Not a 69, but it may apply as well.
Info gathered from 68 Chasis Service Manual; "When the total disc thickness is less than 0.965" for the 1" thick disc, or 1.215" for the 1¼" thick disc, it should be replaced".
Some applications I've seen, have the minimum thickness value engraved somewhere around in the disc. hope this helps.
A forum community dedicated to 1st generation Chevy Camaros owners and enthusiasts. Come join the discussion about performance, builds, restoration, modifications, classifieds, troubleshooting, reviews, and more!