Rear Disc Brake FAQ

[SlamChops]

Ok, I havent seen a rear disc (disk for added search) brake FAQ yet. I searched disc and disk and neither had a tell all FAQ for the conversion. Lots of good info if you want to sit there and scroll through each topic though.

All-Pro and Sky both sell brackets.

Rotors - commonly 89 Chevy 1500 Regular Cab 4x4 front rotors. Have to be the Regular cab rotors as the Ext. cab rotors are 5/16" thicker.

Calipers - 82 Chevy Monte Carlo front calipers or ?? Cadillac Eldorado rear calipers

The rotors have to be machined, torched, hacked open to fit the flange on the axleshaft. To fit an 86+ rear axle they must be machined to 4.19".

You must cut off or press off the backing plates from the drum brakes.

You can make, or buy metric to SAE brake lines to adapt from the toyota lines to the GM calipers.

If anyones got the links to the 2-3 disc conversion write-ups, please post them. I'll try and add some more later.

[Wally85toy]

Good call, would like to know all about it. does anyone have pics and dimensions of the brackets so we can make our own?

is there a rotor that you don't have to machine torch or hack to fit?

[Big_Ern]

Here's some more information I uncovered while researching for a disk brake swap (still haven't gotten around to it yet though...)

Calipers
napa pn 2422032 (caliper only $13.99)

vehicles:

chevy
78-83 malibu
78-88 monte carlo

Buick
78-85 Century
78-87 Regal

Oldsmobile
78-87 Cutlass (RWD)

Pontiac
78-87 Grad Prix
78-81 LeMans

(To find all these I knew that the early-mid 80's monte carlo calipers would work, so i took that number and crossreferenced what other vehicles use that PN on napa's website)


Brake line
raybestos BH38149
Once the rotors are clearanced and slid on and the brackets for the rotors are bolted on simply bolt on the calipers and brake lines and you are done! With the rubber brake hose you can simply run your existing hard lines to it.
(Got this info from a post on here, but I can't remeber by who)



Hope this helps

[Sir Flipsalot]

Here's Mine:

http://www.webercomputing.net/~aweber/truck/brakes.htm

[Wally85toy]

wow, good write up, only one question left. did you remove the rear lspv completely and just run the one for the rear off the master cylinder. and what about the other line to the prop valve, my 85 has 2 lines coming from the front.

I will re read and delete this post if it's there and i missed it!

i read it again, so you just plug it as close to the master cylinder as possible.

[DRM]

http://www.4x4spot.com/proportioning.htm

[Sir Flipsalot]

Originally Posted by Wally85toy

wow, good write up, only one question left. did you remove the rear lspv completely and just run the one for the rear off the master cylinder. and what about the other line to the prop valve, my 85 has 2 lines coming from the front.

I will re read and delete this post if it's there and i missed it!

i read it again, so you just plug it as close to the master cylinder as possible.

I removed the rear prop valve, plugged the second line at the tee by the front fender, and installed a Willwood Prop valve by the Master....

I think all of that is in the write-up... Been a while since I've read it....

[4RnrRick]

Heres some of my info to add to this FAQ.



This is how I'm setup:

Dual Diaphram brake booster from late model V6 non-abs 4runner
1" MC from late model V6 non-abs 4runner
Summit Adjustable Proportioning valve
SS brake lines front and rear
LC vented rotors and V6 calipiers
Sky's rear disc brake brackets
1" thk Chevy rotors
Monte Carlo Calipiers (mid size GM)
Not positive on brake pads but I think the fronts are Bendix SUV Semi Metalics which I have had great luck in the past on my old XJ and out back are napa brand cheapo's. (the idea is better pads up front to increase friction and cheap pads out back to reduce friction.)
Sky's transfer case parking brake
Total vehicle weight with a full tank of gas and me is 4500 lbs rolling on 36" IROK's (2400 front, 2100 rear)

The adjustable porptioning valve is adjusted all the way down so the minimum pressure is going to the rear.

And heres a post about some issues I've been having with my braking system:
http://www.pirate4x4.com/forum/showthread.php?t=248688

So I know my setup is not perfect but IMO its better then stock.




How to locate the bleeder screw properly......






