89 Corvette Brake Rotors 11.5" or 12"

[GKK]

I was wondering why the specs for my 89 Vette list the front and rear brake rotors as 11.5" and in all the Parts catalogs they list 12" rotors for an 89? Do they just round it off?

 

[Dougs91]

Wish I had some real "pro" answer for you but, I think they just round up like you said

 

[GKK]

Too bad the rotors aren't really 12" that would be nice. Thanks for the reply Dougs91.

 

[Ken]

1989 Brakes, Service:

Description: Hydraulic power brake front and rear disc base JL9 and heavy duty J55 systems

Brake type front: B.C.I.A. standard pin guided caliper

Brake type rear: B.C.I.A. standard pin guided caliper

Special valving type: Rear proportioner integral with master cylinder

Power brake: Standard

Booster type: Vacuum 9.4" single diaphragm 65 sq. in.

Vacuum source: Engine plenum

Anti-lock device F/R: Standard front and rear

Anti-lock manufacturer: Bosch

Anti-lock type: Electrohydraulic

Anti-lock number sensors: Four front wheel sensors

Anti-lock number hydraulic circuits: Three (two front, one rear) hydraulic

Anti-lock integral or add-on system: Add-on

Anti-lock yaw control: Yes

Anti-lock power source: Electronic motor pump

Effective area: 32.4 sq in (front), 18.4 sq in (rear)

Gross lining area: 33.0 sq in (front), 18.4 sq in (rear)

Swept area: 102.3 sq in (front base), 111.9 sq in (front HD), 91.3 sq in (rear)

Rotor outer working diameter: 11.9" (front base), 12.9" (front HD), 11.9" (rear)

Rotor inner working diameter: 8.75" (front base), 9.7" (front HD), 9.2" (rear)

Rotor thickness: 0.78" (front base), 1.1" (front HD), 0.78" (rear)

Rotor material and type: Gray iron vented (front), HCE iron vented (rear)

Wheel cylinder bore: 1.5" (front dual piston), 1.6" (rear)

Master cylinder bore: 0.87" (front), 0.87" (rear)

Master cylinder stroke: 0.79" (front), 0.47" (rear)

Pedal arc ratio: 3.5:1

Line pressure at 100 lbs pedal load: 1250 psi (front), 750 psi (rear)

Lining clearance: Self-adjusting, front and rear

Front brake lining bonding: Integral molded

Front brake lining manufacturer: Japan Brake Industries

Front brake lining code: JB CP26, FE code

Front brake lining material: Semi-metallic non-asbestos

Front brake lining size primary: 5.3" x 1.57" x 0.37"

Front brake lining size secondary: 5.3" x 1.57" x 0.37"

Front brake shoe thickness: 0.24"

Rear brake lining bonding: Integral mold

Rear brake lining manufacturer: Japan Brake Industries

Rear brake lining code: JB H3H B33, GF code

Rear brake lining material: Semi-metallic non-asbestos

Rear brake lining size primary: 4.25" x 1.38" x 0.33"

Rear brake lining size secondary: 3.7" x 1.38" x 0.33"

Rear brake shoe thickness: 0.16" (outboard), 0.22" (inboard)

 

[GKK]

Wow, that's a lot of Great information! That answered my question. Thanks, Ken