Where are Black Magic Brakes made?

We need to explore some of this. I don't know of a difference between the GM D-52 caliper for 2wd and 4wd. The clips below are of the buyer's guide on RA for that caliper. I'm not that versed in GM models but it looks like the caliper is used on both. If you look at the K-5 which is the Blazer, they show the RWD and 4WD as both using it.

I ran into this conundrum awhile back when helping someone with the front end on a late 70's Silverado: there was a changeover period when the front axle hubs, spindles, etc. were altered, and it seems that some of the brakes were affected as well...at least the data for them was affected, rather. When we started looking for aftermarket brake kits we found a lot of conflicting information; it indicated that there was a difference in the calipers (forgive me for not recalling the specifics) and that C-10 stuff wouldn't work on a K-10. Upon experimentation, however, we found that the D52 calipers did indeed work on both a 4WD and RWD, but they indexed in a slightly different way from one to the other. Nothing earth-shattering, but enough to where you would notice it if you were looking. I think it was something to do with the caliper mount being slightly thinner on one or the other, but don't quote me on that.
 
I ran into this conundrum awhile back when helping someone with the front end on a late 70's Silverado: there was a changeover period when the front axle hubs, spindles, etc. were altered, and it seems that some of the brakes were affected as well...at least the data for them was affected, rather. When we started looking for aftermarket brake kits we found a lot of conflicting information; it indicated that there was a difference in the calipers (forgive me for not recalling the specifics) and that C-10 stuff wouldn't work on a K-10. Upon experimentation, however, we found that the D52 calipers did indeed work on both a 4WD and RWD, but they indexed in a slightly different way from one to the other. Nothing earth-shattering, but enough to where you would notice it if you were looking. I think it was something to do with the caliper mount being slightly thinner on one or the other, but don't quote me on that.
Some of that is the aftermarket being confused. They used to list the WJ master as a step bore that had a larger front bore (back of master) and a smaller rear bore (front of master) because they didn't understand that the seal cap at the back was not part of the bore and was much larger than the actual bore which was just a straight bore.
 
Here is a lit of more common chevy calipers, all of these should have the 7" pin spacing. The low drag calipers require more pedal travel since the piston retracts back into the caliper more. Borrrowed from: https://www.gmt400.com/threads/jb5-jb6-jb7-jb8-size-thread.39647/

JB5(6400lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 11.86x1.29
Rear Drum- 10x2.25
Vacuum- Double Diaphram
1 3/16" wheel cylinder

JB6(7200lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 12.50x1.28
Rear Drum- 11.15x 2.75
Vacuum- Double Diaphram(same as JB7)
1" rear wheel cylinder. 11' drum has self activating shoes, therefore does not require as much pressure as the 10"

JB7(8400lbs)Single rear wheel:
1.25" Bore MC(used in JB5 and JB6 Hydro Units)
Conventional Calipers 3.15" Piston
Front Disc- 12.50x1.54
Rear Drum- 13.00x2.50
Vacuum- Double Diaphram(same as JB6)
1 1/16 rear wheel cylinder

JB8(10000lbs)
1.312" Bore MC
Conventional Calipers 3.4" piston
Front Disc- 12.50x1.54
Read Drum- 13.00x3.50
Hydraulic Hydro Boost
1 3/16 rear wheel cylinder

JB3 specs;
Front disc 11.57 X 1" with 2 1/2" piston caliper
Rear drums 254 mm X 57 mm ( leading/trailing)
Vacuum-- Single Diaphragm
The easy way to identify JB3 brakes is the front rotor is solid not vented. It was also identified as JN3 in the service manuals.
 
Some of that is the aftermarket being confused.

That's exactly what it is. We fought wrong part numbers right and left (literally) on that truck; time and again we would end up with a component that plainly didn't fit, despite what the numbers did or didn't tell us. Getting the correct brake parts finally required me ordering five or six different kits from different companies, and keeping the one that actually worked...and that came after my having called and asked some very specific and clear questions to people that should have known some very specific and clear answers, but didn't. In my opinion, there's no excuse for having someone available to answer technical questions, but who simply can't do that.
 
Here is a lit of more common chevy calipers, all of these should have the 7" pin spacing. The low drag calipers require more pedal travel since the piston retracts back into the caliper more. Borrrowed from: https://www.gmt400.com/threads/jb5-jb6-jb7-jb8-size-thread.39647/

JB5(6400lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 11.86x1.29
Rear Drum- 10x2.25
Vacuum- Double Diaphram
1 3/16" wheel cylinder

JB6(7200lbs):
1.574" Bore MC
Low Drag Calipers 2.935" Piston
Front Disc- 12.50x1.28
Rear Drum- 11.15x 2.75
Vacuum- Double Diaphram(same as JB7)
1" rear wheel cylinder. 11' drum has self activating shoes, therefore does not require as much pressure as the 10"

JB7(8400lbs)Single rear wheel:
1.25" Bore MC(used in JB5 and JB6 Hydro Units)
Conventional Calipers 3.15" Piston
Front Disc- 12.50x1.54
Rear Drum- 13.00x2.50
Vacuum- Double Diaphram(same as JB6)
1 1/16 rear wheel cylinder

JB8(10000lbs)
1.312" Bore MC
Conventional Calipers 3.4" piston
Front Disc- 12.50x1.54
Read Drum- 13.00x3.50
Hydraulic Hydro Boost
1 3/16 rear wheel cylinder

JB3 specs;
Front disc 11.57 X 1" with 2 1/2" piston caliper
Rear drums 254 mm X 57 mm ( leading/trailing)
Vacuum-- Single Diaphragm
The easy way to identify JB3 brakes is the front rotor is solid not vented. It was also identified as JN3 in the service manuals.
What are the JB numbers referring to?
 
