Accually, I have tried both (placing them individually, or with array modifyer). In both cases, If their number was bigger than just few, the fbx refused to open. When I kept only about 5 piles, it did, butthe textures displayed incorrectly (it looked different in Blender and KSeditor). I believe there must have been something wrong with the mesh itself. I'll try making new tire model, maybe it"ll work this time.
This is how my corrent model looks like: