I am able to true my rear disc brake so there is clearance from the pads while working in my apartment. However, when I get to where I ride I find that it's rubbing and squealing. It's pretty hot right now. What's going on here? Do I have air in my line that is expanding in the heat? Is my wheel flexing under my weight? Is it possible that the rotor is changing shape slightly in the heat. This is driving me nuts so any help would be appreciated.