Require a star tool to remove disc rotor I need to change my disc brake rotors. I discovered that I require a star tool. Here is a picture of my rotor bolts. Can someone point out a tool that will fit this? Prefer a bike tool. 

To give some indication of its size. The first size of hex key that becomes too big to fit within the star is: 4mm. 3mm fits within the star.

I have one of those wonderful screw drivers that come with 40 or so heads to fit all those different screw types (cheap china Ebay job), but the star in this kit does not fit snugly and I don't wish to risk rounding.
You want the correctly sized Torx driver. When I had to swap to a new wheel set I used a T25 driver.

I just found a Park Tool TWS-2 that has 9 different sizes. You can probably find just a T25 driver at a hardware store.