Rear Brake Rotor Size

[A26B]

SOmething is amiss, either the rear rotors on my ZR-1 or the GM Service Manual for 1994. Page 5B2-10 Rear Disc Brakes states Heavy Duty Rear Rotors, std on VIN J (ZR-1) are 13.0" dia x 1.110" thick. i.e. same as the front. My rear rotors are standard at 12.0" x 0.795". A quick call to O-Reilly's revealed they show the ZR-1 & standard Corvette have same rear rotors, only fronts are different.

Could someone tell me if the GM Service Manual is wrong, or do I have incorrect rear rotors? Thanks;help

 

[Rob]

Jerry,

Let me look into this and see what I can find.

 

[Rob]

I have listed that they are 12.0 front and 12.0 rear for both 1994 standard coupe and convertible. If you ordered a coupe equipped with the Z07 Performance Handling Package, the front brakes were increased to 13.0 in front.

The ZR-1 received 13.0 front and 12.0 rear. So a Z07 coupe would essentially have the same size brakes as a ZR-1. Does this help at all?

 

[A26B]

Rob: Well, that's what I thought until I read the 1994 GM Service Manual. Manual also says Z07 had 13" x 1.110" heavy duty rear rotors, same as ZR-1. Smells like a mistake in the manual. Thanks for your response.

 

[Hib Halverson]

The service manual is wrong. No 88-up car with J55 front brakes had 13-in rotors at the rear, too.

All 88-up cars have 12-in rears regardless of what's on the front.

 

[A26B]

Thanks Hib, always nice to have your valuable & accurate input. Will make a note in my 94 service manual accordingly.

 

[Hib Halverson]

Speaking of errors in the manuals from that period. As I recall there was a misprint in the 93 and 94 books as to brake caliper mounting bracket torque. The front torque spec. was misprinted as the rear spec.

 

[A26B]

Front & Rear Caliper Mounting Bracket Bolt Torque

94 manual has 166 +- 15 ft lbs & rear @ 70 ft-lbs

Did not readily find bolt size in manual, so I couldn't determine whether torque was reversed or not, however, there is a hell of a difference in torque, that's for sure.