brake system differences

Discussion in 'The Garage' started by stizkidz, Jan 25, 2005.

  1. stizkidz

    stizkidz 1/2 ton status

    Nov 11, 2004
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    near Atlantic City, NJ
    Can anyone tell me the difference between these 2 brake systems: JB7 and JB6

    I am looking up parts under the truck that I got my axles from, which is an 85 K20. However under anything relating to brakes there are different parts depending on JB6 or JB7 brake systems... I need to know which one to use if I am putting everything in my K5 using the stock K5 brake system.
  2. AkMudr

    AkMudr 1/2 ton status

    Dec 30, 2004
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    Ive got an 85K20 and I know from experience the differences from JB6 and JB7 are in A) Caliper piston size, B) Rear shoe size and brake master cylinder...

    I do know that I personally am runnin the JB7 setup cuz I just changed my calipers.


    JB6 - 2 15/16 piston
    JB7 - 3 5/32 Piston

    The calipers do look different as well when comparing a JB7 and J6 caliper.

    Also, measure the rear drum size....there are 2 sizes for shoes.

    JB6 11 5/32 X 2 3/4
    JB7 13 x 2.5

    The master cylinders are the easiuest way to tell..if yer reservoir is plastic with a, JB6...all cast metal, big in side like a "normal" MC should look like...JB7.

    I'm not an expert but those are the things Ive come across becuase I found myself asking the same thing when I had to get new rear brake parts for the first time. Hopefully someone else can chime in with what they know.

    If you need some caliper pics for comparison let me know I can take a pic of mine.

    I'd be willin to bet they are the same as the brakes on my truck. (JB7)
    Last edited: Jan 25, 2005

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