I did a thing- 10 bolt rear disk conversion

[GAnthony]

I like the simplicity of rear disks and I read about the improved function of the NBS master cylinder but I didn’t want the cost of buying a kit to bolt or weld on. So I decided to do my own thing. The subject truck is my 93 Yukon GT. I bought cheap-ish front calipers and rotors from Rock Auto for a k1500 along with Delco brake hoses and a Delco master cylinder for a 2001 Yukon XL 1500. I just used some simple measurements and geometry to start with and kinda winged it making a template for the caliper brackets out of card stock and trimmed until it seemed like it fit the caliper well.

You must be registered for see images attach

I then traced that to some 3/8” plate I had and as steady as I could, plasma cut 2 pieces out by hand. After de-slagging and cleaning them up, I ended up with my rough cut.

You must be registered for see images attach

I was generous with the material left so that I could trim it for proper fitment. After fine tuning was done, I fit it to the caliper so I could mark fastener hole locations. I then drilled and tapped the holes for the caliper bolts.

You must be registered for see images attach

I anticipated welding them to the axle tubes but by dumb luck, the brackets lined up perfectly with the outer side of the mounting flange from the drum brake backing plates. I was able to clamp everything in place, mark, and drill holes in my brackets and use 2 of the backing plate holes for my new brackets. I did have to clearance my brackets around the axle tube to make room for a raised ridge/register on the original backing plate bracket which locates the backing plate properly. I sand blasted, hosed a coat of Steel-it on them, and the fit and finish turned out great. I welded some brake hose tabs on the axle tubes, cut and re-flared my steel lines and plumbed them up with banjo bolts that came with the new calipers. M10 if I remember right. I had to grind a small tab off the brake hoses for them to seat tightly on the calipers.

You must be registered for see images attach

(Pic before painted)

I had previously removed the ABS modulator and made lines to work without it but I’m sure leaving it in place would have worked fine as well. I changed out the master cylinder for the 2001 Yukon XL unit as well as changing out the combination/proportioning valve for a cheap brass PV4 from Amazon.

You must be registered for see images attach

The pedal feel great and the braking is seriously improved. I consider this a fantastic upgrade. Even though this truck is NOT a beauty queen and is more of a beater for me, I really love the way all of this worked out.

 

[Schurkey]

I hate to dump-on your dreams, but that's a train-wreck.

1. You've re-invented a flat-bracket disc conversion; and flat-bracket disc conversions are a mess. They load the caliper mounting pins/sleeves in a way they were never intended to be stressed. So that's gotta go. If you have welding experience, you could fabricate and weld-on caliper supports so that caliper thrust is taken by the welded-on supports instead of being taken by the mounting pins/sleeves.

2. The original drum backing plates attached to the axle in four places. Brake torque is split among four bolts. You've cut that down to two bolts, doubling the brake torque each fastener has to accept. That torque is in single-shear; which is even more difficult in terms of engineering.

3. You've eliminated the park brake. That's illegal in most if not all states. Probably against Federal law, too.

4A. If you have low-drag front calipers--and I'm pretty-sure you do--the new master cylinder is totally wrong for them. WHAT IS YOUR BRAKE CODE? Kinda guessing JN/JB5 or JN/JB6, either of those would have low-drag calipers, and REQUIRE a three-chamber (Quick Take-Up) master cylinder.

4B. Depending on what "K1500 front" calipers you bought, you may have put low-drag calipers on the rear.

5. Why would you eliminate the ABS? At least you had enough sense to retain a proportioning valve and safety switch.

 

[GrimsterGMC]

While I am all for coming up with new ideas, i have to agree with all of the points that Schurkey has made. I don't mean this as criticism, but for your own safety. Brakes are a complete system where each component has a role to play and it all has to work together. The worst part is if you look at your front calipers, as they fit into place in the front steering knuckle, you will see that they fits into the housing in a way that stops it from moving forward or backwards and that the bolts only hold them in that position. There is little to no loading on those bolts, but in your case the bolts will take the entire braking load and shear off in a short time.

 

[GoToGuy]

Where's the photos of being completed? What grade steel is that? What rotors? Are those the 8 mm backing plate bolts? Aftermarket kits use all four mounting bolts. Your edge to drilled hole distance would fail engineering and inspection criteria.
Of all the items on truck the most important to not cheap out , is being able to stop. Not having safe reliable brakes makes you a liability and a hazard to yourself and every other person on the road or near it.
There's a lot of really smart people, paid big bucks designing and engineering new replacement and hi performance aftermarket systems. Why would you try to reinvent the wheel?

 

[Scooterwrench]

I applaud your efforts to DIY but you really need to study the parts your working with to engineer your parts correctly. Toss those brackets and start again with brackets that correctly fit the axle tube and use all four bolts. Add caliper supports so that when someone pulls out in front of you and you have to jamb on the brakes the caliper pins don't sheer off. You can add a line lock to the rear system for parking brakes or buy calipers with parking brake capability and design around those(recommended).
When designing parts always keep in mind that Murphy is right behind you ready to kick your a$$ at any given moment!!!
Don't give up,just move on to the improved version.