One or both of the bolts holding your caliper in place loosened up and eventually (probably right before the time you heard the grinding) worked their way off. The caliper, now riding loose on your rotor, was driven into the inside of your wheel when you hit the brake, probably repeatedly. This would cause the caliper to wear through the thin aluminum rim very quickly OR flat out crack/break the rim almost immediately, (depending on how hard you hit the brakes, whether the wheel locked up or not, etc). Result would be a broken rim and a popped tire exactly as you describe, and the evidence for this will be 1) the free caliper and 2) the worn or cracked inner rim of the wheel probably with a groove worn into it where the rotor was biting into the wheel.

If you're lucky the tire just popped off the rim or lost air because the rim cracked/broke and it's reusable, and matching stock single rims are generally pretty cheap.

The lesson- make sure you properly torque down the caliper bolts. And stop immediately whenever you hear caliper noise to double check what's going on. Using thread locker would be another good idea!

Amac

 

 

Undertorquing the caliper anchor bolts is a common (and very dangerous) DIY error. These are the short, stout bolts, 2 on each side (#16 below). You didn't mention the year of your Ranger but the torque spec for many years is 85 lb-ft. This is much higher than many people would guess "by hand". Be sure to check your specific year to find the exact torque value and use a properly calibrated torque wrench.

Also, these bolts need thread locking compound. Ford recommends that new bolts with new compound be installed whenever disturbed. I doubt that everyone follows this recommendation but the thread locking compound is essential along with adequate torque.

The torque spec on the long slender caliper bolts (#17) is, of course, much lower than the anchor bolts. For many years, it is 24 lb-ft. Again, be sure to verify the exact value for your Ranger's year.