This is my first ever tutorial I hope someone makes use of it. :)
1] Get your self a good picture and load it in to Photoshop
2] Duplicate the picture Layer > Duplicate Layer.... > Ok
3] Repeat step 2 so it looks like this
http://img61.echo.cx/img61/8321/3layerpic6lo.jpg
4] On Layer 1 copy 2 cut out the front wheel so you are left with this :-
http://img96.echo.cx/img96/4519/frontwheel7fi.jpg
and then do the same to the back wheel but one the next layer down (Layer 1 copy). You should be left with the front wheel on one layer, the back wheel on the next layer and the whole picture on the last layer.
5] Click on the layer which has the whole car on it and press Crtl + T and squeeze the car together so it looks something like this :-
http://img204.echo.cx/img204/9932/squeeze1cl.jpg
6] Now bring your fully sized wheel layers onto the squashed car and line them up so it looks like this :-
http://img204.echo.cx/img204/7341/wheelson7yr.jpg
as you can see it looks very rough so all thats left to do is to use the eraser(& the clone tool if needed) and clean up the wheel arches so it blends into the car and you should be left with something like this.
http://img151.echo.cx/img151/1663/astonmartin9ct.jpg
Hope it makes sense. :)