[Freddie's Buick]

Yep....saw that site too.

And you're right.....too high end for me. Boneyard is my cup of tea.

 

[charlief1]

Two different options. You can use an s-10 rear disk or 4th gen camaro set up if you're willing to modify the axle flanges or check out smileys.com (dirt track) for some weld on or bolt on conversion parts. I've got everything to do 2 axles but I havent had the time or the space. If you use the later camaro or s-10 unit you will have to cut and modify the axle flanges but it will allow you the least expensive and most effective of the two. Charlie

 

[charlief1]

If you wnat to go to a larger front rotor you can also use the S-10 blazer spindles and rotors off of a 2002 or newer. It's a hat type set up with a dual piston caliper.

 

[cutlassMike]

What about rear disks form 80s era Cadillacs? They have the same 10 bolt axl {abit wider} and same general suspension/E break set up {triangle 4 link/foot actuated E break}? There is also the blazer that comes with 4WDB?


I can't see GM producing different axl housings/mounting flanges for a optional breaking system. I am of the opinion that the above doner car's rear break parts would bolt on a G body 7.5/8.5. There is also the issue of proportioning valves, master cylender, booster and residual valves needed in 4WDB conversions.
I could be wrong about the above assumtion and would welcome any info to the contuary.


Is there a differance between break mounting flanges on 7.5 and 8.5? I have both in my shop and I can't see a decernable difference {BUT, I haven't dissasembled the 8.5 just yet}.

 

[turbofish38]

Is there a differance between break mounting flanges on 7.5 and 8.5? I have both in my shop and I can't see a decernable difference {BUT, I haven't dissasembled the 8.5 just yet}.

As far as cars and trucks with the 9.5" drums go...no. They all use the wimpy Direct Torque, 3-bolt mounting flange. One exception is the B-Body. It uses the old stand by 4 bolt axle flanges. If you want to bolt on any type of factory disc brake than you have to modify the flange.

 

[82grandBeast]

here try this link http://universalcarlifts.com/product_info.php?products_id=144 its a 78 to 88 g-body big brake kit

 

[sowle]

Rear disc

Calipers- caliper adapters- and related hardware from Cadillac Seville's 77-78 will bolt directly to any GM 10 bolt and 12 bolt axle. 79 Seville's have a different casting number on the caliper's- these I'm not sure about, but I'll bet they are a plus. The rotors are 5on5- but Pontiac WS6 rear rotors are a bingo and slide right on. There should be a few companies that make these in slotted- drilled bla bla bla. Make sure you grab the e-brake divider, these are unavailable. E-brake cables are tough to find but if you shake the right bush you will find new ones. I rebuild calipers myself- kits are readily available, but remans are out there- core value is huge though. I haven't had time to have mine on the road so I 'm not sure about master cylinders and proportioning valves, this just takes some more homework. Good luck