GM Service Manual Online
For 1990-2009 cars only

Component Specifications Brake Systems

System

Master Cylinder Diameter

Front Brakes (Disc)

Rear Brakes (Drum)

Rear Brakes (Disc)

Brake Assist

JB7

31.8 mm

1.25 in

318.8x39.3 mm

12.50×1.54 in

331.5x64 mm

13.00×2.5 in

--

Hydraulic Hydro-Boost

JB8

31.8 mm

1.25 in

318.8x39.3 mm

12.50×1.54 in

331.5x89.3 mm

13.00×3.50 in

--

Hydraulic Hydro-Boost

JF9

40.00 mm

1.57 in

357.0x36.7 mm

14.00×1.44 in

--

936.2x36.7 mm

13.60×1.44 in

Hydraulic Hydro-Boost

Component Specifications Rotor Thickness

Original

Maximum Refinish

Replacement (Discard)

32.51 mm (1.28 in)

31.25 mm (1.23 in)

30.86 mm (1.215 in)

39.11 mm (1.54 in)

37.59 mm (1.48 in)

37.21 mm (1.456 in)