Disk Brake Conversion for a 1954 CJ3B

[bmorgil]

Your thinking is correct AJ. The proportioning valve is the key to balancing front to rear brake force. Locking up the rears before the fronts will cause spinning, especially in a short wheel base. Front discs and rear drums were quite common in the 70's and 80's. The front brakes do much more of the work than most realize. The harder a vehicle is able to stop with the front tire brake combination, the "G's" it can pull from the front, the more the weight will shift to the front. Eventually if you can get the traction and the brake clamp, lifting most of the weight off of the rear tires altogether. I have seen a few tire brake combinations pull some serious G forces on a skid pad. In some cases you could adjust the rears almost completely out.

To compensate for the pressure differential requirements of Drum / Disc, a combination valve is used to compensate internally. https://www.ebay.com/i/264968429497?...kaAhBKEALw_wcB It does a few things to make the drums work smoothly with the Discs. I would recommend using the dual master cylinder recommended by the people you are buying the kit from. They had better know if their kit needs a proportioning / combination valve or not. In any event you described how to adjust a proportioning valve perfectly. You go out and lock them up. Fronts must lock first. For street cars we always tried to lock the fronts and barley drag the rears. When you are track adjusting a lot of factors come into play. That is the benefit of adjustable over non adjustable proportioning valves. Its not a big deal. I can tell you know what your doing. Don't let it scare you off if you want some nice brakes. Order up your favorite kit, put in a Dual Master cylinder and a combination valve and you will love it I am sure. You don't need anything fancy or adjustable unless you want that. A simple off the shelf 1970's era gm combination valve will do the trick.