So I finally had a look at the chop, I think your brushing is coming along nicely, but the image looks a bit flat and yellow. So this is what I did.
-(Playing with hue and saturation on the ground)
-Editing levels and contrast on the image)
-There are scratches on the front rim)
-There's a gap between rear arch and rear wheel
I cleaned up the image a little and then used a much whiter (less red) colour for brushing the highlights.
I think you are on the right track, just alot of little things to fix and you need to make the image cleaner. I'll give more C&C as you go along.