[Ken K]

There are different ways to add disc brakes to 64-72 GM A Body cars. The first way is to add 67-72 disc brakes from a donor car, these are just about bolt ins. The second way is to add disc brakes and spindles from a 70-81 F body or 73-77 A body, this is called the tall spindle conversion. The third way is to add disc brakes and spindles from a 78-87 G Body or S10 brakes and spindles, most people are unaware of this conversion. The height of the spindle between the ball joint on stock spindles is 7.125 inches, the height of the G body-S10 spindle is 7.5 inches and the height of the F body tall spindle is 8.75 inches. To convert 64-72 A body cars to tall spindle disc brakes you must use different upper and lower ball joints, the part number for TRW upper ball joints is TRW #10268 and for Moog upper ball joint is K5208. The lower ball joints must be turned down in a lathe .080 to fit the lower control arm, the part number for TRW is #10277 and for Moog is #K6145. You must also use an offset upper control arm shaft made by Moog to avoid excessive shim pack or buy after market upper control arms. You must also use tie rod ends from a 73-77 A body, the G body tie rods ends may also work but I am not shure. The tie rod ends screw right into the 64-72 adjustment sleeves. To use G Body-S10 spindles and brakes use the same upper and lower ball joints and tie rod ends as the F body tall spindle conversion. The best part of using the 78-87 G Body-S10 conversion is you don't need after market control arms or offset upper control arm shafts. Another good thing about using The Late Model G body-S10 conversion is the price, you can use almost all new parts inexpensively. You can also buy new after market 2 inch drop spindles for less than $150.00 and stock type G body-S10 spindles for less than $100.00, Disc Brakes rotors are less than $30.00 new and rebuilt loaded calipers are less than $20.00 each, front brake hoses are less than $10.00 each. The tall spindle conversion will make your car handle better. The G body-S10 conversion will allow you to use original style Rally 1 wheels and vintage mag wheels without rubing or locking up your calipers.

[Ken K]

There are different ways to add disc brakes to 64-72 GM A Body cars. The first way is to add 67-72 disc brakes from a donor car, these are just about bolt ins. The second way is to add disc brakes and spindles from a 70-81 F body or 73-77 A body, this is called the tall spindle conversion. The third way is to add disc brakes and spindles from a 78-87 G Body or S10 brakes and spindles, most people are unaware of this conversion. The height of the spindle between the ball joint on stock spindles is 7.125 inches, the height of the G body-S10 spindle is 7.5 inches and the height of the F body tall spindle is 8.75 inches. To convert 64-72 A body cars to tall spindle disc brakes you must use different upper and lower ball joints, the part number for TRW upper ball joints is TRW #10268 and for Moog upper ball joint is K5208. The lower ball joints must be turned down in a lathe .080 to fit the lower control arm, the part number for TRW is #10277 and for Moog is #K6145. You must also use an offset upper control arm shaft made by Moog to avoid excessive shim pack or buy after market upper control arms. You must also use tie rod ends from a 73-77 A body, the G body tie rods ends may also work but I am not shure. The tie rod ends screw right into the 64-72 adjustment sleeves. To use G Body-S10 spindles and brakes use the same upper and lower ball joints and tie rod ends as the F body tall spindle conversion. The best part of using the 78-87 G Body-S10 conversion is you don't need after market control arms or offset upper control arm shafts. Another good thing about using The Late Model G body-S10 conversion is the price, you can use almost all new parts inexpensively. You can also buy new after market 2 inch drop spindles for less than $150.00 and stock type G body-S10 spindles for less than $100.00, Disc Brakes rotors are less than $30.00 new and rebuilt loaded calipers are less than $20.00 each, front brake hoses are less than $10.00 each. The tall spindle conversion will make your car handle better. The G body-S10 conversion will allow you to use original style Rally 1 wheels and vintage mag wheels without rubing or locking up your calipers.

[Triggerman]

Do all three conversions give you the very same rotor diameter? Also, do you end up with the same size and style of caliper? Do these have any effect on which master cylinder you are using? Thanks, TM

[Ken K]

I had to go out and look. The rotor size of the F body spindle is 11 inchs, the rotor size of the G body spindle is 10.5 inchs, I don't have a 67-72 A body rotor to measure but I believe it is also 10.5 inchs. The calipers for the 69-72 A body is the same as the F body calipers. The calipers for the G body-S1o are slightly smaller in physical size. The brake pads on the 69-72 disc brakes are the same size as the F body 73-77 A body brakes, the brake pads on the G body-S10 are smaller and have less surface area. The caliper piston size on the 69-72 A body and F body is 2.75 inchs and the caliper piston size on the G body-S10 is 2.375 inchs. As far as what master cylinder to use there are many choices, the holes on the fire wall of GM vehicles is the same for many different years. If you want more brake pressure use a master cylinder with a bigger piston. If you have a big cam and don't have much vacuumn you can use a master cylinder from a 1970 Firebird with manual disc brakes.

