What Is the Difference Between JB6 & JB7 Master Cylinders?by Aleksey Alekseevich
The JB6 and JB7 are two of the most common brakes of the many available to GM vehicles. There are some differences in the two models that you should consider before purchasing a replacement set.
The brake shoe in the JB6 is 11 5/32 inches in diameter and 2 3/4 inches in width, while the brake shoe in the JB7 is 13 inches in diameter and 2 1/2 inches wide.
JB6 brakes are designed to handle up to 7,200 pounds of force, while JB7 brakes are designed to handle 8,400 pounds.
The JB7 brakes are a bit more expensive than the JB6 because of the more resilient materials that go into making the stronger brakes.
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