I've pretty much finished the normal map for my tyre now. I unwrapped and baked it differently this time. I unwrapped it so I had the whole of the tread, including the bits on the curve, unwrapped together so there is no seams. only the inside circle where the text is is separate. This leads to less distortion and seams :D
Secondly I baked the tread detail from a flat geometry, my high poly tyre without the bend modifier attached. I also made the flat plane I was baking it to more high poly so that there was less distortion in the round edges of the tyre. doing this meant that the bake did not take the curvature of the tyre into account, and so it was cleaner and did not make a seam where one end would have joined the other.
Lastly I made it tileable in photoshop to get a higher resolution part. This means that half of the tyre tread is tiled.
In the picture I've shown (from right to left) the high poly, the low poly (200tris) and a more detailed low poly (350tris).
I am going to aim to use the higher detailed low version because cylinders are one object that really distort when viewed from certain angles, especially with a normal map applied. I feel that extra 150tris really make a difference.
Overall I happy with it, I will get on the diffuse and specular today, which should really make the details pop.