This tutorial with guide you through how to enlarge the wheels on your car:
Original
Larger Wheels
1. Open your image in Photoshop. I am using this Aston Martin V8 Vantage that I have modified in a previous tutorial.
2. Using the elliptical marquee tool, create a selection around the size of the wheel.
3. It is unlikely that you will be able to make a selection the same size as the wheel with no modifications to the selection. Go to Select » Transform Selection.
Only select the front face of the wheel, we can paint the inner part in later on.
4. Press Ctrl + T then expand the wheel to fit inside the wheel arch.
In the bubble you can see that the inside of the wheel needs to be made bigger. but we couldn't do this with the selection as it would of gone over the wheel arch.
5. So just use the dropper tool and paint in the extra area of the tyre. Then repeat the process for the rear wheel.
6. End Result:
More Tutorials: 