Some really good info about brakes in general and a complete troublshooting guide. VERY GOOD INFO
Read this:http://www.mpbrakes.com/troubleshooting.htm





Those running rear disc conversion with cadilac eldorado calipers, read this:

Rear caliper problem -
If you are using Cadillac ElDorado rear calipers there are some important things you should know. One of the biggest advantages of a disc brake system is the fool proof self adjuster. Not so with this rear GM system. The rear calipers adjust off the parking brake. The parking brake is incorporated into the caliper. You must set the parking brake every time you park the car.The rear caliper pitons utilize a one way clutch inside the caliper piston. When the parking brake is applied the clutch senses when there is .030" or more clearence between the friction material and the rotor on the inboard side. When there is more than .030" the clutch turns inside the piston adjusting it out keeping the rear brakes adjusted. If you do not set your parking brake every time you will start to lose brake pedal (low and spongy) and the adjuster mechanism will not work any longer. Also: never use rebuilt calipers on the rear because the rebuilders use the old pistons and the pistons were the reason the caliper failed in the first place.

ref: http://www.mpbrakes.com/trouble17.htm



A plasma torch or a 4 1/2" cut off wheel on a grinder works best IMO for cutting the backing plates. Also the (4) stud are just pressed into the bearing closure plate so a quick tap with the hammer will remove those. Then you start cutting.

[4RnrRick]

Here a picture of how I did my setup in the rear.


I used a rubber flex brake line from a monte carlo and then cut the toyota brake fitting off and installed a GM one with a double flare tool. Then I slotted a washer and welded it to my ubolt plate and then mounted the brake line to that.

When doing the conversion you will also need to buy the 'floating pins' and the 'banjo bolt' which mounts the brake line to the calipier.

[4RnrRick]

About half the monte carlo calipiers I've seen have a smal nub on the inside portion of the calipier near the main piston. This nub interfers with ALL the disc brake conversion kits I've seen. And this nub is not needed and as far as I can tell serves no real purpose. All you typically have to do is grind off about 1/8 -3/16" of this nub and it will then clear the bracket.

On my personal 4Runner, One calipier had the nub and the other one didn't. inthe picture below you can see the nub just left of the upper nylock.

[4RnrRick]

Here is some info that Brandon put together:
http://www.rcrc4x4.com/TechReports/B...DiskBrakes.htm


Here is some info that RMW put together:
http://www.pirate4x4.com/forum/showt...hreadid=175742



10.0MM x 1.50 thread Banjo bolt part number for monte carlo caliipiers: NAPA part # 82703

[4RnrRick]

Some more very good info in this post:
http://www.pirate4x4.com/forum/showthread.php?t=105656


The flange boss on the toyota rear axles is 106 mm (4.173") so if you decided to bore the chevy rotors out yourself, just make them a bit bigger than that.

[SlamChops]

Awesome. This is coming together great.

Here's a little run down on how I got the backing plates off.

-Remove all the brake parts from the backing plate (throw in trash can or scrap bin)
-Make 2 cuts on the backing plate. On an imaginary plane across the backing plate.
-Beat 3 of the studs out (leaving one to hold the backing plate and bearing retainer from moving)
-Use air chisel to cut out the last 1/4" of the backing plate, and beat on it til it breaks into 2 pieces.
-Remove 4th stud and voila, done.

[ROKTOY]

'Bout 7 years old......but......

http://www.off-road.com/toyota/discs.html

http://www.mindspring.com/~jayk3/toyota/discs.htm

Jay

[OffroadRunner]

ricks bleeding tech is great. I never thought of bleeder screw not being drilled striaght in. Took about 4 nights and 4 qts of fluid before I posted with problems

Thanks Rick. for ya



to add some tech to my post. The offset between the rear flange and the caliper mounting postion is exactly 3/8 of an inch. using El dorado caliper and 95 1/2 chevy rotors

I made my own brackets with some 3/8 plate. Cut, welded and drilled. I am using El Dorado rear calipers. Choose them for the e brake. They didnt work so well. I could not get enough tension on the cable to hold the truck. The foot/floor mounted e brake levers must get alot more leverage then the toy hand brake. I would have to muscle the crpa outta the handle to get it to hold. After the 4link was done I never even bothered to hook it back up...

