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**aotte1** · 01-30-2016, 08:06 PM

Some background information on the JB5 brake option or heavy duty brakes. I selected 1979 for both front and rear brakes to make them match, only need to remember one year. The front Dana 44 is a '79, so matched the rears to it. As mentioned before doing brakes system as complete JB5 option. So directly from the GM '79 brake chart for a K10 JB5 are the rear brake specifications:

Drum - 359492; size is 283.2mm x 69.8mm
Wheel cylinder - 18004890 (diameter is 23.8mm)
Master Cylinder w/Boost - 18004252 (Delco Moraine, 28.57 mm dia); optional Bendix M/C = "KP"; booster = tandem vacuum 18003681
Combination Valve - 18002887: metering = 517 kPa, split point 1379 kPa, slope = .41
Backing plate:
Flange plate & brake asm LH = 14009889
Flange plate & brake asm RH = 14009890

The 69.8 mm is 2.75 inches. And 283.2 is about 11.15 inches

The brake chart information is provided by Keith Seymore, a member here.

01-30-2016, 08:06 PM	#211
aotte1 Senior Member Join Date: Oct 2013 Location: lousiville Ky Posts: 2,637	Re: 64' K10 Project Long Bed Some background information on the JB5 brake option or heavy duty brakes. I selected 1979 for both front and rear brakes to make them match, only need to remember one year. The front Dana 44 is a '79, so matched the rears to it. As mentioned before doing brakes system as complete JB5 option. So directly from the GM '79 brake chart for a K10 JB5 are the rear brake specifications: Drum - 359492; size is 283.2mm x 69.8mm Wheel cylinder - 18004890 (diameter is 23.8mm) Master Cylinder w/Boost - 18004252 (Delco Moraine, 28.57 mm dia); optional Bendix M/C = "KP"; booster = tandem vacuum 18003681 Combination Valve - 18002887: metering = 517 kPa, split point 1379 kPa, slope = .41 Backing plate: Flange plate & brake asm LH = 14009889 Flange plate & brake asm RH = 14009890 The 69.8 mm is 2.75 inches. And 283.2 is about 11.15 inches The brake chart information is provided by Keith Seymore, a member here.