[Scott Misus]

What about the '77-'90 GM full sizers? I read in one of the glitter magazines that this was a doable swap. They said that it gives you the bigger rotors. This is kind of nice, however, I've never felt that A body disc brakes were inadequate anyway. That is, I've experienced brake lockup under heavy application (indication that the brakes were adequate), and NEVER, EVER experienced brake fade or other inadequacies. Thus, I never felt the need for high end Baer stuff. Perhaps Tom McQueen can fill us in on this improvement, as he's done it.

[Scott Misus]

Addressing the master cylinder: You can use, with brake line adapters, the aluminum master cylinder from the '77-'90 big cars as well. LOTS lighter than the cast iron slugs.

[Ken K]

I think I may have solved part of the problem of using the tall spindle conversion on a 64-72 A body. I had a 79 G body upper control arm and placed it on top of a 64-72 A body upper control arm, the contours are the same and the width is the same but they are about 1 inch shorter. I looked up some info on one of the after market suspension suppliers and there is a picture of tubular control arms and a stock 64-72 upper control arm, it looks like the tubular control arm is the same as a 78-87 G body upper control arm except it is not made out of stamped steel. The problem of trying to use the G body upper control arm on a 64-72 A body is that the spread on the upper control arm shaft bolt holes is different and it will not bolt to the 64-72 A body frame. It is not as easy as using the 64-72 upper control arm shaft on the G body control arm because the bushing mounts are wider on the G body spindle. If someone could figure out what upper control arm shaft would fit into the G body spindle and bolt to the A body frame, I think you could do away with the offset control arm shafts and excessive shim packs to convert the tall spindles to a 64-72 A body.

[Tom McQueen]

I have the Baer disc brake setup for the 9" ford rearend going in the GTO. I am also using the B-body spindles and Baer front disc kit. Rears are 12". Fronts can be either 12" or 13". My GTO came with front discs, and I am selling (hint, hint) the complete brake system (including booster and spindles). My reason for upgrading has nothing to do with any inadequacies the stock setup had. I just wanted a modern 4 wheel disc setup.

[Will]

The late '70s to late '80s or early '90s (not sure on the exact years unfortunately) B-body spindles are direct replacements for the '70 - '81 F-body spindles. Therefore, they can also be used in the A-bodies as mentioned above with the special ball joints and modified upper control arms.

Many of the B-bodies were equipped with 12" rotors from the factory, usually cars with towing packages or heavy duty suspension or brake options. I have two sets of these spindles, one set came from a '78 GP cop car and the other came off an '86 Caprice wagon.

The problem with these 12" spindles is finding a reasonably priced rotor. The rotors that come on them originally have a 5x5 bolt pattern and I'm not so sure redrilling the rotors for the correct pattern will work as the area of the rotor where the studs go through it is reinforced around the existing stud holes and relieved elsewhwere.

This leaves your best choice for a brake rotor as the late '80s Camaro/Firebird 1LE rotors, which are about $100 each new and are designed for a metric wheel stud, though you can find SAE studs that will fit. They take the same wheelbearings and will bolt right up to the B-body spindles.

As to the need for larger brake rotors, it has more to do with repeatability under extreme conditions than any lack in the stock system for normal use. For a normal street-driver, the F-body or original A-body sized rotors are fine. If you intend to autocross or roadrace then you will need the biggest brakes you can get, and if you're on a budget then the 12" rotors are the way to go.

[Ken K]

...

[Poncho64]

Does anyone know where I can get the offset Moog control arm shaft? Or at least the part number, I wanna do the tall disc brake conversion and I have all the other stuff but cant find the control arm shaft?

[Will]

Any parts store that sells Moog suspension components ought to be able to get it for you.

I recently had to purchase new upper control arm shafts for my Nova and the ONLY ones I could find anywhere are the offset shafts, no one even makes non-offset replacement shafts. I didn't realize how big of a PITA this was going to be. Junkyard units are not an option, they would have the same problem my originals had, which was that the factory decided to weld the nuts to the threaded portion of the shafts to ensure they would never back off, thus making it impossible to replace the upper control arm bushings without cutting the shafts out.

