Before we get started, I wanted to take a moment to address the tools you're using. It's clear that you're using an ellipse guide, which is great - though the kinds of ellipse guides students generally have access to will fall into 2 distinct categories.

The most common is the "master ellipse template", which is basically one sheet that has ellipses of different sizes, split across a few different degrees. These aren't too expensive, and are definitely adequate for the challenge, though students do often get frustrated with the fact that they're generally limited to smaller ellipses. The other would be a full set of ellipse guides, which are generally quite expensive (upwards of a hundred dollars) and consist of many different templates, covering a wide range of ellipses, with many sizes across many different degrees. I show both types in this video from Lesson 0.

Now my concern here is that based on the size of your wheels, you're definitely not using a master ellipse template (since the ellipses are very large). That said, I'm noticing a lot of areas where you freehanded a curve (like the lines down the middle of number 11) instead of using an ellipse guide - which suggests that you didn't have one that would do the trick. This makes me wonder if you perhaps picked up one sheet from a larger ellipse guide, rather than a master ellipse template, or that you may be working with an otherwise partial set.

This doesn't impact the validity of your work, of course - just wanted to make sure you've got access to the right tools.

Anyway! Starting with the structural aspect of your wheels here, I'm pleased to see that you're constructing most of your wheels with a nice bump through the profile, which helps to capture the sense of "inflation" - where the wheel's not going to land on the ground with a heavy thunk, but rather it'll bounce due to the tire. 19 and 24 are examples where this wasn't the case, although I assume this was intentional, and that the particular reference may have specifically been straight through the middle. That said, if you can, do be sure to always establish those in-between cross-sections with a complete ellipse, ideally drawn with an ellipse guide. Of course this would not be expected from someone working with a more limited master ellipse template, so that's more of a recommendation if the option is available to you, as it'll help flesh out the whole a bit better, as the freehanded curves tend to go a bit awry, like what we see in number 23.

When it comes to the rims/spokes, I did notice some differences between the wheels, in terms of how you handled the way in which those spokes connect to the outer portion of the wheel. I'm very pleased to see that you're defining both the outward face as well as the side planes, which helps to make those structures appear more three dimensional, but be sure to establish that connection as you do in 23 and 22 (as shown here) and not as you did in number 15, which as shown here has that side plane completely flatten out and connect in the same way as the front face.

Now, continuing onto the textural aspect of the challenge, this is where we start to get into a bit of a trap. It's very common to find that being as far removed from Lesson 2 and its textural concepts as we are, so close to the end of the course, students are more likely to forget a lot of what we covered back there. It does appear to be the same with you, as your attempts at tackling the tire tread textures appear to be exclusively using explicit markmaking techniques. As discussed back in Lesson 2, when we capture textures, we want to be drawing the shadows those textural forms cast, rather than outlining the textural forms themselves. This generally means observing our reference carefully - not to transfer what we see directly to the drawing, but rather to help us understand how those textural forms sit in space. It is that understanding we then leverage to specifically design each individual cast shadow shape. I go into more detail on this here in these notes.

To that point, I am noticing that you do have a tendency to oversimplify aspects of your textures here as well, relying more on repeating patterns and memory, rather than specifically capturing what is present - this usually comes from simply not giving yourself enough time to continually observe and study your reference between each mark you put down. You can read more about the unreliability of memory here in these notes.

It can definitely be easier to fall into this manner of thinking when dealing with tire treads that are made up of shallow grooves, where the difference between explicit outlines and implicit shadows becomes harder to identify. It comes down at this point more to how we think about the things we're drawing. When we're dealing with textures made up of grooves or even holes, we end up thinking more about the grooves themselves as being the textural forms. Of course, they're not - they're an absence of form. Rather, it's the walls around those grooves that are casting the shadows. They're the textural forms. This diagram elaborates upon this point.

Now, I am still going to be marking this challenge as complete. Because it's an intentional trap, a sort of reminder for students to review that material they'd forgotten about, it is at least somewhat expected that most students will fall into it. I do strongly recommend that you revisit that material however. In addition to this, note that Lesson 7 is the most demanding lesson of this course, and it requires a lot of time be invested into each individual drawing - in the realm of several hours at minimum, though some students have ended up putting 10 hours and more into a single construction. Be mindful of that, so that you are not caught unawares.

Oh, also if you want to show me a picture of the ellipse guide(s) you're working with, I can tell you if there's any issues.