# 68 disc brake conversion



## Black68GTO (Dec 13, 2010)

My father just got a 68 GTO. Fully restored to like new condition with little issues here and there with a factory 68 400 in it but not the one that came in it. Anyway he wants Disc brakes all around. Who makes a good kit that fits easily and quickly. 

Im not a mechanic but i do work on a lot of cars for fun. I am a jeep guy so i can handle custom brake work and welding stuff up. 

I need to make sure i have a working E-brake in the rear discs.

Let me know whats out there.

Mason.


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## Black68GTO (Dec 13, 2010)

let me start with an easier question then. 

What years of the GTO are the same as the 68 as far as parts such as brakes.


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## sixeightGTO (Jan 25, 2010)

The first question is what size of wheels are you running? If you are running the stock fourteen inch wheels some disc kits can have fitment issues. I converted the front drums on my 1968 using a kit from Ames Performance. The Right Stuff is the company that put together the kit. I have stock fourteen inch Rally II's. I had to shave down the brackets to make it work with a fourteen inch Rally II. If you are used to working on Jeeps and welding than that is definitely a non issue. I was pleased with the kit Ames also sells a rear kit. You can definitely piece together a disc set up from other A-Body cars but I went with a kit for simplicity and the fact that I am doing a frame up on my car I liked the idea of replacing all of the hoses and lines since some were questionable.


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## geeteeohguy (Feb 2, 2008)

I would install GM '69-'72 spindles, calipers, and rotors. They're cheap, work excellent, and fit perfectly with no issues. I would leave the rear drum brakes alone: 75% of the car's braking is done by the front brakes, and the rear drums will lock up easily anyway....I think rear disc brakes are over rated. Plus, they have marginal emergency brake capabilities compared to a full rear drum brake. Helped a friend convert his '65 over to front discs, and the total cost (boneyard parts plus caliper kits) was $90. (This was a few years back, though!!)


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## Black68GTO (Dec 13, 2010)

When you say i should install 69-72 parts, does that mean that the spindles are a direct bolt on and than GM started using Disk brakes on there cars in 69?

Are the 69-72 gm brakes power? can they be power if i put in the power components?

If so this seems like a very basic autozone project for the front end at least. I realize that rear drums are ok but my father wants disks all around and he doesnt mind spending the money that goes along with it. 

below is a link to the car that we got. Picking it up on friday, im just really excited to get working on it.

Pontiac : GTO - eBay (item 270677416540 end time Dec-12-10 08:47:21 PST)


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## geeteeohguy (Feb 2, 2008)

GM started using disc brakes earlier than '69, but the '69-'72 brakes are single piston caliper, well engineered, zero-issues, commonly available brakes. They were used on millions of A-bodies. They are a direct bolt in, and will not affect alignment or steering angles at all. There is no difference at the axle between power and manual brakes. If you want to convert to power brakes, you simply need to add a power booster to your master cylinder. Have fun!!


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## BearGFR (Aug 25, 2008)

Black68GTO said:


> I need to make sure i have a working E-brake in the rear discs.


Looked at the Ebay listing --- not a bad looking car in the photos and it already has some good pieces on it.

I'm "in the process" on my 69. It had factory front disc brakes, but I'm replacing the entire system with Wilwood Dynalite Pro 4-piston on all 4 wheels. The rear brakes also have an internal drum "Explorer type" parking brake. I bought two "kits", one for each end of the car. They won't fit 14" wheels, 15" are required as a minimum. The calipers in the kits have 1/8" NPT (pipe) fittings in them. Adapters are needed to connect inverted double-flare lines (not included). Also not included are the parking brake cables. I got my cables from Lokar. Not included in the front kit are the hydraulic flex lines, plus if you want to run steel wheels you'll also need two hub "protectors" (also not included in the kit) to keep the wheels from scarring up those nice pretty aluminum hubs.

Wilwood recommends using an adjustable proportioning valve on the rear brakes.

For the rest of my system, I'm running a hydroboost system since my 461 only makes 12-13" of idle vacuum. Rather than buying an off-the-shelf hydroboost kit, I'm almost done with engineering my own system using a 69 Corvette master cylinder (new from NAPA) and a hydroboost for an 83 3/4 ton diesel pickup (rebuilt from NAPA) and custom hoses. It's going to come in at about half the cost of a complete kit.

Bear


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## Black68GTO (Dec 13, 2010)

the car has 15" crager ss wheels on it so i dont think i will have to deal with much as far as a fitting issues since im going to stay with a fairly basic set up. 

