Well the uv's are big mess.
I suggest you to redo your uv's
Check this out
in this image i can tell you which one is the wheel which one is the body ... in your it's difficult ... try google for some Tank Uv maps.
When i'm laying out Uv's
I always check how the texture will go onto the model by checker you should make it too. It's very helpful !
Gj on modeling part