Now that I spent nearly $50 each for the shafts, I can't align my car properly anymore. With the shafts turned around to provide maximum negative camber, there is too much negative camber, like 5 degrees or more if any caster is dialed in. With them turned around the other way, I can't get any negative camber, nor any positive caster dialed in.

This sucks. I'm pretty much going to have to throw away over $100 in parts to correct the situation.

Sorry, this really has nothing to do with your question... Just venting.

[Poncho64]

I hate to keep bringing this topic up but I just have one more question. How hard is the swap to do? I just was at an all pontiac car show and was talking to your typical car guy know it all who showed me how he had done the tall spindle conversion and said it was a nightmare and that even with the offset shafts it just would not work and he ended up having to use the hotchkiss control arms. I want to do this swap on my daily driver lemans and I want it to be fairly straight forward, I dont want the car to be down for a week or so while I scrounge up the parts to do it. Has anyone done the tall spindle swap and is it really that bad?

[Ken K]

If you don't have a set of 69-72 A body disc brakes I would use the G body-S10 spindles if you don't want a lot of headaches. You don't need the offset upper control arm shaft or the special tubular control arms with the G body disc brakes. You can buy the shaved down lower ball joints from Global West or Hotchkiss.

[Tom McQueen]

I am doing the tall spindle swap. You need either the Global West or Hotchkiss arms. I am not familiar with retrofitting an offset shaft to the existing arms. You will also need a cut down ball joint to marry your lower arm to the new tall spindle. Also, I discovered (yesterday) that the adjustable HAL shocks will not slide thru the bottom of the A-arm without some minor clearancing. There wont be room for the plate nuts, so I have to weld the nuts to the A-arms. Remember the old saying...."bolt ons dont". There are several gotchas with this swap, but (Im told) the handling improvement is well worth it. I guess time will tell.

[Jason H]

If you where to use the s10 spindles could you use the rotors from an F-body (up to 81)?
If you use the F-body spindles and rotors then you need to use the new upper a arms. Correct? Can you use the Camaro upper arms instead?

Has anyone ever used rear discs off of a 81 f-body on a 68 lemans 10 bolt?

Jason

[JLHarper]

Anyone else have any experience with aftermarket disc brake kits? How do they perform, same as the old OEM discs, a little better, or alot better?
Any surprises going on? Mods needed?
Thanks...Jeff

[Ken K]

Which after market disc brakes? Some of the ones you see advertised in the back of magazines use some used and reconditioned parts, you are just buying the convienience of not having to recondition some of the parts your self.

['ol Pinion head]

Personally, I do not like the looks of the "big boys" underhood brake componets & for what you get, the price.

The master cylinders are not original appearing & IMHO, their dinky looking new brake boosters look like they belong on a cheap street rod.

Another BIG complaint is their goofy looking latemodel brass proportioning valves & (BIG COMPLAINT)lack of prebent lines to plumb them up. The bend it yourself lines & an adj prop valve nearly always look hacked in. In comparison, in my A-body changeover kits, I use original prop valves for the make & model of car OR supply a '71-72 GTO cast iron style proportioning valve. As an example, on '68 driver type A-bodies which would originally, if optioned, had 4 piston disc brakes, we will go back with the '69+ single piston caliper brake setup & a complete new (Inline Tube) brake line set for a '69 GTO.

On early birds or cramos (short of concours cars), I use a variation of the later 71+ Nova disc brake prop valve set-up & custom bent lines. This prop valve will be mounted utitilizing a small stamped steel bracket which mounts the cast iron style prop valve inline under the master cylinder...makes for a clean installation. James at Inline Tube offers a similiar "conversion" kit.

Also the "big boy" kits do not include hose mounting brackets, but usually include new brake hoses which require that you grind the hole out on your old drum brake hose brackets.

It all amounts to what you want detailing wise.

[This message has been edited by 'ol Pinion head (edited 07-25-2001).]

[JLHarper]

Ken, to reply to your question... some of the disc brake kits I have seen are...Master Power Brakes, Performance Suspension Compontents, Master Power Brakes and one of the guys on here installed Baer Disc Brakes kit I think. I havent looked at this one yet.
Another look at the above sources and one does look like a rebuilt GM setup though the add dosent say.
Old PH was right when he said tht the parts are bulky and different looking. I dont remember if these were his exact words, and to tired to go back and find out, but the point was correct. Many of the boosters and master cylds. look like some kind of Hobart comercial kitchen equipment.