Blaine, it is the option that GM used for the brake option on thier build sheets. There are JB and JD numbers for the K & C series trucks, burbans and blazers, the JD were used on Diesel engine vehicles. I had to look it up myself. I want to improve the braking on my waggy front YJ, so I found a set of pads that are larger than the standard pad that were used on cars with towing packages, they add about 2 square inches of pad area. That sent me looking at different calipers, which is how I found this info.
 
Blaine, it is the option that GM used for the brake option on thier build sheets. There are JB and JD numbers for the K & C series trucks, burbans and blazers, the JD were used on Diesel engine vehicles. I had to look it up myself. I want to improve the braking on my waggy front YJ, so I found a set of pads that are larger than the standard pad that were used on cars with towing packages, they add about 2 square inches of pad area. That sent me looking at different calipers, which is how I found this info.
An increase in pad surface area does not in and of itself correlate to increased stopping. The clearest example of that is the 833 pad used on the Sport Trac and the 477 pad on the TJ. 477 is considerably larger in surface area but driven by a single piston caliper doesn't make it nearly as effective as the dual piston pushing on the 833. The surface area in the single and the duals is nearly the same and it all boils down to better distribution of the force from the pistons and no pad flex. I've seen many overworked 477s with a low stop opposite of the piston. That makes it have to be flexed to bring that spot into contact with the rotor to get full braking after that happens.
 
Blaine, it is the option that GM used on thier build sheets. There are JB and JD numbers for the K series trucks, burbans and blazers, the JD were used on Diesel engine vehicles.
That is why I wanted to also increase the caliper bore size, its not perfect but it is one of the few options for my combination and not have to change knuckles on the waggy front end. My rear is a rodeo 44 with factory disc rotor and parking brake, I built a bracket to use the GM metric caliper, with the stock waggy caliper up front, my bias is a little heavy to the rear. If I go to a larger front caliper and a larger pad, I am hoping it will fix my bias problem. I also am using a mid-70s grand marquis master cylinder...Its a close combination but it needs some refinement. If I get it perfected, I hope to use it on my LJ with the HP44 and Rodeo rear. Tim
 
That is why I wanted to also increase the caliper bore size, its not perfect but it is one of the few options for my combination and not have to change knuckles on the waggy front end. My rear is a rodeo 44 with factory disc rotor and parking brake, I built a bracket to use the GM metric caliper, with the stock waggy caliper up front, my bias is a little heavy to the rear. If I go to a larger front caliper and a larger pad, I am hoping it will fix my bias problem. I also am using a mid-70s grand marquis master cylinder...Its a close combination but it needs some refinement. If I get it perfected, I hope to use it on my LJ with the HP44 and Rodeo rear. Tim
I would get the GM metric that has the smaller pistons and swap that on first.
 
Blaine, I have that on the rear...I think, this thing was built in 2008, so I dont remember all of the details. As I was building it, the original rodeo calipers were way too small, I used a set of speedway adapters to mount the GM metric calipers ot the rodeo. I also would like to have a little more braking for the larger tires, that I was looking at larger front calipers...
 
Blaine, I have that on the rear...I think, this thing was built in 2008, so I dont remember all of the details. As I was building it, the original rodeo calipers were way too small, I used a set of speedway adapters to mount the GM metric calipers ot the rodeo. I also would like to have a little more braking for the larger tires, that I was looking at larger front calipers...
I understood you have GM metric calipers. What is going to happen when you put larger brakes on the front is the weight transfer will go up and the rear bias will increase. If you have too much rear brake now, that will only get worse with larger front brakes. So, you will likely need to move to the smaller piston versions of the GM metric caliper.
 
Ok Blaine, I will be honest, I do not get the logic you are using...I am not saying its wrong, I just do not understand it.
 
Ok Blaine, I will be honest, I do not get the logic you are using...I am not saying its wrong, I just do not understand it.
More front brake means more weight transfer onto the front axle which removes the same amount of weight off of the rear axle under braking. That changes the bias to need less rear brake.
 
More front brake means more weight transfer onto the front axle which removes the same amount of weight off of the rear axle under braking. That changes the bias to need less rear brake.
Ok, I got that...what about using different pads in the rear?
 
Ok, I got that...what about using different pads in the rear?
That also works sometimes. The worst one I've dealt with was a TJ Buggy that had the bigger GM calipers front and rear. We wound up just barely getting the rear ones to almost not lock up by running an adjustable prop valve before the combo valve and cranked it all the way down to limit the pressure as much as possible out of the master.