The brakes on the original 1947 CJ-2A consisted of a single reservoir master cylinder, small 9" drum brakes at all four corners, and a transfer-case mounted drum style parking brake. For the lightweight stock CJ-2A, the brakes were adequate, especially off-road. The system was similar to the brake setup used on most vehicles of the era.
Fast forward to the 1970 CJ-5, and things hadn't really changed much. The drum size had been upgraded from 9" to 10" to increase the friction area, but the single reservoir master cylinder and original parking brake design persisted. Jeep wouldn't offer front disc brakes on the CJ until 1977.
Drum brakes, especially on the front axle (where approximately 70% of braking occurs), have some inherent drawbacks. First, they require periodic adjustment as the shoes wear to ensure optimal engagement to the drum face for effectiveness and so the shoes wear evenly. Second, because of the enclosed design of the drum, the brake dust tends to get trapped and must be hosed off with brake cleaner fairly regularly. Lastly, drum brakes perform poorly when they get wet, and CJs that see trail time are frequently exposed to water and mud - not a good combination. The other negative associated with early CJ brakes is the single reservoir master cylinder. Mounted under the floorboard, the brake fluid was susceptible to water contamination. And the single reservoir means that if a brake line gets damaged, you'll lose hydraulic pressure to the entire system, whereas a dual reservoir provides redundancy between the front and rear axles.
With these considerations in mind, I definitely planned some upgrades. Initially, I strongly considered upgrading to disc brakes front and rear, even sourcing many of the parts for the conversion. I also felt that the transfer-case mounted parking brake was unique and cool in an old-school sort of way, so I began sourcing parts to refurbish it. After researching my options more thoroughly, I decided to ditch the original parking brake. A lot of early Jeep owners complained about constant adjustments and maintenance, and poor performance from the parking brake even when in perfect adjustment. And when considering the overall weight of the Jeep with a fiberglass body, I determined that the original 10" rear drums should provide for ample rear stopping power, and decided to forego the extra expense of a rear disc conversion. It's worth noting that late 70's to early 00's CJs and Wranglers utilized a front disc/rear drum setup. I've owned a number of these Jeeps and never felt the OE brakes were inadequate when running tires 33" and smaller.
So the system I landed on would include front disc brakes, rear drum brakes, a firewall mounted dual reservoir master cylinder, a late model CJ proportioning valve, stainless steel brake lines, and a line lock to act as a parking brake.
Remember that I was swapping in a later model open-knuckle front axle from a '73 CJ. This simplified things, but the axle still came with drum brakes. Luckily, it's a simple matter to convert to discs on this axle, requiring only later steering knuckles, spindles, disc backing plates and caliper brackets, and the rotors, pads, and calipers.
While working on the front axle, I also purchased and installed a new set of Warn Premium Manual Locking Hubs. These hubs are a great upgrade in strength, and they provide smooth engagement to lock in the front axle shafts. They should last for years, but when the time comes they can also be rebuilt.
Once the axle shafts with new u-joints were inserted into the housing, I followed the service procedure for installation of the spindles, brake backing plates, caliper brackets, and Warn hubs. There's an important step to prep the rotors before installation. Most rotors come with a coating of lubrication left over from the manufacturing process and designed to protect the rotor surfaces. You'll want to use brake cleaner to remove this film completely. Then, use a fine grit sandpaper to scuff both surfaces of the rotor in a circular pattern - this helps the pad to bite into the rotor as it breaks in and prevents the rotor from glazing.
I installed the new rotors, pads, and calipers from NAPA. However, when test fitting the 15" wheels, I found that they contacted one small section of the calipers. So I used a grinder to remove just enough material (see pictures below) so that the wheels could spin freely without contact.
With the suspension installed, I took measurements at full droop for the brake hoses. It turns out that the stock brake hoses had plenty of length to accommodate the suspension travel, so I installed an OEM set in front and an OEM replacement in the rear. There are many sources for these OEM parts, but I sourced mine, and many other replacement parts, from 4-Wheel Drive Hardware in Columbiana, Ohio.
For the hard brake lines, I decided to splurge on a set of stainless steel replacements from Classic Tube. It would have been cheaper to purchase bulk brake line and fittings and bend and flare the lines myself. But this is very time consuming, and I know from experience that it can be tough to craft the tight bends that are necessary without crimping the tubing, and shaping the perfect angles can be a frustrating game of trial and error. Classic Tube has been in business for over 30 years, they produce a high-quality set with perfect length sections, flared and terminated ends, and exacting bends. Plus, the stainless steel material means never having to worry about rust-through. As a bonus, many of the sections that have the potential to rub against other components come sleeved with a durable material. I sleeved any additional potential rub spots in rubber tubing to prevent chafing of the lines while bouncing around off-road.
Since I was converting to front discs and a dual reservoir master cylinder, I installed a late model CJ proportioning valve along the inner framerail. This is the exact part that came with the front disc/rear drum equipped later CJs, so it was a no-brainer. The late model CJ master cylinder was also designed for this system, so a new one found its way onto the firewall. This is a major change, as the original lived under the floorboard and was actuated via a through-the-floor pedal assembly. In the Body topic, I detail the swap from the frame mounted original pedals to the late model firewall-mounted pedal assembly. To finish off the pedal to master cylinder linkage, I used an adjustable brake rod kit from Speedway Motors.
The rear drums (also from NAPA) were quick and easy, since I was dealing with OEM components. One item of note: since the 1970 CJ-5 used the transfer-case mounted parking brake, there is no provision for a rear axle drum parking cable. Also, a late CJ parking brake pedal assembly would not fit the CJ-2A body. After considering options, I chose an electrically activated line lock that I plumbed into the hard brake line just behind the proportioning valve. When activated, the line lock maintains the current hydraulic pressure to the rear brakes, effectively mimicking a cable actuated parking brake.