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Discussion Starter #1 (Edited)
A little history... I drive a 2007 Colorado I5 4x4 with a 2.5" leveling kit and 31" tires on stock 15's.

In order to do this conversion if you are running the stock 15" wheels, you WILL NEED 1" wheel spacers as well as some trimming will need to be done on the outside brake pad and both caliper brackets.

To my knowledge, 16" or larger wheels (depends on offset as well) do not require spacers or trimming.

Did my best to take pictures throughout the process but didn't get everything. If anyone wants to see something I missed, I can try to get a photo of it at some point and add it to the thread.

Parts List (all from '06 Hummer H3 Base)
Rear Pads/Calipers/Brackets/Rotors Kit - Callahan Brake Parts CCK03327
Right Rear Backing Plate - ACDelco 15111378
Left Rear Backing Plate - ACDelco 15111377
Right Rear Brake Hose - ACDelco 1761468
Left Rear Brake Hose - ACDelco 1761469
2 M10x1.0 Inverted Male Brake Line Fittings
4 M12x1.50 30mm Bolts
4 M12 Washers
2 5/16x18 1" Bolts

Depending on where you order parts from will determine cost, my cost on all the brake parts was under $400. I did some research to find lower prices but the majority of it came from Amazon. If you need wheel spacers, it adds an additional $250 (roughly) to the bill.



Tools Used
3/8", 1/2" Impacts
3/8" Ratchet
1/2", 13mm, 18mm, 19mm Sockets
8mm, 10mm, 14mm Wrenches
Brake Line Flaring Kit
Cut Off Wheel
DREMEL w/ Carbide Bits
Acetylene Torch
MIG Welder
5/16x18 Tap (make sure to check drill bit size for this tap)
Air Drill
Hose Clamp Off Pliers
Paint Marker
Center Punch
Hammer

Start off with removing wheels and drums. I removed my rear diff cover (13mm socket) and popped the axles out (8mm wrench for diff pin bolt), I was overdue for a diff service so it worked out. Also used hose clamp pliers to pinch the brake hose to the rear end to minimize brake fluid loss. There are four bolts that hold the OEM backing plate on (18mm socket). Make sure to loosen the brake line at the wheel cylinder (10mm wrench) before removing these four bolts.



In order to install backing plates, a section has to be cut out to allow the backing plate to slide over the axle tube. The backing plate CAN NOT be mounted to the front of the axle flange because the rotor will hit the backing plate. Make sure to remove the section from the opposite side of the caliper mounting tabs. Backing plate mount holes also need to be notched or made oblong in order to bolt to the axle flange (H3 has a smaller mount pattern). I used a DREMEL to remove small amounts at a time, checking fitment often to only remove necessary amount of material (you can see the paint mark in the pic below to reference backing plate placement on the axle flange). Once this is done, mount backing plate to back of axle flange with the four bolts from the back side. Make sure caliper mount tabs are towards the front of the vehicle.



After the backing plates are installed on both sides, axles can be reinstalled as well as the diff cover and fluid can be added. Rotors are next and spacers if you have the stock 15" wheels on your truck. I went with BORA 1" Hub Centric Spacers from Custom Offsets because of the great reviews and Hub Centric design.



If you have 15" wheels, now is the time to trim the caliper brackets and outside brake pads for each side. I used a grinder on the outside edge of the brackets on both top and bottom. Pads done similarly, only a couple millimeters need to be removed from the top of the mounting tabs. Inside pads do not contact so trimming is not necessary.



Install brake pads into caliper brackets, then bolt to the backing plate with two of the M12x1.50 30mm on each side (19mm socket). Install caliper onto bracket (14mm wrench but may vary).



In order to install brake hoses and have a decent mount point, I used the thicker piece of steel from the section cut out of the backing plate(can separate the two pieces by chiseling off the spot weld between the two pieces), hammered it flat with a little persuasion from a torch, cut the rounded edge off, and welded it to the back side on the bump stop plate on the axle tube.







After attaching the piece of steel, I marked where I wanted the brake hose mount to attach and drilled/tapped a hole for a 5/16x18 1" bolt. The brake hose could also be attached by a self tapping screw if a tap set isn't available. Applied loctite to the bolt before installing (1/2" socket).





Now the hard brake line needs to be cut and re-flared. Make sure to install fitting onto line before flaring. Plastic coating on brake line needs to be removed before fitting can be slid on. Warming it with a heat gun makes removal with a razor blade a breeze. I flared my line by doing a double inverted flare which means bubble flare first then inverted flare. A single inverted flare would also work for this scenario. Make sure to NOT crack the line when flaring. If you don't have access to a brake line flaring tool, a local tool store may have one available for rent. YouTube also has some great videos on flaring brake lines. If your flare isn't straight, the fitting will leak. Practice on the excess line that was cut off if needed or cut the brake line a little long just in case.



The only thing left is to remove the clamp on the rubber brake hose to the rear end, bleed brakes, and install wheels. Gravity bleeding brakes went quickly, don't forget to check brake fluid before doing so.

First thing noticed on test drive was amazing pedal feel and noticeably less nose dive. Overall greatly satisfied with the outcome.

Congrats, rear disc brake conversion complete!
 

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Discussion Starter #2
Re: Rear Disc Brake Conversion Complete!

If you have ABS on your vehicle there isn't a proportioning valve so there is no need to install one. Rear fluid apply pressure is calculated by the ABS module and adjusted accordingly.
 

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This is awesome, i just swapped my front suspension and brakes to the h3 setup and was going to do the rear diff to get disc brakes in the back but it is good to know i dont have to do that. :th_woot::th_woot:
 

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This is awesome, i just swapped my front suspension and brakes to the h3 setup and was going to do the rear diff to get disc brakes in the back but it is good to know i dont have to do that. :th_woot::th_woot:
Interested in your H3 front suspension setup. Would like to hear more.
 

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Discussion Starter #9

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I think @rshadd has to approve the how to submission... I think
 
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