Disc Brake Conversion Done?

[wxman1]

Well...I've finished my front axle conversion to disc brakes on my 69 C-10 p/u. I've bled the system and so far there aren't any leaks. But...there are a couple of things. I don't really get the nose diving performance from the discs up front that I thought I would. Also...the pedal sits about 5 1/4 inches above the floorboard which is normal height for this truck. When fully depressed it goes down to 3 1/4 inches above the floorboard. At that point it becomes very hard. While the system easily stops the truck...I don't think I can lock up the wheels. Should I be able to do that? Is this an adjustment issue on the power booster rod?

Also...this system has an MBM PV2 proportioning valve. I ran one line (1/4") to the rear and and 2 lines (3/16') to the front caliphers. Thinking I should get more dive on the nose under hard braking I researched this valve. Vendor I bought the valve from says there is no adjustment between back and front.
Anybody know anything different?

Jim

[Longhorn 70]

Jim,

I just did one too. No nose dive for me but my front end is stiff. It does stop a lot better. I also get a chirp from one of the rear brakes from weight transfer. BTW mine is a stock C20. I used the stock master cylinder with proportioning valve.
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[GoaterAz]

What disc brake conversion did you go with?

[wxman1]

The conversion kit was from McGaugheys sold by Srn Ky Classics. Bought the
spindles also so that I wouldn't have problems with tie rods. Also...the stock
rallys that came with the truck work ok with the conversion with no clearance
issues.

Jim
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[lolife99]

You could always add an adjustable proportioning valve in the rear line.
This way you can dial in the amount of fluid you send to the front brakes and limit the amount of fluid you send to the rear brakes.

[ZUBZ]

Guys I have 2 questions as I am in the process of ordering the same disc brake kit. Do I have to order a master cylinder / booster and did you order the 12inch disc brake kit to be able to still use the stock steelies? My stock steelies are 16inch.

[Classic Heartbeat]

I believe the kit is 11" brakes. If you are talking about using the stock wheels from a 1970 or older 2 wheel drive, you can't use them. The inside of the wheel will hit the caliper. You need to use 71 or newer 4X4 6 lug wheels (steelies) in order for the kit to work. WES

[ZUBZ]

Originally Posted by Classic Heartbeat

I believe the kit is 11" brakes. If you are talking about using the stock wheels from a 1970 or older 2 wheel drive, you can't use them. The inside of the wheel will hit the caliper. You need to use 71 or newer 4X4 6 lug wheels (steelies) in order for the kit to work. WES

Wes the issue I have is these wheels are hard to come by down here and all I have is the stock 16inch steelies. How come guys are running these kits with 15inch rallies, are they not steelies?

[knomadd]

Originally Posted by wxman1

...While the system easily stops the truck...I don't think I can lock up the wheels. Should I be able to do that?
Also...this system has an MBM PV2 proportioning valve. I ran one line (1/4") to the rear and and 2 lines (3/16') to the front caliphers. Thinking I should get more dive on the nose under hard braking I researched this valve. Vendor I bought the valve from says there is no adjustment between back and front.
Anybody know anything different?

Jim

Jim, a large amount of nose dive should only be happening if your springs and shocks are not able to handle the weight of the truck (wearing out, or under sized). You will naturally have some nose dive due to weight transfer, but if your springs and shocks are good, there shouldn't be a lot of nose dive. There's probably a little more too it, but I'm not a suspension guru, so someone else can chime in if need be.

As for locking your brakes, if you're valve is properly adjusted for the application (most are), you shouldn't lock up the brakes unless you stomp on the pedal HARD (hold on tight if you try this).

I did a front disc conversion on my GTO and had several issues with the brakes not stopping like i thought they should. It has stock drums in the rear and I could lock them with the old drum/drum setup, but not the disc/drum setup. I installed an adjustable proportioning valve between the disc/drum valve and the rear brakes, but even with it completely open I couldn't lock them up, no matter how hard I stood on the pedal. I went through two boosters and two master cylinders trying to fix it. It turned out the vacuum booster needed around 18-22" of vacuum. I had 18", but that wasn't enough. I installed an electric vacuum pump that shook the $#!+ out of the car and didn't do a d@mn bit of good. I wound up switching to a Hydratech booster and it's night and day difference. My GTO now stops like a modern car (a big one, but still a whole lot better than before). I've got the same booster to install in the C10 as my factory discs don't stop the truck like I need around Houston (for my driving style and most others around me ).

Hope this helps.

[wxman1]

In my conversion, I decided to get a disc brake master cylinder(with the larger
front reservoir) and continue to use my booster from the power drum brake
system that was on the truck. Not sure if that was a mistake or not?

As far as the wheel clearance goes, these are 6 lug 15 inch rallys and I've
not had any clearance issues. See attached pic.

Jim

[Classic Heartbeat]

Wes the issue I have is these wheels are hard to come by down here and all I have is the stock 16inch steelies. How come guys are running these kits with 15inch rallies, are they not steelies?

The problem is the design of the back of the wheel. GM changed the design in 1971 to accomidate the rotors and calipers. Here are a couple of wheel profiles to help you tell if what you have will work. You may be able to do it with the 16" wheels, here in the states most of these trucks came stock with 15". WES