These are the large 10.9 grade bolts that hold the caliper bracket. I think the torque spec varies over the C4 generation so look it up (it is a BIG torque spec). I humbly suggest that at every oil change you put a 20mm socket on them and make sure they are tight. The general tells us to replace these bolts whenever they are removed. This is because they come with a thread locker on them to resist vibration. The dealers don't stock this part often (GM P/N 14084051). Most people simply reuse the bolts when replacing rotors. If you reuse the bolts then clean the threads with a brass or stainless brush and apply thread locker to them for reassembly. I use medium strength Loctite. But you should do your own research for the thread locker to use since I'm no expert.

The reason I'm posting is because I found a loose bolt on my wife's car this week because she told me there was a strange, intermittent noise. A forum search revealed that when these bolts fall out, the caliper can rotate on the remaining bolt and lock into the wheel. You can imagine the results of a wheel lock at speed without my painting that picture any further.

The jackass who didn't look up the torque spec and who didn't put thread locker on the bolt at the last rotor change was none other than me. But you will not make the same mistake I made.

 

I reused mine, and used blue Loctite. Good idea to re-check them, though!

 

Oh no, I had one off and used never seize on reassembly. Come to think of it, I've been using never seize for 20 years on caliper bolts and never had one come loose before.... what makes the vette different?

Edit,
If I remember correctly they were 18mm on my 85

 

I think you're good for the caliper to bracket bolt. But the bracket to knuckle/hub bolt is HUGE.

This pic is from a C6 but shows the bolts I mean clearly enough. (Socket is on the top one)



(lifted the pic from this thread)

 

And here it is on a C4...

(just to the left of the brake line)

 

I think the torque spec on the later C4s is 165 ftlbs. +/- 15. I also use blue Loc-tite.