I'd have to agree with Mike about the corosion. You should try to make the corrosion texture look like it has been affected by the shape and contour of the drums rather than just having it wrap unaltered around edges on the surface.
I also feel that all the colour in the texture is a bit too bright and spectacular. I'd remove a bit of brightness as well as reducing the contrast.
Take a glance at my <a href="https://forums.simplymaya.com/showthread.php?s=&threadid=9428"><b>Porsche 959</b></a> WIP