How to reposition UITableView?

Question

I have a UITableViewController and I want to add a navigation bar to it. So after the navigation bar (which works fine), part of the original tableView is being covered up by the nav bar.

I tried to reposition the table view using this:

self.tableView.frame = CGRectMake(0, 44 + 20 /* height of navbar + some margin */, 320, 416);

But the table won't position. Any idea?