[4RnrRick]

OffroadRunner - No Problem....... I might have covered the problem your having with the El Dorado rear calipers ebrake at the bottom of Post #8 above..... Might be worth a shot for ya.

[Neil426]

I just did the rear disc swap myself with the chevy 1 1/4" master cylinder. The M/C was from a '72 3/4 ton P/U with front disc brakes. As posted above make sure you bench bleed it or you'll be there all day and use a lot of fluid. I re-flared the lines, metric to sae. As for the caliper brake lines I used '96 geo metro front lines. They are long enough to go over the springs and have two spring clip mounting points. I'm still using the lspv and the stock plumbing. The brakes work pretty good, rears will lock up easily, while the fronts are really hard. I think the M/C piston is about the same volume as front caliper piston volume so the mechanical advantage is moot. Hopefully when I switch to the vented rotors and Ifs calipers, the caliper volume will work in my favor other wise I'm in for a work out. Has any one else installed the 3/4 ton M/C with the Ifs and GM calipers ? Or is the 3/4 ton just too big?

[turbo4runner]

has any one used older 85ish supra calipers with the ebrake's. I saw that jay decided that they might not hold but has any one confirmed this. thanks

[Rockrat]

FYI when doing the caddy calipers on the rear if you have reversed rims with 12" centers and more then 2" b.s they rub the calipers

[waskillywabbit]

Originally Posted by SlamChops

Awesome. This is coming together great.

Here's a little run down on how I got the backing plates off.

-Remove all the brake parts from the backing plate (throw in trash can or scrap bin)
-Make 2 cuts on the backing plate. On an imaginary plane across the backing plate.
-Beat 3 of the studs out (leaving one to hold the backing plate and bearing retainer from moving)
-Use air chisel to cut out the last 1/4" of the backing plate, and beat on it til it breaks into 2 pieces.
-Remove 4th stud and voila, done.

So the backing plate just needs to come off and go bye bye? I want to make sure I'm not making this too simple. I have the brackets and the rotors, working on getting some calipers, but just wanted to make sure about the backing plate before I got started.

I'm also still not positive as to where to put the proportioning valve. In the engine bay after the MC in line w/ the rear line or back where the OEM LSPV is? Any recommendations on proportioning valves? I've found some at Summitracing and Downey but the price seems to vary greatly as does the idea of just exactly what I need.

This is what I have thus far: (85 4Runner w/ an 86 toy rear end)
All Pro brackets
All Pro rotors
FJ80 MC - installed
SS extended brake lines

[4RnrRick]

You are correct, just cut the backing plates off. you do not need them any more.

Heres the part number of the portioning valve I used: SUM-G3905

Hope this links works: http://store.summitracing.com/partde...rt=SUM%2DG3905




This is where I put mine.





And I removed my OEM load sensing valve which is above the rear axle. See this if your not sure how to do that:
http://www.pirate4x4.com/forum/showt...ighlight=valve
http://www.4x4spot.com/proportioning.htm

Basically you use remove it and then capp off the line that goes back up to the front brakes.

[4RnrRick]

Here is how ErikB did his....


http://home.4x4wire.com/erik/4runner...s2.htm#wilwood

[SlamChops]

i did go with an adjustable prop valve as i was locking up the rear a LOT earlier than the front. i got the summit adjustable and love it. i put it in the same place as 4RnrRick to keep it high and dry. Very happy with the disked rear.

[waskillywabbit]

Thanks guys for the info. Please forgive my ignorance. I've never messed with brakes before other than just changing pads and filling up the reservoir.

So far this is what I've got (correct me if I'm wrong on something please)
Rear disc conversion - (All Pro)
non ABS FJ80 MC - already installed
New manual PV in rear line by MC (Summit)
Plug front line return from LSPV on both ends
Bleed brakes
Adjust manual PV

Is there some initial setting for the manual PV or is it a trial and error kind of adjustment? Drive, slam on the brakes, adjust, repeat? Did you need any additional hard line/fittings - other than the plugs for the front line return off the LSPV?




Is this the general setup? I want to make sure I'm seeing this correctly.
1. MC to rear brakes via PV
2. From PV to rear brakes
3. MC to front splitter
4. To front driver's side
5. To front passenger's side

[4RnrRick]

My portioning valve is turn all the way one way and its still not enough for my application....... But yes, drive it and tweak as you go.