AlkyIROC

My project on installing disk brakes onto my 9" but the same principal can be applied to just about any differential.

This is what I'm starting with. Ford drum brakes on a 9". It was the easiest way to install brakes at the time and served me well for many years. 11 x 2-1/4". It took a while to find a suitable drum. I think this was from a late 60's mid size car. I drilled out the stud holes for the 5/8" drive studs and used a die grinder to make the pilot hole a little bigger.



I was walking through the local auto wrecker last weekend and I spotted a 99 Jimmy with rear disk brakes. It uses aluminum PBR calipers. Looking at the design, I figured I could make these work for my 9" diff so I pulled the calipers and mounting brackets. The brake pads were in good condition so I took those also. The rotors were rusty but I didn't know if I would be able to use them or not. Taking the calipers home, I cleaned them up and painted them. Yes that is paint and not polished aluminum. One had seized slider pins but it didn't take much to free them up and get everything working the way it was suppose to.





Now the job of finding a suitable brake rotor. If your axles are in the Chev 5 x 4-3/4" pattern, just use the Jimmy rear rotors as they should slide right on with no modifications. My Weld ProStar rims are in the Ford 5 x 4-1/2 bolt pattern and my axles have 5/8" drive studs in the same pattern with no other holes in the axle flange. A good rotor choice would be one with a Ford pattern to make modifying easier. The Jimmy rear rotor is vented and is .790" thick and 11.61" diameter. Trying to find something similar in size, I considered Crown Victoria and Explorer rear rotors but they are a solid rotor that's .430" thick. Although they might work, looking at how the PBR caliper and pads fit, I figured once the pads wore down, they may fall out of the caliper support. Last choice was a 1990 Jeep Cherokee front rotor. None of these rotors would work because I needed a rotor that would fit over my axle flange. The only rotor that had a wide enough center because of an internal park brake system was the 99 Jimmy. I went to the local auto parts store and bought 2 Jimmy rotors. I drilled new holes for the Ford bolt pattern and made them large enough for the drive studs. I used a die grinder to shave off around .010" from the pilot hole so it would fit on the axle. Looking good so far. You can see the drum backing plate hanging down. I already use a steel braided brake line with AN fittings. Converting to the calipers will just need a banjo fitting.

AlkyIROC

Now to figure out the best way to mount the calipers. I did a lot of internet searches to see how others converted disk brakes onto a 9" and got a few ideas. Using poster board, I started making templates to see what might work.

First idea was a simple mount bracket that the caliper bracket attaches to. It would then be welded onto the axle tube with gussets for extra strength. Although this would work for a 4x4 or a street car, there's too many alignment issues to make it a good choice.



I found on the Currie site, a bracket design that attaches to the bearing flange then brings the mount out from under the rotor. I did a lot of measuring, cut out some templates from poster board then cut out some mock up pieces from 1/4" Lexan to see how well it would work. It actually worked very well however I didn't like the idea of only having 2 bolts holding the caliper side bracket to the bearing housing bracket.



I doubled up the mount bolts to 4 similar to the Currie design and made sure they would stay inside the inner park brake drum of the rotor then cut them out of 1/4" flat steel. I cut these with a jigsaw and took a lot of effort to make sure all the holes lined up in all the pieces.



When I did the mock up with the Lexan pieces, I determined I would need a spacer 1-1/4 to 1-3/8" long. I bought some heavy wall tubing. It's 3/4" OD and the hole in the center just allows a 7/16" bolt through it. This is the mounting hardware except for the parts to actually mount the caliper. 7/16" grade 8 bolts and stover nuts. The washers are used as additional shims to position the caliper bracket over the rotor. Grade 8 washers would be better but I don't have any.



Mounting the brackets to the diif looks like this. The axle flange bracket replaces the bearing retainer plate. With the backing plate removed, some washers were used as shims behind the bearing plate. Cutting out the center of the backing plate would make a perfect spacer but I didn't want to hack up the backing plate yet in case this conversion didn't work. The bolts go through from the inside out because it makes putting on the spacers and adjusting the shims easier later on. The holes to mount the caliper bracket are not drilled yet because I want to determine the exact position before drilling. I have a rough idea where they will go but those holes can't be guesswork.



Here's what it looks like on the backside.

AlkyIROC

Now we're starting to get somewhere. Installing the rotor just to see how much clearance is available. The bearing retainer plate clears the inside of the rotor perfectly.



I slipped the caliper mount and pads over the rotor to position them. I wanted to make sure the mount wasn't sitting too low where it would ride on the top of the rotor or too high so that the pads would ride above the rotor. Using a simple clamp, it's held in place.



