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Early CJ Drilled 11" Drums
By tommy b
This writeup describes how I changed the 9 inch diameter front drum brakes on my 1956 CJ5 to 11 inch drum brakes. In addition to swapping out the brakes, I also drilled the brake surface of the drums.
If you're wondering what benefit drilling the drums has this article on CH Topping & Co. does a good job of explaining.
The first question people ask is about water and dust. If you've driven a drum brake equipped car through water you know braking is non-existent. With holes in the drums, centrifugal force not only evacuates dust, but water immediately as well. But the main benefit is the fact that when drums are vented properly, so as to eliminate balance and material integrity problems, they virtually eliminate fade, which is.the primary reason discs replaced brakes while racing at the dry lakes. He figured drums in the first place. Gasses are vented as well, as the holes create what amounts to a venturi effect, venting gases created by compression of air between the shoes and drum that would otherwise be trapped in a stock, unvented drum, hindering braking efficiency. This also holds true with disc brakes (believe it or not), so venting is beneficial here, too.
The first task was to see what 11" brakes would fit. Somewhere I heard that the 11" brakes from a 1972 CJ5 would work. I checked a Hollander manual at a junkyard and found the following drum brakes interchanged with 72 CJ5 brakes:
- 72-73 CJ, DJ series drum only, front
- 72-73 CJ, DJ series, rear
- 72-73 Jeepster, drum only, front
- 72-73 Station Wagon, drum only, front
- 72-73 Station Wagon, rear
- 72-73 Truck, 11" rear
- 74 CJ series, welded, rear
To make the conversion I needed the brake backing plate with all the hardware. (wheel cylinders, springs, cable adjusters, etc.), and drums. I pulled mine off a 72 Wagoneer. One nice thing about these particular brakes is that they had star wheel adjusters and a self adjusting cable setup on all four wheels.
No more fooling with those tiny little cam adjusters that were originally on the 56. I was lucky with the drum removal. All four came off by hand, no puller required.
In order to get the backing plates off the Wagoneer, I had to remove the hubs in the front, and, since I planned to convert the rear brakes in the future, the axles in the rear. The tools I used on the front were:
- Allen wrench to remove the Warn manual locking hubs
- External snap ring pliers for the snap ring on the end of the front axle
- Hammer and chisel (or screwdriver) to flatten the tab on the lock plate
- 2 1/8" socket to remove the wheel bearing adjusting and lock nuts
- 9/16", 3/8" drive deepwell socket and ratchet to remove the six bolts holding the backing plate to the hub.
The tools used on the rear were:
- 9/16", 3/8" drive deepwell socket and ratchet to remove the bolts holding the backing plate to the axle housing
- 5# slide hammer with an axle adapter
One axle came off easily when I pulled it by hand, I had to use the puller on the other. Another methods
of pulling the axles is to mount the drum backwards on the studs, screw the bolts on about 4 or 5 threads and use the drum as a puller. I first saw this in a 3/11/05 post by DanStew.
After getting the parts home, the first step was to remove all the rust, grease, and dirt from the parts.
I used a 4" sidegrinder and a die grinder with wire wheels to clean them up. Then I took the drums to the local Big O Tire store to have them measured to make sure there was enough meat on them to be able to turn. The new drum diameter was 11.00". The max diameter was 11.090". The largest diameter on mine was 11.025". After measuring them, they turned a clean brake surface on them. While there, I asked whether they would prefer to turn them before or after I drilled them as I had heard that some shops don't like to turn drums that had been drilled. What I found about turning predrilled rotors is that the instructions that come with drilled rotors say, "Don't turn them - replace them". I got to thinking about it and a possible problem I see with turning predrilled rotors (or drums) is that each time the toolbit hits the edge of a hole it gets jarred. If the frequency of these jarrings approaches the critical frequency of the drum or tool bit, then the tool bit is going to chatter and give a rough surface to the drum. So, I had the drums turned before I drilled them.
I made a jig to hold the drums for drilling, using a suggestion by Lynn in a post dated 12/02/05.
It is simply two 2 x 4's, 12" long, mounted on a 12" x 12" piece of " plywood. The holes are drilled 1" deep in 4 places to hold two 11" lengths of " pipe. The holes are1 1/8" diameter. x 1" deep. When setting up the jig, I marked a line on the top of the plywood parallel with and centered between the two pipes. This marks the vertical centerline of the drums, where I wanted to drill. As a suggestion, I would make the plywood 15" long and the pipes 14" long. This will allow you to slide the drum assembly sideways enough to drill all six rows of holes without having to realign the jig so that you are drilling perpendicular to the surface of the drum.
For drilling, I used a 1/8" drill bit running at about 2600 RPM to get the proper drilling speed for cast iron. I made a gauge and marked it at 3/8" (in the bottom of the groove), 1 3/16" and 1 15/16" from the drum surface.
Since the circumference of the drum at the bottom of the groove was just over 36" I marked a narrow strip of steel at 1/2" intervals, held this strip in the bottom of the groove, and made marks around the rim at 1/2" spaces. Holding the jig against the flat side of the drum, I marked the first hole at the 3/8" line. Then I moved the jig to the second 1/2" point and marked the hole at the 1 3/16" line, moved it to the third " point and marked the hole at the 1 15/16" line. I kept repeating this pattern which gave me 24 holes in each line or 72 holes in each drum.
After drilling all the holes, I mounted a drum on the hub and marked where the rows of holes were with relation to the shoes.
They seemed to be spread evenly across the width of the shoe.
After drilling, I painted the outside of the drums with Rustoleum satin black, using a rattle can. A note of caution: After painting, I had to drill out a few holes that had become plugged with paint. Maybe drilling 3/16" holes instead of 1/8" would eliminate that problem. I also wonder if 1/8" holes will tend to pack with mud easier. Well, if they do, I can always drill them out to 3/16" then.
The next step was to clean up the backing plates with a wire brush, paint them with the same Rustoleum paint, Hone out the wheel cylinders, install kits, and assemble the components onto the backing plates.
I then cleaned and painted the front hubs, repacked the wheel bearings, and replaced the inner hub seal. I also cleaned and lube the hub lockers.
In order to keep the wheel cylinders at the highest point (after dropping down from the master cylinder) to make bleeding easier, I made two brackets to hold the end of the brake hoses where they connect to the hard brake tubing on the front axle.
These brackets are held in place by the outer spring U-bolts as I didn't want to weld on the axle housing.
Since the 72 Waggy hoses were too long (15"), I bought two hoses that fit 1958 to 1965 and 1971 to 1973 DJ series Jeeps. These hoses are 12" overall, have 3/8"-24 threads on both ends and worked much better.
I also am replacing all of the 3/16" steel brake tubing on the Jeep as the original is 50 years old and most likely has had moisture in it at one time or another (cheap insurance).
The 72 Waggy backing plates bolted right up to my steering knuckles. No drilling or other modifications were required. It was a really simple conversion, not any more difficult than replacing the original 9" brakes.
Upcoming projects are:
- Converting the rear brakes to 11"
- Replacing the brake master cylinder with a dual chamber one.
- Installing a hydraulic clutch master cylinder and slave cylinder.
- Installing a set of swinging pedals.
The parts for items 2, 3, and 4 have come out of a 1980 CJ7 Renegade. Hopefully, I'll be able to adapt them.
tommy b