Low cost A-body disk brakes

[joe_padavano]

I originally posted this in the Brakes section, but it probably makes sense to put it here for more to see. I've also expanded the previous answer (which was specific to 1968 cars) to cover all 64-72 A-body cars.

There are a number of high dollar disk brake conversion kits for the 64-72 A-body cars. These kits are very complete, but also very expensive (well, at least by my cheap-@$$ standards). If you're willing to do a little work ordering from multiple sources, here's a low-cost way to convert any 64-72 A-body drum brake car to factory-size disks:

First is the basic brake kit. Here's the cheapest I've found.

http://www.speedwaymotors.com/p/4618...Brake-Kit.html

Spindles: $125/pr
Brake kit: $240
Hoses: $20/pr

Total: $385

Note that you still need a disk brake master cylinder and proportioning valve.

If you don't care about complete correctness, a replacement M/C is $16 from Partsamerica:

http://www.partsamerica.com/productd...pe=230&PTSet=A

Since I assume you're not looking at the megadollar four piston calipers that were factory on the 68s, this M/C will work fine. If you want the correct looking M/C, you can get this one for $59:

http://cgi.ebay.com/ebaymotors/67-68...QQcmdZViewItem

The 67-70 cars used an in-line proportioning valve shown here for $85:

http://cgi.ebay.com/ebaymotors/67-68...QQcmdZViewItem

This mounted below the M/C and has the advantage of not requiring you to disturb the distribution block on the frame. If that's too pricey, you can substitute a 71-72 combo valve shown here for $55, but you'll need to do more plumbing:

http://cgi.ebay.com/ebaymotors/GM-Di...QQcmdZViewItem

Then there's the issue of the brake lines. If you use the early-style proportioning valve, you only need to bend new lines from the rear outlet of the M/C to the prop valve to the distribution block. Take off the one old line and cut, bend and reflare the ends to plumb the prop valve, or bend up two new shorter ones to replace it. If you go with the combo valve you may need to replace or rebend all the lines. In any case the flare nuts going to the M/C may have different thread and you'll either need adapters (available at most auto parts stores) or get the right flare nuts and reflare the ends of the tubes when you replace them.

Finally, there's the issue of the frame brackets for the rubber hoses to the front wheels. If you want to do this on the cheap, you can file the holes in the current brackets, but the easy way is to just buy these for $25:

http://cgi.ebay.com/ebaymotors/69-70...QQcmdZViewItem

OK, so what's the total?

$385 from Speedway, $16 for the M/C, $55 for the combo valve, and $25 for the brackets gets you disk brakes for $481. If you want the correct M/C and prop valve, its $554. Either way, this is substantially less expensive than the complete kits, at the cost of some extra ordering time for you. If you like to scrounge, you can find parts even cheaper on ebay or at swap meets.

If you have power drums now, the disk brake M/Cs shown above will bolt to any 67-72 power booster (drum and disk brake boosters are interchangeable). The 64-66 cars with single brake systems use a different pushrod length in the booster and the dual circuit M/C will not work with it. You'll need to either get a 67 power booster or an aftermarket booster. If you have manual drum brakes and want to keep manual disks, (my 70 W30 stops fine with manual disks) then just get the correct manual disk M/C and transfer the pushrod from your drum M/C. If you have manual and want power, you'll need a brake booster in addition to everything above.

[68Tom]

Wow, thanks Joe. I was actually considering converting my front power drums to disc, as the brakes are completely shot on my car. However, after a little research, I learned that if you have 1968 SS I Rallye wheels, disc brakes will not fit, as the offset won't allow it. So, it's either new, non-matching wheels (would have to get the '70 SS I) or just replace the drums.

[joe_padavano]

Originally Posted by 68Tom

Wow, thanks Joe. I was actually considering converting my front power drums to disc, as the brakes are completely shot on my car. However, after a little research, I learned that if you have 1968 SS I Rallye wheels, disc brakes will not fit, as the offset won't allow it. So, it's either new, non-matching wheels (would have to get the '70 SS I) or just replace the drums.

You are correct that they won't fit, but the problem isn't the offset, it's the design of the wheels themselves. Prior to disk brakes becoming common, GM used wheels that had a smaller center disk and a deeper drop in the rim portion of the wheel. This made mounting tires easier and cleared the 9 1/2" drum brakes. Once disk brakes made their appearance in 1967, GM came out with a new wheel design that used a larger center disk and less of a drop in the rim. This cleared the calipers. Unfortunately, during the 1960s GM built both types of wheels and the early SSI wheels are the older style deep drop/small center design. Only the 1970-up SSIs will clear the factory 10.5" disks.

[OKIEOLDS]

If I do this conversion on my 70 cutty vert will the 15 inch rally wheels work on it and are the bolt pattern the same on the later wheels?

[joe_padavano]

Originally Posted by OKIEOLDS

If I do this conversion on my 70 cutty vert will the 15 inch rally wheels work on it and are the bolt pattern the same on the later wheels?

