By Thunderstruck...
1. Front brakes
Upgrading the front disc brakes on your M body, or any of the F and J bodies as well, is fairly simple.
If you have the 10.5" front rotors you can upgrade to the HD 11.75" front rotors easily and fairly inexpensively. You will need the HD 11.75" rotors, the correct caliper adapters for the larger rotors and the type of calipers you are running. Your best and easiest bet is to look thru the boneyards for any mid 70's and up MoPar with the 11.75" rotors. Find the best examples you can. Grab the rotors and the caliper adapters. The caliper adapters are the mounts the calipers ride on, the adapters are bolted to the spindle. There are two different caliper styles on MoPars of this era. The slider type, which is what's on your M body, and the pin type. The slider type "slides" on a machined groove in the caliper adapter. On the pin type the caliper rides on a set of pins that screw into the caliper. Allegedly, the pin type is less prone to sticking, but my experience has been that if you properly rebuild your front brakes then the sliders work great as well. Some things to beware of, there are 4 possible caliper adapters, one pin type and one slider type for the 10.5" rotors, one pin type and one slider type for the HD 11.75" rotor. Be careful that you grab the right set up. Another potential "gotcha" is the fact that you will need to run 15" rims to clear the bigger rotors. You Copcar owners check first because I believe all actual Copcars, not the civilian type undercover copcars like mine, have the big brakes. To install the set up is very easy. Remove you caliper, rotor, and caliper adapter. Install bigger caliper adapter, rotor and reinstall your caliper, assuming your keeping the slider type setup and not going to the pin type setup. If you are going to use junkyard rotors resurface them. If you want to use junkyard calipers rebuild them. Rebuilding your existing calipers is a good idea in any event. Always replace the wheel bearings and seals if running used stuff. New semimetallic pads from a name brand supplier, bleed the system well and you ready to rock. I'd recommend a complete front brake system overhaul when your switching over. It's your life don't half @ss it. This is it. If you already have the big rotors then you have the best there is to offer short of a battleship anchor or your own mint.
2. Rear brakes
For those of you hoping to swap in a rear disc brake package I have good news and bad. First the good, there are at least two easy ways to swap in rear disc brakes. First, the mid 70's Imperial had a factory rear disc brake option, a few even had ABS! This system will bolt onto you existing axle with absolutely no modification necessary. Second, MP (MoPar Performance) has released a "race only" rear disc brake kit for most MoPar axles, including all the types factory installed in your M body. Ready for the bad news? Major financial backing will be required for the MP kits, which are not street legal, and the Imperial's rear disc rotor is no longer available new. Your only hope is to find a boneyard setup with excellent rotors or finding a set of new ones sitting on a shelf somewhere. Granted, it's been close to two years since I called everyone I could think of and then some. Someone might be reproducing them but I doubt it. If anyone knows of a supplier please let me know. I am looking into modifying a rear disc kit for the frod explorer for use on my M body's rear axle but I need more info before I try to con the OL into allowing me to spend the bucks.
Rear drum setup
The stock rear drums are adequate even with the HD front brakes. Remember the front brakes supply a majority of the stopping power. But if you got to have the biggest brakes around then scrounge the bone yards for an 11 x 3" drum setup. Donor cars will be mid 70's and later monster MoPars. New Yorkers, wagons, Imperials. Once you find the donor then grab the drum, the backing plate, and everything in between. You should replace all the guts but having the old stuff on hand will aid in getting the correct new stuff. Again, rebuilt, resurface or replace everything but the backing plate. Don't trust you life on boneyard brakes of unknown condition.
3. Safety considerations
Test your brakes in a safe area in a safe manner before you trust your life to them. If you forgot something the place to find out is not on the freeway at 70 mph. If your rear brakes lock up before the front then you can either go to a smaller rear wheel cylinder size or buy an adjustable proportioning valve, plumb it correctly into the rear brake line and adjust it so that the fronts lock up before the rears. Bleed your brakes thoroughly. Your pedal should have a firm feel to it with no mushiness. If you don't have the factory service manual get it, your money will be well spent. That about wraps it up. Any comments Email me.
© 1996, 2001 Email Thunderstruck