Jumping right in with the structural aspect of the challenge, overall you've handled this pretty well. You've made solid use of your ellipse guide to build out the body of your wheels, most of which have been fairly cylindrical and rigid (as demanded by the individual reference images you worked from), though when required you included a solid widening through the midsection, which helps to create the impression that the tire is inflated, and would land with a bounce rather than a heavy thud.

One point I did notice was that - and this is somewhat understandable given the small space you had to work with - the spokes of your wheels' rims tended to be drawn a little less intentionally. When working in small spaces, it does require us to be much more patient and careful with every stroke - and despite this, working small can leave us predisposed to being a little sloppier and less concerned with the intentionality of our markmaking.

Another point related to this is that for those spokes, each of which feature different planes for the various sides of that structure, I noticed cases where, as shown here, the wrong side plane was drawn as being visible to the viewer.

Continuing onto the textural aspect of the challenge, this is where the challenge becomes a bit of an intentional trap for students. Being as far removed from Lesson 2 as we are at this point, it's very common for students to forget the concepts we discuss there. Most run into this problem, either in partially remembering that we work with filled areas of solid black to convey texture but not remembering specifically how (and not reviewing the material to refresh that memory), or in entirely forgetting about it and opting to try and approach the texture entirely through explicit markmaking in the form of outlines, as you've done here.

When it comes to texture specifically - at least, how we handle it in this course, which is very specific to this course - we are ultimately looking at the same kind of problem that the course as a whole explores: spatial reasoning. We imply the marks we draw (you can refer to the implicit vs explicit markmaking section for more specific information on this) by drawing the shadows our textural forms cast on their surroundings, not by drawing the forms themselves (in terms of outlining them, or otherwise drawing anything about the form itself). It's the shape of the shadow itself, which is designed based on our understanding of the relationship in 3D space between the form casting it and the surface receiving it. And so, as stressed in these reminders, in this course we're never just drawing what we see. We're looking at our references, and understanding what they tell us about the forms in question, and then deciding on how to convey the relationships between them in space.

The reason we use implicit markmaking instead of explicit is fairly simple, although it's not always obvious. For example, looking at any of your wheels like those on this page, they all look excellent floating in the void, all full of detail. But when any one of them becomes part of an existing drawing, all of that packed detail can actually work against you by drawing the viewer's eye to it whether you want it to or not. This interferes with our ability to control composition (which is all about dictating how the viewer experiences a piece, what they look at and in which order), which while outside of the scope of this course, is still something I want to give students the tools to engage with more easily.

Explicit markmaking basically locks us into an agreement with the viewer: whatever is drawn is present, and whatever has not been drawn, is not present. And therefore to convey each textural form, we have to declare its presence explicitly. Implicit markmaking on the other hand gives us more freedom by disconnecting the marks we draw from the specifics of what is present.

Now the reason we leave this as a trap rather than reminding students in the instructions for the challenge is that lessons learned this way (specifically that there may be things we've forgotten about and might need to review) tend to stick a bit better, and make a larger impact. I still won't be assigning revisions, and will be marking this challenge as complete - just be sure to review the material relating to texture (starting with the reminders here), and also take some time to reflect on whether there might be other concepts from the course that have also fallen through the cracks, so you can review them as well before continuing on.