69 GTO Rear Drum to Disc Brake Conversion Kit - Pontiac GTO Forum
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post #1 of 10 (permalink) Old 01-12-2012, 08:19 AM Thread Starter
 
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69 GTO Rear Drum to Disc Brake Conversion Kit

I have a 69 GTO with the stock rear drum brakes. I would like to convert these to disc brakes. I have been looking through the GTO parts cataloges and have found several drum to disc conversion kits. However, I am not sure what I need. Several of the kits include new master cylinders and boosters.

Do I need a new master cylinder specially made for 4 wheel disc brakes or will my existing master cylinder work fine. There is nothing wrong with my master cylinder or booster and I have front disc brakes that work fine.

If someone could reccommend a rear drum to disc conversion kit that works with the stock parking break cable that would be great. Preferably something ready to just bolt on and go. I want to use all my existing brake lines if that is possible. I have never done brake
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post #2 of 10 (permalink) Old 01-12-2012, 08:58 AM
 
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Try RIGHT STUFF. They advertize here. My friend just used thier product and is happy with the results. You MIGHT need a different , or adjustable proportioning valve...They will know.



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post #3 of 10 (permalink) Old 01-12-2012, 09:04 AM
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The front brakes apply 75% of the stopping power for these cars. IMO, rear disc brakes on a mainly street driven car are overkill and over rated. Not necessary, and expensive. That said, a lot of people like them, and they are superior to drums in stopping power, (though inferior to drums as an emergency/parking brake). Several of the gents on this forum have installed them, and have had good to excellent results...they can help you with your quest. Me, I'd spend the money on something else.
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post #4 of 10 (permalink) Old 01-12-2012, 10:26 AM
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Originally Posted by jtwoods4 View Post
I have a 69 GTO ...

... Do I need a new master cylinder specially made for 4 wheel disc brakes or will my existing master cylinder work fine. There is nothing wrong with my master cylinder or booster and I have front disc brakes that work fine.

If someone could reccommend a rear drum to disc conversion kit that works with the stock parking break cable that would be great. Preferably something ready to just bolt on and go. I want to use all my existing brake lines if that is possible. I have never done brake
I can only talk about what I did on my 69, which was also a factory front disc car. I used Wilwood disc (Dynalite Pro - 12", 4-piston) on all 4 wheels. The rear brakes have the internal "Explorer style" drum parking brake. The attachment points for the cables to the parking brakes are very different from factory. It MIGHT be possible to modify the factory stub-cables to work, I looked at that and decided it would be easier to just buy a Lokar 'universal' cable kit and use that. I am using the factory style brake lines, but did need some fitting adapters because the calipers have 1/8" NPT (pipe tap) connections instead of reverse flares like the brake lines have.

Going from drum to disc, your master cylinder will be ok but you'll need to bypass the original brake hold-off valve (mounted in-line just below the master cylinder - some folks increctly call this the factory "proportioning valve" but for 69, that's not what it actually was) and install an adjustable proportioning valve in it's place for the rear circuit. This is because the calipers need different pressure levels from drums to work properly, and you'll want the adjustability in order to be able to dial in the correct front/rear balance.

Bear

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post #5 of 10 (permalink) Old 02-10-2012, 10:40 PM Thread Starter
 
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Baer, I found the brake hold off valve mounted to the frame a few feet below the master cylinder. I will remove this and replace with the correct proportioning valve. I looked at my master cylinder and it has 2 resevoirs. The front one is much larger than the back one. Is this ok?
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post #6 of 10 (permalink) Old 02-10-2012, 10:57 PM
 
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You could go to a Corvette master. Since they were four wheel disc, the cylinder and piston size will be correct. They look just like the factory GTO body master cylinder and are a direct bolt on. They're also no more expensive than the factory GTO master.

Just a thought...

Chuck

When the only tool in your toolbox is a hammer, you tend to see every problem as a nail.
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post #7 of 10 (permalink) Old 02-10-2012, 11:02 PM Thread Starter
 
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I dont want to go through the trouble of changing the master cylinder unless I have to. Baer knows his stuff and he thinks my master cylinder will work fine. This weekend I finally have time to work on the car so I want to maximize my time.... Thoughts????
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post #8 of 10 (permalink) Old 02-11-2012, 09:04 AM
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You could go to a Corvette master. Since they were four wheel disc, the cylinder and piston size will be correct. They look just like the factory GTO body master cylinder and are a direct bolt on. They're also no more expensive than the factory GTO master.

Just a thought...

Chuck
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post #9 of 10 (permalink) Old 02-11-2012, 09:42 AM Thread Starter
 
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Ok, picking up a 69 Corvette master cylinder from NAPA today. Here is the link:
NAPA AUTO PARTS)
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post #10 of 10 (permalink) Old 02-11-2012, 04:55 PM
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I used a 69 Vette mc on the Beast, myself

It was literally "plug and play" --- bolted right up and I didn't have to change a thing.

Bear

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Last edited by BearGFR; 02-12-2012 at 09:31 AM.
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