Cycles removes assigned material from mesh faces altered by a displacement map, instead leaving them plain white Let me preface this with the statement that I'm a complete Blender beginner. Literally started modelling yesterday.

Here's the deal. I'm modelling a very simple tyre, and testing out different displacement map patterns, in order to be able to generate a nice complex tread in PS where I feel more confident, instead of having to model it directly in Blender. Here you can see said tyre in object mode with the map applied:



Whenever I render the image however, some weird artefacts show through on the tyre wall and more importantly, the tread grooves don't show the texture I have assigned to the mesh. It looks like this:



There is no doubt in my mind that this has some absurdly straightforward solution, but I simply have no idea what that might be. The only avenue of logic I can go down is that for some reason, at rendering time, the displacement map separates the mesh faces that it alters from the rest of the object, thus breaking the link between them and the assigned material. But what confuses me is why it doesn't do the same thing when I'm in edit/object mode.
OK, so this was not a Cycles problem.

Simply there is another tyre named "tyre2" in the scene which is hidden for the viewport but rendered :



To avoid it to be rendered, click also on the little camera icon on the right.