Everyone needs to practice their ellipses more. We allow (and more importantly encourage) students to use ellipse guides because at this point, the expectation is that students will not have had enough mileage throughout the course to be able to nail their ellipses in a way that does not detract from the core focus of the exercise. While we do allow students to freehand them, it's less of a "if you'd prefer" and more of a "if you can't reasonably find an ellipse guide". So, I'm glad that you changed your mind early on.

As far as the structural aspect of this challenge goes, you're doing great. You're mindful of arcing its profile through the midsection so as to create the impression that the tire is inflated rather than solid all the way through, so it feels as though it'll bounce rather than landing with a heavy thunk.

I do think you could stand to be a bit more mindful of your linework as you add freehanded structural elements though - I'm thinking that perhaps due to the smaller scale of the drawings, you may end up forgetting to use the ghosting method and to apply the principles of markmaking from Lesson 1, resulting in more repeated strokes and forms that don't feel quite as solid as they could due to rougher lines.

Carrying onto the textural aspect of this challenge, I'll admit that this is something of a trap. It's very common for students this far into the course to have largely forgotten about the specific principles shared in regards to texture back in Lesson 2, and instead of reviewing it they kind of end up guessing at how they should be tackling these problems. This challenge allows us to highlight that and stress the importance of reviewing old material, rather than simply trying to rely on memory.

One of the core principles of texture is that we tackle it not by explicitly drawing the textural forms themselves, but rather by implying their presence by drawing the shadows they cast. Looking at your wheels here, many of them look quite nice, even with the very heavy concentration of visual information, but if we were to use these as part of a larger vehicle, each wheel would become a focal point, drawing the eye due to the concentration of ink, whether you want it to or not.

Conversely, working implicitly as we see here in this example of african bush viper scales allows us to control how much ink we use to capture the information, without changing the nature of the texture being depicted. This gives us greater compositional control, and the ability to intentionally guide the viewer's eye around the image.

Now, while you're certainly falling into the trap of working with explicit markmaking instead of implicit, there are some places where you're attempting to work more with filled areas of solid black, but use them to define the side planes of your forms, rather than a separate cast shadow. This is still form shading, which as explained here should not play a role in our drawings throughout this course.

It's easy to end up conflating cast shadows with form shading, but it all comes down to thinking about how the marks you're making relate to what you're trying to depict. A cast shadow is generally a separate shape which defines the relationship between the form casting it and the surface receiving it. These notes go over how we should be thinking about our textural forms to decide how our shadow shapes ought to be designed.

The other thing I wanted to address are cases where our textures are made up of shallow or narrow grooves. These cases can be especially tricky because we're prone to treating the thing we can name - the grooves themselves - as though they're the textural forms in question. Of course they're not - they're empty space, with the textural forms being the walls that rise up around them, casting shadows onto each other and onto the floor of the groove itself. While the distinction can be very small, and we can even get away with just drawing the grooves themselves in many cases, it still professes an incorrect understanding of the nature of the forms at play.

Here's a diagram that goes over this concept.

Now, as the "trap" was intentional, I don't hold it against students and assign revisions based on that. I'll be marking this challenge as complete. Just be sure to take some time to review the material from Lesson 2 before continuing forward.