I could get away with just rebuilding the stock rear drums and being happy with that but my father wants disk, hes paying, and it will probably be easier to put disk brakes on than to rebuilt drum brakes.

i hate working on drum brakes.


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## BearGFR (Aug 25, 2008)

Black68GTO said:


> the car has 15" crager ss wheels on it so i dont think i will have to deal with much as far as a fitting issues since im going to stay with a fairly basic set up.
> 
> I could get away with just rebuilding the stock rear drums and being happy with that but my father wants disk, hes paying, and it will probably be easier to put disk brakes on than to rebuilt drum brakes.
> 
> i hate working on drum brakes.


It looks like Wilwood might have made a few minor changes since I bought mine, about 8 months ago, but I think these are the fronts I'm using, and I think these are the rears. This ought to be at least close enough to give you an idea about what's in the kits. I'm running a Moser 9" Ford rear axle, so you'd need whatever fits the axle your car has.

To recap, in addition to what came in the brake kits I had to buy:
Fittings to connect the rear brake lines (flare to 1/8" NPT)
Flex hoses for the front
Parking brake cable kit (Lokar)
Hub protectors for the front (I'm running steel wheels)
Master cylinder
Adjustable proportioning valve​
If you decide to use something like these, by all means shop around on the "inter-tubes" for deals. I got mine quite a bit cheaper by doing that.

Bear


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## OrbitOrange (Jul 5, 2010)

If intrested I have a factory front disc brake set up from a 1970 chevelle Id sell ya pretty cheap. I was going to use it and found another frame that Im using that already had disc brakes on it so I have no use for it.


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## Black68GTO (Dec 13, 2010)

BearGFR So this front set up bolts directly onto the stock front spindle? If so this seems like a very easy setup and what i would probably go with. I was seeing other setups that required spindles and werent as nice as wilwoods for over 1K.

Also any recomendation on where to find the (flare to 1/8" NPT) when i was doing some research on building a Dana 70 for my jeep (that i never finished) i was seeing that size item was very difficult to find.


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## BearGFR (Aug 25, 2008)

Black68GTO said:


> BearGFR So this front set up bolts directly onto the stock front spindle? If so this seems like a very easy setup and what i would probably go with. I was seeing other setups that required spindles and werent as nice as wilwoods for over 1K.
> 
> Also any recomendation on where to find the (flare to 1/8" NPT) when i was doing some research on building a Dana 70 for my jeep (that i never finished) i was seeing that size item was very difficult to find.


Yep, they bolted right up to my factory spindles. Now, bear in mind my car had factory front disc already - I don't know if the spindles for drum brake cars are different. Even if so I suspect Willwood might make a bolt on kit for those as well.

The fittings aren't hard to find. In my area both Autozone and OReilly have a plethora of them in the bins, you just have to dig sometimes. It was a little irritating to me to think that I'd bought a "kit" but still had to round up other pieces to actually install it, and of course I made that discovery "in the middle of the night" when I was up late working on the car, after all the stores had closed... 

1/8" NPT is also called 1/8" pipe tap.

You can also get the pieces from places like Summit, for example here are the "extras" I had to buy to actually install the brake system (not including the hydraulics associated with the master cylinder, which I'm still working on)
Parking Brake Cables
Brake Line Fittings
Flex lines
Hub Shields


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## Black68GTO (Dec 13, 2010)

In doing a little more research i am thinking that i will need new spindles to accept the front disc brakes.

Any opinions on this kit? Right Stuff Detailing AFXDC41CSX - Right Stuff Detailing Power 4 Wheel Disc Brake Conversions - Application - SummitRacing.com


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## BearGFR (Aug 25, 2008)

Black68GTO said:


> In doing a little more research i am thinking that i will need new spindles to accept the front disc brakes.
> 
> Any opinions on this kit? Right Stuff Detailing AFXDC41CSX - Right Stuff Detailing Power 4 Wheel Disc Brake Conversions - Application - SummitRacing.com


I did a little poking around and it turns out that drum brake front spindles are different from disc, but they can be modified to work. Here's the "meat" from a post that talks about it:
_"I've done this modification several times. I found the amount to cut off different on all the spindles. I attached the caliper bracket to the lower mount, snug but not tight and then rotated the bracket up until it touched the upper pivot bolt boss and scribed a line. I used a hacksaw to remove the majority of the boss and a Bridgeport mill to machine them flat. The flats on the backside of the steering arm mounts are plumb to the axle centerline and parallel to the surface of the boss. Oh, BTW, this only pertains to 69 and later spindles. You can modify earlier spindles, it's just a little more work._​
The thread is located here

Again, this modification applies to factory-style disc brake calipers. Wilwood makes front disc kits for both disc-type spindles and drum-type spindles, so all you have to do is get the kit that's right for what you have. Here's a link to Wilwood's product selection page for 69 GTO's. Notice there's a button that says "Select your OE model option" where you choose which type of spindles you have.

