Very nice work! Starting with your constructions, there are a number of points here that make it clear that you've been quite mindful of how each wheel and its various elements exist in 3D space. I'm especially pleased to see the bulging of your wheels through the midsection, which helps emphasize their "inflated" nature, rather than making them feel overly stiff by sticking to a relatively straight cylinder. You've also been quite careful in constructing all of the complex elements of the rims/spokes, despite the size restrictions imposed by your ellipse guide. Through most of these you did not merely capture the face of those rims, but their side planes too, making them feel like more than just a paper cutout.

Now, one of the biggest things about this challenge is that it's a trap - we're so far removed from Lesson 2 and its texture section that students have a tendency to forget about the distinction between implicit and explicit markmaking. Not you though! You clearly still remembered the concepts, and used them quite extensively here. There are clear signs that you're thinking about each individual textural form along the surface of each tire, and considering the specific nature of the shadow it would cast upon its surroundings. This stands out most of all on the 'chunkier' tire treads.

While there's still some room for improvement - specifically when it comes to controlling the gentle falloff from larger shadow shapes to smaller ones that ultimately allow us to control the textural density in our drawings (number 2 is particularly weak at this, as it ends up maintaining the same density throughout its surface, resulting in a fairly visually distracting tire tread that would not really work in the drawing of a larger vehicle, as it would become an unintentional focal point drawing the viewer's attention), you are progressing nicely, and honestly I'm just really thrilled to see that you're using cast shadow shapes, and not merely filling in the side planes of your textural forms as some students do.

So! All in all, fantastic work. I'll go ahead and mark this challenge as complete.