Here is a few things to help ya out

The Suspension Source: How To Properly Measure Vehicle Ride Height

 

I have a 2014 gmc with the factory 22s and factory 285/45/22 tires. I just did a 4/6 drop 2 days ago. I can tell you there is a lot of rub at the rear of fender well when tires are turned and at the top when you hit slightest bump in the road. So I'm like you I need to figure out something cause it rubs to much for my liking.

 

A little update: I put some 285/35/22 tires and have pretty much no rubbing. It has rubbed one time so far with the newer tires and that was at really big dip in the road.