This is interesting, I don't think I've seen it before. First off, make sure you've set the tangent space (in the per-mesh properties) to sync up with 3d app you baked it (max, maya, xn, etc).
Secondly, try turning off contact refinement on the shadow casting light(s) and see if that helps.
Have you tried the two things that I suggested? If you have and didn't see any change in the result, please upload the TB2 scene, model and normal map and I will take a look.
Hey, sorry for the delayed response, I've been battling a post-GDC flu. I took a look at your scene and it looks like the horizon occlusion function is causing the issues here, set that to 0 and the artifact should go away.
You always may get better results if you bevel those outside edges, at the moment the lowpoly doesn't quite match the shape of the highpoly there it seems.
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Secondly, try turning off contact refinement on the shadow casting light(s) and see if that helps.
https://www.dropbox.com/s/8whu82bcr7efgqu/wheel.zip?dl=0
You always may get better results if you bevel those outside edges, at the moment the lowpoly doesn't quite match the shape of the highpoly there it seems.