A DTI is a dial test indicator

cheap ones measure in .1mm increments
good ones measure in .01mm increments
Expensive ones measure .001mm

to do the bearings with the wheel on you have to use a steel rim or make up a rod with some magnets on it that will stick to the rotor and measure the rock off of that at about 8 inches from the center of the axle


IF there is any noise in your bearings after you get them set up with the requisit tension/freeplay you need to at least pull them down completely and clean them for inspection... I skip this step and just replace them if theres any doubt at just over $100 for enough bearings to replace all the wheel bearings its cheap insurance and if the old ones come up apples you have a spare set.