All SSII and SSIII rims (14x6, 14x7, and 15x7) will clear the FACTORY disk brakes with the 10.75" rotors. All three versions of the SSII/III rims were factory available with these brakes and I have personally bolted them all to various A-bodies that I've owned. As noted previously, with aftermarket disk brake kits that do not use the original style brackets and calipers, there's no gaurantee

[Maverick]

Was there a 14 x 5" ? I had a set of SSI's from a '69 Cutlass Supreme that I tried to put on my '71 442 with discs. They wouldn't clear .

Just asking .

Brent

[joe_padavano]

Originally Posted by Maverick

Was there a 14 x 5" ? I had a set of SSI's from a '69 Cutlass Supreme that I tried to put on my '71 442 with discs. They wouldn't clear .

Just asking .

Brent

Scroll up to post #3 in this thread:

Originally Posted by joe_padavano

You are correct that they won't fit, but the problem isn't the offset, it's the design of the wheels themselves. Prior to disk brakes becoming common, GM used wheels that had a smaller center disk and a deeper drop in the rim portion of the wheel. This made mounting tires easier and cleared the 9 1/2" drum brakes. Once disk brakes made their appearance in 1967, GM came out with a new wheel design that used a larger center disk and less of a drop in the rim. This cleared the calipers. Unfortunately, during the 1960s GM built both types of wheels and the early SSI wheels are the older style deep drop/small center design. Only the 1970-up SSIs will clear the factory 10.5" disks.

[jturkey69]

Joe, I found a disc brake kit with 500 miles on a 69 Camaro a guy is selling on Craigslist for 275...2" drop spindles, assembled with calipers and rotors, backing plates and hoses. The links above are dead, so for my 71 with power drum brakes, I only need a disc brake m/c and a prop valve for disc, but from/for what?
will the 2" drop be ok with the control arm shimming that it may need?

Thanks for the help.

Turkey

[joe_padavano]

Originally Posted by jturkey69

Joe, I found a disc brake kit with 500 miles on a 69 Camaro a guy is selling on Craigslist for 275...2" drop spindles, assembled with calipers and rotors, backing plates and hoses. The links above are dead, so for my 71 with power drum brakes, I only need a disc brake m/c and a prop valve for disc, but from/for what?
will the 2" drop be ok with the control arm shimming that it may need?

Thanks for the help.

Turkey

Be careful with the dropped spindles. The Camaro steering arms are different from those on the A-body cars. The stock steering arms bolt on, so you can swap them easily. If the aftermarket dropped spindles also use bolt-on arms, you're fine, just use your old ones. If the spindles have integral steering arms, they will not work.

[jturkey69]

The kit is from Classic Performance Products, otherwise I will also ask. Otherwise Im ok using my booster, and getting a new m/c and prop. valve? Should I buy new, or get one from a 67-70 disc brake car?

Thanks for the heads up, and the help!!

Turkey

[jturkey69]

Classic Performance Products web site says the camaro kit uses stock balljoints and steering arms...so does this mean it will work on my car?

[joe_padavano]

Originally Posted by jturkey69

Classic Performance Products web site says the camaro kit uses stock balljoints and steering arms...so does this mean it will work on my car?

Yes, so long as the steering arms bolt on, you can use your stock ones. Any Cutlass disk brake M/C will work fine. Easiest plumbing for the proportioning valve is to use an external one like the 67-70 cars.

[jturkey69]

ok, gotcha...Thanks!!!

[BIGJERR]

Originally Posted by jturkey69

Joe, I found a disc brake kit with 500 miles on a 69 Camaro a guy is selling on Craigslist for 275...2" drop spindles, assembled with calipers and rotors, backing plates and hoses. The links above are dead, so for my 71 with power drum brakes, I only need a disc brake m/c and a prop valve for disc, but from/for what?
will the 2" drop be ok with the control arm shimming that it may need?

Thanks for the help.

Turkey

Buy that camaro put it on Ebay and then take the profit and use the bolt on stuff!

[jturkey69]

I could do that, but I dont use paypal anymore...I may just buy the right stuff anyways...this way I can not have any mistakes. I just need to find the right one for a cheap price.

[#1CutlassSupreme]

Dang it! I wish I would have seen this post before Joe!

My 72' Supreme had factor disk in front and I just decided to spend the extra money and buy a complete upgrade to 4-wheel disk all the way around. The booster bolted right up, master cylinder fit well, and even the proportioning valve fit in the factory mount. There was a little work to get the rear drum backing off and since you've got to pull the axles, you may as well do new bearings while you got her opened up.

The rotors were a bit bigger than stock at 11" and even going up to SSIII JJ 15x7 Rally wheels, I still had issues with the calipers rubbing on the wheels in the back.

I fixed that issue by putting on some 1/2" spacers which gave me about 1/4" - 3/8" clearance between the wheel and the ear on the rear calipers.

Sorry to Hijack, but just some FYI for the guys looking to upgrade.

[jturkey69]

Its all good #1, I will take all the info I can get!