audi q5 2009

The pistons are threaded and if you force them they'll become damamged. You need a special tool that's used to twist the pistons back in. (bought at any parts store). You insert an socket extension into one end, then line up the prongs into the holes in the piston and turn them.

Tell the parts store what vehicle you have and they'll tell you which tool fits.

If I'm correct your Audi Q5 has an electroni handbrake and there for you need to use some form of diagnosis pc to allow you to push the pistons back on your rear calipers.

Yes that is correct. I was unaware of that model year until I found it in Alldata.