I spotted the photo editing lowering of a car thing in this thread so I thought I'd give it a go myself. Results are pretty neat for my first time. I need my car back now so I can take some better pictures and try it on some new angles and scenes.

Then I just need some coilover to gain the effect for real

You've done ok but you need to darken the top of the tyre to make it look more realistic and the front shadow needs to move closer, same for all shadows really. Hope this helps.