Before I get started, I did want to mention that freehanding ellipses is not something I would recommend. It's more that there are students who simply have a very tough time getting their hands on an ellipse guide (even the more affordable master ellipse template we recommend) - and so if a student is unable to get their hands on one, they are permitted to freehand their ellipses instead. It's simply going to make the exercise more difficult, and as a result, make it somewhat less effective, because you'd be balancing the core focus of this exercise alongside trying to draw the correct ellipses, which inevitably would only give you so much mental energy and focus to commit towards the exercise's intent.

I do hope that your reasoning for going freehand was due to the absence of any other option. I will of course not comment on any issues that arise from the inconsistency of the freehanded ellipses, as that would not be particularly useful.

Anyway! Starting with the structural aspect of your wheels, you've done fairly well. I can see that you've been mindful of including a larger ellipse in the center of your wheel to create a sort of curving profile, which helps to promote the impression of an inflated tire, rather than the impression that it's solid all the way through. You've also handled the spokes in your rims/hub caps well, not just establishing the outward face, but also giving the structure side planes so they can be properly interpreted as solid, 3D structures.

One thing I would advise against however is the tendency to fill in the empty space between the spokes with solid black, as you did in cases like wheel 15. Remember that in this course, our filled areas of solid black should be reserved only for cast shadows, where the shape of the resulting shadow is designed based on our understanding of how the form casting it relates in 3D space to the surface upon which it is cast.

Carrying onto the textural aspect of this challenge, I can see that you did run into the same trap that most students fall into at this point. While it isn't entirely by design per se, it is something I've come to expect, and is tied into the purpose this challenge serves. Basically, given how far removed we are from Lesson 2, it's very normal for students to end up forgetting about the principles outlined there in regards to explicit vs. implicit markmaking, so this challenge serves as a reminder that one might want to review those concepts and notes before finishing up the course.

I can see that you did play with approaching the tire tread textures with a variety of strategies. There were the cases like wheels 18 and 20 where you simply applied constructional, explicit markmaking to build out each textural form with outlines. While this can be sufficient to handle a wheel floating in the void, it unfortunately does result in a lot of contrast when dealing with a full vehicle construction, creating focal points and drawing the viewer's eye whether you want it to or not. This doesn't give us many options in terms of controlling how the viewer engages with the drawing.

Working with implicit markmaking instead - in other words, not drawing the textural forms but only drawing the shadows they cast on their surroundings - allows us to change how heavy we decide to make the texture (in terms of more ink vs less ink) according to our needs, without changing the nature of the texture being depicted. You can see what I mean here in this example of bush viper scales.

There were other cases where you did try and work with more filled areas of solid black, but in them you tended not to actually work with cast shadows. Instead, we primarily saw cases where you would fill in the side planes of your textural forms, as we see in cases like wheel 23 and 22. This is more akin to form shading, where the orientation of a surface dictates whether it be darker or lighter, and where the whole surface gets filled in (instead of the shadow being its own shape, designed based on the spatial relationships it's trying to define).

This can be more noticeable in textures with very large, prominent textural forms - like the big chunky treads we see in some tires, but those with shallower grooves can have their own challenges. Often times students will see these and look at the grooves themselves as being the textural form in question. As a result, they focus on it, and fill those grooves in entirely, rather than thinking about the actual forms that are present on the surface of the object. This is also an issue we can run into in textures that have holes in them.

Instead, as shown here, we have to focus on the walls surrounding the grooves, as they are the structures that will cast shadows into the vacant space. Honestly the difference isn't always that noticeable in the result - but it's about the way we think about them, which extends to how we think about other situations where the difference in outcome is more significant. As with everything we practice throughout this course, it comes down to whether or not we're thinking about 3D forms, as they exist in 3D space, or if we're just taking shortcuts to draw what we see without the necessary intermediary step of understanding how that translates into three dimensions. You can read more about this in these reminders from Lesson 2.

As these kinds of issues are largely expected, I do not hold students back over them - so I will be marking this challenge as complete. Just be sure to review the texture material so you apply it more correctly going forward, and in your own practice.