Starting with the structural aspect to your wheels, you're generally doing quite well, but I have two main concerns:

• Your wheels tend to be very cylindrical, and don't generally feature much widening through the midsection (or at least can definitely be exaggerated in that regard). While this widening isn't required, at least some subtle arc to the profile of the wheel is present to an extent in most consumer vehicles. The ones that are more straight across tend to be intended for more industrial purposes, and are made of much thicker rubber. The arcing profile that we get from having the middle section get a little larger gives a better sense that the tire is inflated, and that it would land with a bounce rather than a heavy thud. When it comes to this widening, I'm less worried about the degree shift (some of the more reasonably priced ellipse guide solutions students pick up can be more limited in this regard), due to the thickness of a wheel being fairly minimal, and thus incurring less foreshortening - but rather the physical size increase of those center ellipses are more important, since it's a matter of the actual structure we're looking at, rather than the application of foreshortening.

• You've done a good job when it comes to establishing the side planes of your forms (like the spokes that comprise your wheels' rims, where you didn't just establish their outward face but rather established their thickness as well to help provide a more solid structure), don't fill them in with hatching or solid black. This, while not exactly form shading, still uses the same principles where we're making a surface lighter or darker based on its orientation, and as noted here in Lesson 2, form shading is not something we employ in our drawings for this course.

Continuing onto the textural aspect of the challenge, this is actually something of a trap I've laid for students to help highlight areas of the course they may have left behind - namely the principles of implicit markmaking from Lesson 2's texture section. Given that our tire treads are made up of individual forms that rest along the surface of a larger form, they lean heavily into what we'd consider texture for the purposes of this course, and Lesson 2 is pretty specific on the importance of employing implicit markmaking when conveying texture, rather than explicit markmaking.

The difference being that implicit markmaking is strictly a matter of thinking about and understanding a given form as it sits upon that surface, and drawing the shadow it would cast - the resulting shape establishing the relationship between the form casting the shadow, and the surface receiving it. When students forget about this concept, they're more prone to either attempting to draw each textural form in its entirety through constructional and explicit means (which can result in very dense linework creating unintentional focal points that will draw the viewer's eye whether you want it to or not), or doing what you appear to have done here - which is more drawing the texture you see more purely from observation, painting the individual marks on one by one as you see them. The result here is that the marks are more vague, not directly tied to the forms casting them (because the step necessary to think about what we're observing tells us about the forms that are present is being skipped).

This can also occur when students, in dealing with textures that are composed of holes, or grooves, or even cracks, focus on these things that they can name (holes/grooves/cracks/etc) as being the textural forms in question. Of course, they're not - they're an absence of form defining an empty space, and it is the walls that surround them that are actually the textural forms we deal with, as further explained in this diagram.

Now, as I stated, this is a trap that I've laid out. It's very common for students to be so far removed from Lesson 2, and to not go back and continue to address the exercises laid out there as part of their warmups, that they forget about those principles. As such, I won't be holding you back on this account - rather, we'll use it as a bit of a firm reminder that there are principles from previous lessons that you may have let slip, and that you should be sure to go back and review those concepts. One section I would strongly recommend focusing on in particular are these reminders.