I think my 88 C1500 has JB 0.1Burb has JB7 and my sierra has JB5
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I think my 88 C1500 has JB 0.1Burb has JB7 and my sierra has JB5
So is the sales code simply referring to the different brake size setups? Or are there actual hydraulic differences in how they setup the brakes by RPO? Now I'm gonna go sort thru mine and find out which brakes I have - If I know I have a 14-bsf with 6-lugs, are all the brakes for that particular axle gonna be the same RPO?I'm a firm believer in replacing brake parts by rpo code. some rpo's are better than others and if you get into swapping brake parts because just they fit, could actually impair the brakes due to mismatched master cylinders with mismatched brake cylinders or calipers. so if someone wants to upgrade the brakes you need all of the parts for that particular rpo code.
sometimes people report good brakes after swapping in a 2002 tahoe mc.... but it just so happens to be of the right size for their rpo code.... meaning they kind of just got lucky. I think JB3 might be the ****** brakes found on a lot of pickups and they could benefit from an upgrade. otherwise the others just need to be fixed.
IMO of course but.... but it's simple hydraulics.
Al
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Richard
I'm JB6 so I guess my squishy pedal and "just okay" braking performance are probably due to old hydraulics and O'reillys brake parts lmfao.here is the thread that contains all the info.
JB5 JB6 JB7 JB8 Size Thread
Hello, After hours of looking around i can't find a thread that list all the sizes of the various brake components of JB style brakes. Please let me know if what i have so far is correct. I'm sure i have things wrong as all info is coming from other threads. JB5(6400lbs): 1.574" Bore MC Low...www.gmt400.com
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.
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
notice theres conventional calipers and low drag calipers... that's another reason that these rpo codes are important... see that thread to learn the differences....
Good info right there.......I'm a firm believer in replacing brake parts by rpo code. some rpo's are better than others and if you get into swapping brake parts because just they fit, could actually impair the brakes due to mismatched master cylinders with mismatched brake cylinders or calipers. so if someone wants to upgrade the brakes you need all of the parts for that particular rpo code.
sometimes people report good brakes after swapping in a 2002 tahoe mc.... but it just so happens to be of the right size for their rpo code.... meaning they kind of just got lucky. I think JB3 might be the ****** brakes found on a lot of pickups and they could benefit from an upgrade. otherwise the others just need to be fixed.
IMO of course but.... but it's simple hydraulics.
Al
Good stuff! I have vented front rotors, so it looks like I have JB5 brakes, and all I need for JB6 is to replace the rear drum assemblies!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.
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"
Another way to think about the hydraulic relationship between master cylinder and piston is to compare it to gearing. We downshift (small drives large (gear wheels)) when we want more force at the driven wheels. The same is true for the diameters of the pistons in a hydraulic system.Pinger,
Thank you for the info. I didn't take the larger bore into account. Reality; I failed to read thru and fully understand the rear disc conversion instructions before I purchased and installed. It goes without saying I probably should have. if just to know the science/math behind it. Shame on Me.
At this point I've decided to purchase the front caliper upgrade and rear disc conversion to go with my already installed LS Mfg MC. "If your gonna do it, do it right! " Thanks for the assist.
As far as the GMT800 to GMT400, I've done a bit of light reading since your post and it seems the larger bore falls in line with the LF Mfg MC science. And.....im guessing the larger pistons in the front calipers address the small reservoir in the LS Mfg MC otherwise, they wouldn't recommend buying all three as a kit.
Thanks again
Is the 7200 supposed to be the GVW of the truck? Mine is a half ton but it is the F44 half ton, I've never seen 7200 anywhere on it (even tho apparently my JB6 brakes are 7200), I think mine says 6600 or 6400.here is the thread that contains all the info.
JB5 JB6 JB7 JB8 Size Thread
Hello, After hours of looking around i can't find a thread that list all the sizes of the various brake components of JB style brakes. Please let me know if what i have so far is correct. I'm sure i have things wrong as all info is coming from other threads. JB5(6400lbs): 1.574" Bore MC Low...www.gmt400.com
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.
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
notice theres conventional calipers and low drag calipers... that's another reason that these rpo codes are important... see that thread to learn the differences....