Honestly, as a whole these are very well done. There's one little issue I'll talk about regarding your chunkier tire treads, but as a whole I am very pleased. As to the ellipse guide's limitations, technically they're meant to be sold in full sets which provide a wide range of ellipses, but for the purposes of the last leg of this course, students generally make do well enough with the "master" ellipse templates, which as you noted don't have as many size options. At the end of the day you cooould always shell out a hundred bucks for a full set, but it's probably not going to be worth it unless you expect to use it outside of this course.

So, looking at your wheels, I'm very happy with how conscientious you've been about their construction. You handle the various rims/hubcaps very well, maintaining the same level of solidity - something that can be quite tricky with things like spokes at that scale (like number 14).

When it comes to capturing your textures, you clearly were cognizant of the principles covered back in Lesson 2, and I can see it throughout how you've managed your linework, and worked implicitly in many key areas. But there's two key areas where you didn't quite manage it as well - number 5 and 6. These are the cases where you've got chunkier treads, but unfortunately the way they were drawn made them appear a little flat.

Between them there's two issues. In number 5, there's too much reliance on outlining, creating a very even border around each chunk, which in turn makes it seem as though it has no depth. In number 6, there's a more notable shift from one end to the other, but instead of focusing on capturing cast shadows, you've just filled in the side plane of each given textural chunk. As shown here, leaving that side plane empty and capturing the shadow it casts on its surroundings will have a better overall impact, establishing not only that chunk as a clearly 3D form (especially if the silhouette is defined more intentionally, which can be a bit tricky at that scale), but also establishing the relationship between that form and the structure to which it attaches.

So! Just be sure to keep that in mind. Aside from that, you're doing great. I'll go ahead and mark this challenge as complete.