Tire model: https://grabcad.com/library/tire-rim-8

KeyShot Tutorial: How to create a dirty tire material. In this KeyShot tutorial I’ll walk you through the process of creating the look of a dirty tire. I’ll be creating a base rubber material and add a dirt material on top of that. I’ll show how to use the color composite node to blend a color gradient together with a bitmap texture to use as an opacity map for the dirt overlay.

0:30 : Create the base rubber material
2:05 : Create the dirt material
3:47 : Use a color gradient as opacity map
6:25 : Use the color composite node to blend the color gradient map with a bitmap texture