If Wilwood has them, other manufacturers probably do too.

Bear


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## Black68GTO (Dec 13, 2010)

ok so i found out the rear end on this car is a Dana S60 and not a stock one. The motor is a built 400 with 3x2 carbs and puts out about 400 horse. so i think im looking at the below set up then gotta figure out what to do with the rear.

Summit Racing SUM-BK1201 - Summit Racing® Complete Drum-to-Disc Brake Conversion Kits - Overview - SummitRacing.com


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## BearGFR (Aug 25, 2008)

Black68GTO said:


> ok so i found out the rear end on this car is a Dana S60 and not a stock one. The motor is a built 400 with 3x2 carbs and puts out about 400 horse. so i think im looking at the below set up then gotta figure out what to do with the rear.
> 
> Summit Racing SUM-BK1201 - Summit Racing® Complete Drum-to-Disc Brake Conversion Kits - Overview - SummitRacing.com


That same web site I sent you in the previous post can help configure kits for different rear axles also. You may need to take some measurements but the site has instructions. It worked for me, and I'm running a Moser 9" Ford rear in my 69.

Bear


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## johnflag (Dec 9, 2017)

OrbitOrange said:


> If intrested I have a factory front disc brake set up from a 1970 chevelle Id sell ya pretty cheap. I was going to use it and found another frame that Im using that already had disc brakes on it so I have no use for it.


still have the chevelle disc brake set up,if so I am interested!


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## Mike E (Jun 9, 2018)

Hello, I bought a 68 GTO Convertible, numbers matching. I'm not happy with the power drum brakes on the car at all. Two questions....first, will a drum to disc conversion lower the value? Just wondering if this ruins the originality of the vehicle. Second, should I just get the front brakes converted? Im told that a rear conversion wont make much difference and will definitely be less expensive. I appreciate all of your thoughts. Thanks!


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## TxGTO69 (Dec 2, 2020)

BearGFR said:


> Yep, they bolted right up to my factory spindles. Now, bear in mind my car had factory front disc already - I don't know if the spindles for drum brake cars are different. Even if so I suspect Willwood might make a bolt on kit for those as well.
> 
> The fittings aren't hard to find. In my area both Autozone and OReilly have a plethora of them in the bins, you just have to dig sometimes. It was a little irritating to me to think that I'd bought a "kit" but still had to round up other pieces to actually install it, and of course I made that discovery "in the middle of the night" when I was up late working on the car, after all the stores had closed...
> 
> ...


Hey Bear
I know this was 11 years ago, but do you remember if you had to drill and tap your 69 GTO spindles for you wilwood brake kit? I see in the kit some spindles may require the upper bolt hole to be enlarged to a 5/8" fine thread hole. No big deal, it would just be good to know ahead of time so I can have to tools on hand. I have tried searching that bolt size for 69 to no avail, but something is telling me it already is 5/8"

Thanks
Kris


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## O52 (Jan 27, 2019)

There are differences in the drum brake spindles, not sure about the disc spindles. The photo below shows my stock 68 Drum brake spindle and a drum spindle bought from a junkyard. Supposedly it was from a Chevelle, year unknown.


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## TxGTO69 (Dec 2, 2020)

O52 said:


> There are differences in the drum brake spindles, not sure about the disc spindles. The photo below shows my stock 68 Drum brake spindle and a drum spindle bought from a junkyard. Supposedly it was from a Chevelle, year unknown.
> 
> View attachment 140310


I am sure the there are. I was asking Bear specifically, because like my car his is a 69 factory disc brake car and I was hoping he may recall if his factory disc spindles had to be drilled/taped to accommodate the wilwood kit. I should have clarified my question further. Thank you for the information.


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## TxGTO69 (Dec 2, 2020)

Sorry, didnt mean to reply twice and I dont see how to delete this post.


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## 1969 tempest custom s (Sep 9, 2020)

another consideration is to put a set of rear drums on the axle from a 76 or 77 a body colonnade. they are 11 inch diameter rather than 9.5. and you can upgrade them further with drums from a colonnade wagon. i am doing that right now. actually the 11 inch drum backing plate is the hard part to find. the rest is easily available from rock auto. use your a body park brake cables because the colonnade cables are too short. very easy upgrade and compatable with an origional factory disc brake set up


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