Your wheel will be 'dished' incorrectly if your chainstay is out of alignment. but it will still be straight. You probably need wheel dishing tool. Are you riding a carbon bike or alloy? I really need a hanger straightening tool, hit a rock a month ago, almost killed the derailleur (L limit screw was ripped off), and hanger was bent. But I still couldn't justify getting a RM200-300 tool for basically 1 time use. I just use a spanner to bend it back.