The Stovebolt Site Forums The Shop Area Driveline Disc brakes

Hi, have a 49 1/2 ton chev pickup with original drum brakes, have already converted to dual master cylinder. Could i convert to front Disc without adding a booster?

You can, but adding one would be highly recommended. Disk brakes are not self energizing, and do reqire much more pedal effort when used without a booster.

Why would you not want a booster. If you have the vacuum go for it.

Check this out.
http://s729.photobucket.com/albums/...withLokarShifterBracket.jpg&newest=1

The reason not to use a booster is the difficulty I've read others have in keeping the stock clutch pedal with any of the kits.

My own experience is that you can get away just fine with a non-boosted disk brake system, but if adding a booster were cheap and simple I'd probably go ahead and do it...

I know about the difficulty with the clutch. How much trouble is it to convert to a Hydraulic clutch?

I've wondered this myself about using non-boosted disks. I have converted my '47 to a dual master but would eventually like to convert to disks. This obviously puts the master further back. My truck is lowered so the finger check for fluid level could only be done with the entire truck jacked up on all 4 corners. Of course a new check hole could be drilled. So...any more thoughts on boosted vs non-boosted disks?

With respect to the "finger check" I'd say, how often do you check the break fluid. Realistically most guys, unless they haven't anything else to do, don’t need to check more than a couple of times a year. That is considering your system is tight.

On my '49 I made a bracket to mount the booster/mastercylinder [censored]. back under the seat , then I have a small "bump" in floor to allow the booster to go up a little higher . (I am using a large booster - its what I had laying around and was free) I also have a small door for access to the cylinder lid. I fab'ed a linkage rod to connect the original brake pedal arm too the booster . Works Great ! On my '38 I ran non-assisted disc and it stopped fine , I made my own brake arm though and played with the leaverage/arm lenths to get a good "feel".

On my 47 I've got discs on front '54 drums in back, stock master cyl, and while I know I need the dual system it's way better than stock for now. I had to use the residual valves but it works great. I've been wanting to check with Buffalo Ent for a bracket set up. That guys has all the tricks for this kind of mod.

On my '54 burb I had no trouble with interference with the clutch mechanism and the booster. I used the Performance Online kit. The booster is smaller diameter than the CPP kit.

http://i232.photobucket.com/albums/ee12/cletis_photos/1954%20GMC%20Suburban/brakes/010.jpg

There you go!

261fun.... there is a lot of good information on this thread for you. These more experienced guys are making a lot of great points on your original question for you to consider.

I recently went through the same delema as you.

I have a 50 ½ ton and I installed the Performance Online front disc brake kit on my truck. I went without the booster for now. My truck is still on jack stands so I won’t know if I regret not installing the booster.

The pic cleatis posted is great, I think that set up is on a suburban.

On my 50 pickup that booster that cleatis is showing would not fit without modification of the trucks original trans crossmenber. The whole set up would be too long. If I had gone with the booster I would have had to remove the original trans cross member and purchase a aftermarket one and move it to the rear. This may not be the case for your year truck but it is something you can look into.

I think you said you are set up for drum/drum right now. Your current dual master cylinder may not work with a disc/drum system. You may have to purchase a new dual master cylinder or at least add a prop valve. If you look at cleatis picture you will see the prop valve mounted right under the master cylinder.

The brake and clutch fit perfectly on POL kit I bought.

You may have to run new brake lines, at least to the front.

You may find out while you’re doing this work that your kingpins need replacement.

You may have to add residual check valves in the your brake lines
Your current wheels probably will not fit the front disc brakes. Depending on what you’re running on. The wheels I had on my truck did not fit the front brakes.



Picture of my wheels that do not fit after disc brake upgrade



There is a lot to consider if you’re going to do the upgrade. Weather you go with a booster or not there will be some head bumping and head scratching work involved. But when you’re done and your knuckles heal I’m sure your be satisfied and your be able to stop your truck better when that little honda cuts you off.

JiMerit how much work was it to convert the rear axle to 54 (Bendix I presume) drums/brakes? Stock axle?

By the way, I love the way the Suburban stops with power disc brakes.

Thanks for all the info guys, one more question, where would you recommend for a disc brake upgrade system? CPP,Performance on line, etc ???

