Details of the results!
Man, those are looking GREAT !
On the first one if you make one of the scaling numbers a negative number your sidewall will be the correct way.
Your grooves in the rotor are too deep back off on the height of your bump.
On the first three images you need to make that ground shadow darker that will really set your vehicle in the scene. So what I do is make a seperate pass just for the ground shadow. Link the whole vehicle together so you can make it a flat black with one click. :) then pick a dome that gives you the ground shadow your looking for,render it and add it in Photoshop or what ever software your using for post.
This will only work if you render a tiff with alpha. Really that's all you should render images as. Not jpeg
Thanks for sharing.
Tim