Looking down on the rotor, you can see the clearance. Mount to top of rotor is good and the spacers/shims between the two brackets center the mount over the rotor.



And how it's going to look from the backside. I didn't have room to drill the holes with everything installed so I marked the holes, removed everything and drilled the holes in a drill press.

AlkyIROC

The original caliper mount used 10mm bolts. I drilled out the holes in the mount to use 7/16" grade 8 bolts. There was no easy way to bolt the caliper mount to the bracket. Bolts couldn't be installed from the inside out and there isn't enough room to put the nuts on the inside. The alternative was to weld nuts to the inside. An alternative option would be to drill and tap the holes in the bracket plate to just thread in the 7/16" bolt. 1/4" thick steel may or may not provide enough thread though. I decided on welding nuts to the backside. When I had the brackets off to weld on the nuts, I painted them. I drilled holes through the head of the bolts then lockwired them to prevent them from coming out.



With the caliper mounted, it looks good.



Looks good at the rear also



I installed the wheel but should have turned it for a better view.



This is a 15" diameter rim with 5.5" of backspace. There's lots of clearance between the caliper and the rim. All I need now is to pick up some banjo to -3AN fittings to hook up the brake lines.



Cost to do the conversion.

2 Calipers, mounts and pads from auto wreckers. $37
2 New rotors $90
Fasteners, spacers etc $25
Steel to make the brackets was free from work but I'll put a value of $10. The steel was 5" wide x 1/4" thick and to make the 4 brackets (2 for each side) I used less than 2 feet.

Total parts cost $162

I spent about 10 hours just designing and making the brackets. It took a couple of hours to install and I still need to put on the passenger side, get some banjo fitting and bleed the brakes.

My car now has 1999 GMC Jimmy rear disk brakes on a 9" diff.

For even better braking, there's no reason this design can't be extended to the front side of the axle tube and a second caliper added.

AlkyIROC

Picked up the banjo fittings today. Two for $23. That increases the conversion price to $185. I can't include the cost of the brake lines because I had already converted to steel braided lines from hard lines last year. How you hook up your lines is up to you as an added expense.

I was asked how much of a weight saving the swap did.

I put the complete backing plate, shoes, wheel cylinder etc into the drum and put them on a scale. 32-3/4 pounds. Times two equals 65-1/2 pounds for the drum brakes that were on my car. The smaller GM drum brakes will weigh less. I forgot the bearing retainer plate but that's very minimal.

I then put the remaining rotor, caliper, caliper mount, mounting brackets and hardware onto the scale. 24-1/2 pounds. Times two equals 49 pounds.

For less than $200 I improved my rear brakes and reduced my unsprung weight 16-1/2 pounds.

AlkyIROC

I finished up the passenger side today and while looking at my accomplishment, I realized that this type of conversion is a specialized disk brake system. There is no parking brake system. If you need or want a park brake, you'll have to either adapt something else or try to use the Jimmy park brake system and caliper mount that's designed to fit into these rotors.

For a custom application that doesn't require a park brake, there's no reason this type of conversion can't be done to any diff. It basically just bolts to the housing end so you need to make a template to use whatever type of housing end is on your diff.

morepowerjoe

Nice job!

skirkland1980

iTrader: (2)

looks good. mine has a 28 spline ford 9 inch. i just used the 1995 crown victoria rear brakes. fit perfectly with minimal grinding to the caliper bracket.

U.S.Marine09

do you have the stock brake booster? proportioning valve and master cylinder?

RED_DRAGON_85

do i read this correctly to mean that you would put two calipers on one rotor?

AlkyIROC

No brake booster. No combination valve but I do have a manual proportioning valve mounted beside the seat to adjust how much line pressure goes to the rear brakes. Master cylinder is an aluminum GM version from an S10 that had manual brakes.

Dual calipers are possible but there's more to it than just that. Each caliper set should have it's own master cylinder and lines. It's a complete dual system. Vehicles like dragsters which have no front brakes will run a dual rear brake system. For them, the second set is controlled by a hand lever attached to another master cylinder. When you're trying to slow down from very fast speeds, the extra calipers will really help. Even when using a parachute to slow down, you still need a good braking system.

Andrew91GT

Awesome idea, thanks for sharing!

kmcn47

this is AWESOME, but i'll admit, i am a complete novice with axles and brakes, more of a body guy well body kid (18 as of june) can this be done to my stock axle? i know i'll have to weld the mounting brackets on but after that will there be any heavy fabrication, if i get the setup form say, i s10extreme?