Question: are you planing on upgrading the rearend. That 261 will be "pulling on the bit" with the original rearend. There are a couple (maybe more) of rears that would allow a drum to disc conversion. That would be GM 10 and 12 bolts. With that conversion you can buy 2002 GM disc brakes that will bolt on.
I bought the CPP dual master cylinder and booster and am very happy with it.

P.O.L. kit on 1950 chevy 3100

Using asbestos pads and shoes will make you think you added a booster. Asbestos friction is all over ebay and well connected brake suppliers can still get it. It is like R-12 refrigerant, illegal to manufacture but legal to buy, sell and own. It has a vastly higher friction coefficient that "organic" friction and is also easy on drums and rotors.

How do I know this. My '36 Chevy pickup was restored in the early 70s when asbestos was all there was. It stops great with an all original brake system except for silicone fluid.

Also I have a street rod, a SBC Chevy powered '32 Ford roadster. It has a Ford 8 inch rear end with stock 10" x 2" drum brakes and GM "Metric" discs in front, non-boosted. With available "organic" friction that thing would not stop. Now, with asbestos friction it stops great!

FYI,

There is a vendor that has a rear disk conversion for the original pre-63 rear axle. I do not remember who it is, but they should not be hard to find.

Asbestos brake linings are illegal in the US. Have been fior over 30 yearsAny asbestos brake linings that you are going to find are going to be chap Chinese junk, and is illegal to import into the US as well.

Bill, I may be wrong, I often am. The way this asbestos clutch and brake issue was explained to me is that what remains of old stock can be used but it is not legal to manufacture any more of the stuff. It's like R-12 refrigerant. That stuff is no longer being made in most countries but it is still "reclaimed" from wrecked vehicles. Anyone with a mobile AC license can buy R-12. I got one of those licenses by taking a 2 hour class where they teach the answers to a test and then they give you the test that you're allowed to take as many times as is required to pass it.

I have a '36 Chevy pickup so I often look on ebay for anything related to my truck. Old stock brake linings are on there all the time and occasionally shoes are there as well. Since the same brake shoes fit 1936-50 I thought that readers of this forum might find it interesting that the highly effective asbestos friction is available.

The asbestos shoes and pads I bought off ebay came in the original very faded boxes so they looked like old stock, not new parts from China. The best thing is how well they work.

When I put disk brakes on my '49 half-ton back in the 80's, I used a Nova/Camaro disk/drum master cylinder.

The '75 factory service manual lists 2 master cylinder bore sizes for that application, 1.125" for power brakes and 1.000" for manual brakes.

I used a manual master cylinder like this one Non-Power master cylinder on my truck.

To see how much of a difference there is between the two cylinders I did this calculation.

Area of 1.125" circle = .995 sq in
Area of 1.000" circle = .785 sq in

Pedal force of 50 lbs times mechanical advantage of the pedal (7) -> 50x7 = 350 lbs.

Power cylinder: 350 lbs / .995 sq in = 352 lbs/sq in line pressure

Manual cylinder: 350 lbs / .785 sq. in. = 446 lbs/sqin line pressure

446/352 x 100 = 126%

Bottom line, the smaller bore gives you a 26% increase in brake pressure for the same pedal push.

OlBlue, another option is the 21mm (0.819")master cylinder that was used on the 1985 T-bird and probably other Fords. An added benefit is that it is aluminum so there will never be any rust problems.

I have one of those without a booster on my '32 Ford roadster street rod and in combination with asbestos friction it stops "on a dime".

Ok, NOS parts I can see still being able to buy, but why? There's much better available in modern materials. Especially with a disk conversion that's using parts from later model vehicles that never used asbestos in the first place. I personally prefer Wagner, especially the Thermo Quiet and Severe Duty SUV/Truck friction. Bendix and the AZ C-Max brake friction is very good, too.

Bill, when I found that my newly constructed street rod roadster was plenty fast but wouldn't stop I went to a local brake supplier that is now second generation, managed by the sons of the founder. I told them of the problem I was having with stock rear 10" drum brakes on a Ford 8" rear end and a front brake setup using Aspen/Volare 11" rotors and GM metric calipers adapted to an early Ford beam axle. A asked them if they thought ceramic or metalic pads and shoes were the answer.

These are really honest guys, something pretty rare in today's corporate economic sewer, and rather than selling me some expensive friction they said "Before trying the pricey ceramic friction or the metalic friction that will chew up your drums and rotors, lets try some old school, inexpensive asbestos. A few warehouses still have a very few part numbers left. Let us see if anybody still has your parts. If that doesn't solve the problem, we'll try something else."

