I've got a Ford 9" with late style tapered roller open big bearings. I am converting to disc brakes. The end play/preload is apparently determined by the bearing retainers. The oem bearing retainers were removed and replaced with the caliper mounting brackets, which will now control that end play.. I've gotten several references to shim to"proper end play", but I don't know exactly how much or how little is acceptable. So, that's my question...what's an acceptable range? I have a feeling I'm opening a can of worms here, but hopefully not.