Detailed Disc Brake Swap Info



I have been running my rear disc conversion since 1995. With the help of others I've been able to compile results of about 8 different rear disc brake coversions. I know many others have completed this swap, but I have only gotten feedback from a handful of people. Click here to see the original rear disc conversion I did on my truck. Below is a detailed report of the parts and methods others have used.




MODEL OF TOY
Swaps were done on '83 to '88 trucks and 4Runners. Conversions for all models should be similar.


YEAR OF REAR AXLE
Same comment as above.


CALIPERS USED
Most used 79-85 Cadillac El Dorado rear calipers w/e-brake. Mid 80's Olds Toronado, and I believe Cadillac Seville, are other sources for these calipers. One person used 78-83 vintage Monte Carlo front calipers, but these offer no e-brake capability.


CALIPER MODIFICATIONS
Most people did no caliper modifications. Two reported they ground a bit off the calipers to clear specific tire weigths. One also reported he did slight grinding of the pads to remove an edge that was cutting into the rotor.


ROTORS USED
Everyone used '86-'89 Chevy light pickup 4x4 vented rotors, measuring 1 inch thick.


ROTOR MODIFICATION
All commented that the center hole was enlarged to clear the axle ring.


E-BRAKE INSTALLATION
Some reported using line locks and not using the cable operated e-brake system at all. Most fabricated some way to mate the Toyota e-brake portion to the caliper portions. Custom cables or adaptions using cable clamps were two possibilities.

I personally used two stock Cadillac e-brake cables in the rear. The passenger side one comes forward and is clipped in place through the original hole in the frame crossmember. The driver side cable is much longer and is routed over the rear driveshaft and gas tank and is clipped into a small mount I made that bolts to the frame crossmember. These two cables mate to an equalizer bar actuated by the original forward cable. Crimp style cable clamps are used to secure the cables.

My e-brake works so-so. It can hold the vehicle ok, but not stop it. There are two main factors that prevent mine from working as well as it should. The Cadillac calipers require a fair amount of force, but more importantly, need more pulling distance than the stock Toyota brake pull has. One solution suggested to me would be to add a simple pulley setup to double the pull distance of the cables. I have not yet tried doing this.


TYPE MOUNTS USED
Most used homebrew mounts made from 3/8" flat steel, based on my drawings. One person used 1/4" flat steel (bent for the offset) and several people purchased and used TSM mounts. All reported bolting the mounts to the axle flange.

One person reported rotating his caliper mounts to the top of the axle to get the maximum ground clearance for the calipers. The only downside is that the calipers must be removed from the mounts for bleeding.


MASTER CYLINDER USED
Stock master cylinders were found to be too small, not moving enough fluid for the large domestic calipers. The favored choice was a 1" bore unit, typically from a later model truck or 4Runner. One person used a FJ80 master cylinder (but with the V6 IFS calipers for a better flow match). Dave Schneider also reported that the 93-95 non ABS 1 ton T100's have a 1 1/16" bore master on them.....yet another possibility.

When picking a truck or 4Runner master cylinder, Karl Bellve says the cast iron masters ran from '89 through 10/90. These are the best bet to provide good clearance if you have a cruise control option. Also, the brake resevoir and cap comes with a new master cylinder from Toyota. Aftermarket rebuilds do not come with the resevoir and cap, so you will have to find a salvage one or buy new pieces.


BRAKE BOOSTER USED
Most all used the stock booster. One person reported using the 2 stage Land Cruiser booster for better pedal advantage. I have also heard that the FJ80 booster will fit and provide better boost than the truck unit. However, I have not confirmed or fully compared dimensions.


PROPORTIONING VALVE USED
Methods ranged from using the stock LSPV and adjusting it as needed to replacing the LSPV with an adjustable valve such as those made by Wilwood. In any case, this is one parameter which requires some experimentation and adjustment based on your specific vehicle and brake setup.

In my case, I kept the original brake plumbing configuration, along with the LSPV. I eliminated the active LSPV adjustment and made it fixed by making a small plate that permanently holds the LSPV rod in the bias position I want.


RESIDUAL VALVE USED
A residual valve is a form of check valve that is inserted in the brake line and maintains some pressure in the downstream portion of the line at all times. These typically come in 2 lb. (disc) and 10 lb. (drum) ratings. Normal use is to maintain some line pressure for cases where the master cylinder is physically mounted below the height of the calipers. These are typically placed as close to the master cyliner as possible.

It varied as to whether or not people were using residual valves. At the suggestion of Mathieu Noualy, I tried a 10 lb. residual valve in my rear setup and this improved pedal travel significantly. I did not mount mine near the master cylinder. Instead, for ease of installation, I simple installed mine in the metal line between the LSPV and the rear brake hose. This has worked fine for me with no signs of pads dragging on the rotors.

If the residual valve were mounted closer to the master cylinder, I am not sure as to what affect the different pressure ratings would have on the pedal performance and possible pad dragging.


HOW IS BRAKING PERFORMANCE?
Everyone really liked the braking performance. Mud, silt, and gravel accumualtion in the drums was a thing of the past. Brakes dried and stopped quickly after water crossings. Response was smoother than drums and stronger, a plus when running bigger tires. Carrying a spare rear axle is now easier since the drum and large backing plate is no longer needed on the axle shaft.


HOW IS PEDAL TRAVEL?
Pedal travel was poor with the stock master cylinder, requiring two pumps to get enough fluid in the rear calipers to get them to function fully. Once filled with fluid, they worked great. Moving to the 1" bore master made the pedal travel acceptable to some, but the residual valve was needed to satisfy others.


INSTALLATION PROBLEMS
No one reported any real problems installing the brake system. Some had problems with pedal travel until they made the further mods mentioned above. A number of people did comment on how hard it seemed to get the calipers fully bled. I had this same problem during my initial installation.


CONCLUSIONS
The overall consensus indicates this swap is a good one. Braking performance is increased to help offset the increased load due to larger tires. Smoothness is up and the brakes stay clear of dirt and debris.

Since you're dealing with your braking systems, please do not attempt this mod if you do not feel comfortable doing it. Safety is of utmost concern here!

Realize that some tweaking may be necessary to setup the system properly for your truck.

I'd like to say thanks to the guys (you know who you are) who took the time to provide me with the feedback so that I could compile the info you see here. I really appreciate it!


Thanks for reading!


Copyright (c) 2000 by Jay Kopycinski, All Rights Reserved.