It took a while, but they got the asbestos for me. That was 10,000 miles and 5 years ago. After I found out how well it works I got some more off ebay for my roadster, for a friend's roadster and for my El Camino that has the same metric front brakes as my roadster.

Anyway, that's how I tried asbestos after not using it for about 25 years.

For what it's worth, I also have R-12 refrigerant that I bought before the price spiked that I use in my '71 Dodge van and my '78 El Camino. That avoids having to convert to R-134 to keep those old trucks shooting icicles.

I guess I'm just old school and working hard to stay that way. To each his own, huh?

I did on a 1950 GMC with a Classic Performance Parts kit. Add a proportioning valve to the rear and it works great without the booster.

DO NOT patronize CPP. I bought their kit and it was a total PITA to install. The installation "instructions" are vague to the point where we had to tear the whole thing down twice to get it right. Parts were defective and customer service is non-existent.

I wrote them a long letter detailing my complaints and offering simple corrections to their instructions and never so much as got the courtesy of a response.

If you want to patronize a company that sells defective products with a screw you attitude please do buy from CPP. Personally I'd take my money elsewhere.

EDIT: I found the letter I wrote them and here it is:

My mechanic recently completed the installation of your Disk Brake Conversion #4759DBK-6 on my 1951 Chevrolet 1/2 ton pick up. I am writing with a couple suggestions to improve your instruction sheet, and to complain about the problems we encountered with some parts.

I would suggest that you make the following two revisions to your instructions:
1. Indicate the correct position of the offset of the Caliper Mounting Bracket. The instructions make no mention of this and if you guess wrong you have to remove the hub to correct the problem.
2. You should mention that the Steering Link spacers should be removed. There is no mention of this and again, if you do not do this you must remove the hub to correct the problem.

The following is a list of problems we experienced with the parts:
1. The aluminum spacer holes did not align with the hub from the front brakes causing misalignment and runout in the front wheels. A larger hole should be considered.
2. The brake actuator rod on the Power Brake Booster #4754BB is too long. I must be cut and rethreaded to fit.
3. The Master Cylinder bracket is not correct for this vehicle. It hits the cross member and must be modified to mount securely.
4. Both the master cylinder and proportioning valve leaked around the plugs that were already installed.
5. Both rotors were warped and had to be turned. You should suggest to turn the rotor assembly after it is assembled to allow for smooth braking.

I feel that the omissions in the Instructions, although frustrating, do not affect the quality of the conversion. However the defects in the master cylinder, proportioning valve and rotors, as well as the other problems encountered do not speak very highly of the quality of this kit or your quality control standards.

Furthermore these defects added almost $200 to the cost of installation by a 26 year Master ASE Certified Technician with 33 years race car and street rod building experience.

Once installed the braking is dramatically improved but the problems one can expect to encounter would not make your products something that I would recommend. 

Hopefully your customer service will redeem you and therefore your comments are anticipated.

Woody,

I too bought CPP's 6 lug kit for my 54. I spent many hours fixing their mess. While there is nothing structurally wrong with their kit, if it is installed by someone without the skill to fix the mess or someone that thinks that just because it is provided by a "professional supplier" it will perform great, I am sure poor performance will be the results. This would manifest itself in short pad life and less than optumum braking.

The problems I encountered are documented in my build pictures.

I was also shipped the wrong caliper brackets. They sent me passenger car brackets. When I called their support, they as much as told me I did not know what I was doing and that they do not make shipping errors.

I am not saying do not buy CPP, just be aware of the potential problems.

In hind sight I would have purchased a bracket kit and bought the rest of the parts locally. I did not know a bracket kit was available at the time.

I hope this is not a hijack of this thread, lots of great information here. Quick question, when mounting the booster under the truck, it seems that every time you hit the brakes, the system takes a big gulp of whatever dirty air that is under the truck at the time. Is this not a problem? I had been considering such a system, and was trying to figure how to get clean air to the booster. Any ideas? Is this a non-problem?

Mark

If you are referring to the brake booster, it doesn't suck in air it receives vacuum from the engine.

I have boosted power brakes with disc on my 54 and i put a remote reservoir on the fire wall. i got a billet one for looks instead of plastic. ron