I would start with a sharp B&W drawing such as the Goodyear image I posted. (In that example I did not re-draw it - it's just a PNG image taken from the web.)

Pull the B&W image into https://cpetry.github.io/NormalMap-Online/ and adjust the Blur/Sharp slider. That will define the softness of your Normal Map which you then apply in your render program.

You can experiment with height map grayscale images and blurring in your source image, but I think the sliders in the app are all you will need.

I also came up with a technique to make a repeating Normal Map pattern from a MoI 3D model and it worked very well. But I'll be doing a tutorial on that in early summer as part of a larger car model tutorial.

Ed Ferguson