From: Benson on
here is my wheel pic
http://i47.tinypic.com/k06jib.jpg

how can I find the centre and radius for the wheel(size of wheel)

only the steel(what) part of wheel,not include tyre. I've been try to used the
Detect circles with various radii in grayscale image via Hough Transform

but not really work, can someone please help me?
This is really important for me. Thank you.