Ok guys, this is a semi-detailed tutorial on how to make your chopcar look like its moving with some extra tips and tricks.
First choose an image to chop. I chose this Mini because it's a side-on shot and they're realatively easier to work with than 3/4 angle shots. Although you can make other angle shots work, its just a little harder.
Original
Ok next, we're going to need to select the rims. I sometimes select the tire also if it has some writing or contrast to it. This one's tires are realatively dark so I didn't bother. Here's your selection.
I went ahead and duplicated the background nad copied the rim and made a copy of the rim layer. If you did as I did, you should have 4 layers: Background, Background Copy, Layer 1, Layer 1 copy. Select the bottom rim layer and go to Filter>>Blur>>Radial Blur. Use the settings shown. Make sure you keep the selection active. If you didn't keep it, Ctrl+Click on the rim layer to get it back.
You can check to make sure that it looks OK by turning the top rim layer off. Now, select the top rim layer and, again, go to Filter>>Blur>>Radial Blur. Use the settings shown.
Now, turn the opacity of the top rim layer to around 40-60% depending on the image. This will help show the spokes and add a bit of realism to the image. Instead of a frying pan, you get a spinning wheel.
Repeat those steps for the rear wheel. Now, Merge all the layers together (I would merge all 4 rim layers with the background copy because I do not like editing the background that much. I would end up with 2 layers). and make a copy of the newly-merged layer. Go to Filter>>Blur>>Motion Blur. Use the settings show here if you are editing the Mini shown. If not, you may have to adjust the angle and distance feilds to make it look good. Use your head with this.
Ok, now use a soft eraser at a low opacity to erase where you would like to have the car in focus. I chose the front. Here's a picture of the progress.
Alright, you're done! Keep in mind that cars speeding away without drivers are a bit on the un-realistic side, so if you are trying to acheive realism, make sure to add one. Either that or tint the windows so that they're real dark (not reccomended). Also, if you're planning to tint the windows, make sure you do that BEFORE you apply the motion blur, otherwise it will be very messed up. However, applying a blur of this scale on a chop is not reccomended as it hides all those awesome details you might have been working on. This is the same principal for blinding headlights.
And here's the final product.
Hope this helped.