Hey dude nice model but the shaders need a lot of work! your spec on the rubber and metal is WAY to high the rubber looks more like a hard clean plastic, rather than wet rubber, rubber even a new tyre has every lil or zero reflection on it, instead it gains most of its projected colour for the lights in the surrounding enviroment.
Im not sure if you modeled or used a displacement map on the tread, but tread have different levels of wear on them, also try adding a bump/light displacment map with soft noise to add some grain/texture.
Last but not... well just not. if your going for a wet tyre dull down the rubber and some water effects in photoshop, max's reactor or real wave and show the reflection in that, ie. wate between the tread gaps