T/Aperformance

To me that realy looks scetchy. I my self wouldn't trust a set up like that.
Why didn't you just buy new axles with the correct bolt pattern. Or better yet. just buy a complete rear end with everything you needed. You know they sell them like that.

cw3adkins

Cost...and quite frankly, if you look at some of the "GM Rear Conversion Kits", Alky has a very close design in comparison (maybe even better than a couple that I've seen out there). He basically saved at least $200 on his conversion; the cheap conversion kits from Jegs or Summit starts off around $400, Baer and Wilwood just skyrocket from there into the $700-1100 range.

I think Alky did a BA job and this is defiantly on my crap to do list now.

AlkyIROC

Plus those GM rear conversion kits still use steel calipers while I went with aluminum PBR calipers.

Buy a complete rear end? Gee, somebody has some deep pockets. Even to buy new axles it could cost me at least another $600. I'm not in the US so cross border freight is terrible. And why would I need new axles anyway? For the bolt pattern? I have a bolt pattern template to redrill the rotors to the Ford bolt pattern so there's no misalignment issues there. If I got new axles in the Chev bolt pattern, that would mean buying new rims also because my rims don't have a dual bolt pattern. Even if my rims were in the Chev pattern, the rotors would still need to be drilled for the 5/8" wheel studs.

This design is basically identical to what I've seen available from Currie but it's made specifically for my car. There's nothing wrong with it strength wise and provides more than enough stopping power for my race car. It's a fraction of the cost of a higher end system like Wilwood, Baer, etc and if anyone has a small amount of fabrication skills, with some planning and preparation, they can reproduce the same thing.

It's to show you want can be done on a DIY budget instead of plopping down many hundreds or thousands of dollars on a store bought system than may or may not be exactly what you want or it may not even fit exactly the way you want. Most of those kits are designed for a small handful of applications. 12 bolt, 9" for Torino ends etc. Even trying to adapt Explorer or Crown Vic brakes means modification work because I use the Ford old big bearing ends. Doing a custom installion like this allows you to modify and adapt this system onto any differential. The only adaptation part is the bolt pattern to attach the mounting bracket to the housing ends.

AlkyIROC

The price of used parts has gone up. I went to the junkyard to look for more stuff and decided to grab another pair of calipers with the mounts. I didn't see any good used pads but that isn't a big deal.

When I first started this project, calipers, mounts and pads were $37. Today, a pair of calipers which included the mounts but no pads, came to $41.50 after all the taxes, fees and surcharges were added on. Still a hell of a lot cheaper than an aftermarket aluminum caliper.

This winter I'll redesign the mounting bracket to make a dual caliper system. I've asked someone else who did a dual system. Simply tee the brake line off the one caliper to the other. Keep the bleed screws to the top so the second set of calipers will be flipped left to right since they'll be mounted in front of the wheel.

Sandgroper

Nice work! I want to put 4 wheels discs on my 1987 Camaro. It's got a Borg Warner rear end, and I'm in Australia so the parts should be easily accessible.

Those PBR brakes are Aussie too aren't they? Do you know what GM Holden models they are from?

AlkyIROC

No idea but try looking on early 90's models for something similar.

white_ghost

Nice job on fabrication. Looks clean. I however went the other direction and found replacement axle with everything I wanted on it. Needle in a haystack trying to locate a 91-92 Camaro 10bolt with Posi and disk. but after a week of trying to mount in a 95 Camaro rear diff and showing a real crappy looking stance. But my new baby Rocks for less than $300 plus new rotors.

Annihilate

iTrader: (1)

IF you could update this with working pictures, that would be great. Thanks!

curtalert89

So the same concept should work for my stock thirdgen rear end with fourth gen calipers and rotors with the mounts?

85IrocZ-28

I just did this recently:

https://www.thirdgen.org/forums/brak...pbr-brake.html

LS1 and LT1 axles are different lengths (according to stuff I have read on this site...). Depending on your application, you may have slightly different spacing needs. But the link above will show you what worked for me.

My link above describes the process of swapping brakes from a 93-97 F-body. The 98-02 are commonly referred to as LS1 calipers, and the process would be different. I believe there are more challenges with parking brake cables when swapping the LS1 calipers over. The reason I did PBR's is that the rotor is only 1/2 inch smaller (but already an inch larger than the Delco Moraine 3rd gen) and the caliper bore is exactly the same as the LS1. Other than a bit larger rotor acting as a heat sink, I didn't see a dramatic of enough different to warrant the LS1 on the rear (and I picked up the PBR's for pretty cheap).