This characteristic of SW seems to have changed at some point over the last couple of years, I don't remember it being this way, so I'm guessing there may be a setting to change it back...
Issue: I create, say, a rectangle, set the dimensions of the sides and then go to create a circle that I want to be tangent to the sides of a corner. When setting the tangent relations, SW changes the dimensions of the rectangle (that I drew first) to make the circle tangent to the edge, and not the circle dimension. Does it not make sense that a newly-created sketch object would want to have it's dimensions changed to fit whatever is there presently and not the other way around? This is a really basic thing, but it's fantastically annoying. Possibly just to me!
YES, I know I could smart dimension/set relations for the first object(s) to fully define before moving on, but that's another few clicks, of which we're all making a few thousand daily. In the name of speed, is there a setting that causes 'newer' sketch objects to change dimension in preference to 'older'?
How are you "setting the dimensions of the sides of the rectangle? If you're using the Smart Dimension tool then they shouldn't be changing. If you're setting them in the Rectangle's Property Manager then that's expected behavior, since those aren't driving dimensions.