I've got a 93 convertable. On the passenger rear caliper the 11/16 mounting bolt is bottoming out on my rotor. I only have 41,000 miles. The question is, (Is this normal for worn pads or is the cailper bad?). I bought new pads but I am unfamiliar with this type of caliper. Any leads on how to change pads would be appreciated.

 

I am assuming you are talking about the rear caliper bracket bolt that holds the caliper bracket to the whell hub housing...

I just put new pads and rotors on my 93 at all 4 corners. My first bit of advice would be to obtain the factory service manual for the 93 corvette (published by Helms). The whole process is detailed in there.

Now back to those bolts....

They should be discarded whenever the caliper bracket is removed from the hub housing. Maybe someone did a brake job on your car and used a different bolt? Anyway, the bolts come pre-treated with a threadlock and need to be tightened to 70 ft./lbs. They should not touch the rotor.

BTW, the current GM p/n for the caliper bracket bolt is either 14084051 or 14084053 (I think it's the latter). If it was my car, I check them out.

-Ed

 

The OEM caliper bracket bolt should not come close to touching the surface of the rotor. The bolt is a grade 10.9 and it's possible that somebody replaced the bolt. BTW, all of the bolts are supposed to be metric sizes so it is a 18mm head, but an 11/16" will work in a pinch.

While the OEM bolts do have a threadlock material on them, they really can be cleaned up and reused. I clean the threads on a wire wheel on a bench grinder and then apply a coat of blue threadlocker. If you use the red threadlocker, it will need heat to release that material.

To remove the caliper to install new pads, use a large C clamp to push the piston back into the bore (you should suck about 2/3 of the brake fluid from the M/C reservoir before doing this) Place the clamp against the bolt that holds the hose fitting in place and the screw end of the clamp against the backing plate of the outside pad. Tighten the clamp until the housing moves enough to see some spece between the outer pad and rotor face.

Remove the top caliper guide pin bolt. This is the small (15mm) bolt that goes thru the upper ear of the caliper. This bolt also has some threadlocker on it so clean it up (if you don't buy new bolts). The bottom bolt stays in place if you are only replacing the pads. Pull the top of the caliper backwards as it will rotate on the lower guide pin.

Then simply remove the old pads and replace with the new ones. Note that the inboard pad has a wear sensor. Make sure this pad is on the inside and the sensor in in the trailing position when the rotor rotates in a forward direction. Also there is a spring clip at the top of each pad backing plate. The ears of these must sit in the recess on the inside of the caliper where the gap is. You can see how they sit before you pull the old ones out.

Then rotate the caliper with the new pads back into position and replace the upper guide pin bolt (add some blue threadlocker to the end of the bolt threads and tighten to 26 ft-lbs. Refill the M/C reservoir with fresh DOT3 fluid.

If the rotor is scored enough because of the contacting by the longer bracket bolt, the caliper and bracket must be removed to pull the rotor. The parking brake aduster will have to be removed from the caliper (it doesn't have to come off with just a pad replacement. Remove the cable, remove both guide pin bolts, then the bracket mounting bolts (these need a 21mm socket). The rotor then simply pulls off. Then reinstall in the reverse order. The bracket bolts are 70-ft-lbs.

The service manual does not recommend turning the rotors if the grooves are deep. There is very little material on the rotor to remove before it reaches the minimum thickness as stamped on the rotor. They really are not expensive so it would be worth a new rotor.

 

Thanks Eschoendorff and C4cruiser. Yes it is the caliper bracket bolt rubbing on the inside of the rotor. I have had my C4 since 94 when it had 9000 miles so this would be the 1st brake job. I have decided to let my GM tech. take a look at it. I do appreciate your help. And Thanks again.