If you are breaking the bolts that hold the caliper in place then there is a problem with the fit of the caliper to the stationary part that the caliper mounts to. The bolts should not see any stress from braking action, the stress should be transmitted through the caliper assembly to the stationary mounting bracket. Look at where the front of the caliper contacts the bracket, it should nestle the caliper so it can't move either inward or outward when the brakes are aapplied, same with the rear end of the caliper. bg