Jumping right in with the structural aspect of the challenge, you've by and alrge done a great job. There are a couple things I want to call out, but they're fairly minor, and for the most part I'm quite pleased with how this aspect of the challenge turned out. Looking at the core structure of the wheels, it's clear you've made good use of your ellipse guides - which, from the looks of it it seems you went all in and bought a full set of them, which must have been quite expensive.

One significant point I do look for is whether students are, when drawing the spokes of their wheel's rims, going beyond just drawing the outward face of the structure, but rather also considering their side planes in order to give them greater solidity and thickness. I'm pleased to see that you did this generally, although there were two minor points where it was somewhat overlooked.

One of those is the hub cap on this wheel, where the little holes aren't given any thickness to them. Not a big concern, but still something that was overlooked. The other is with your bike wheel, which is a somewhat unique circumstance given the fact that those spokes are actually extremely thin. They're thin enough that if we're focusing on accuracy, lines are the correct choice. But, if we're focusing on conveying the illusion of solidity, lines don't actually do much to imply or describe the presence of an actual form. At the very least, we'd want a shape - something with an outline containing some amount of internal space - to achieve that. And so, instead of drawing each spoke with a single line, doubling them up to contain just a little bit of width/thickness will help reinforce the sense that the structure is solid and three dimensional, even though it will make it a little thicker than the object we're referencing.

Mind you, this is more a consideration for how we approach the problem in this course. Outside of the course, going with a straight line may be the better choice. Here however, our focus is above all else on conveying solidity and understanding the things we draw as forms that exist in 3D space - and beyond that, understanding how those 3D forms relate to one another within that space. So for our purposes here, this strategy works best.

Moving onto the textural aspect of the challenge, this element of the exercise is something of a trap. It's very, very common for students to largely forget about the principles of implicit markmaking introduced in Lesson 2, and to simply not review them to consider how to approach the textures of the tire treads in this exercise, and so the trap serves as something of a reminder that this course covers an enormous amount of information, and going back to refresh one's memory is entirely expected. Furthermore, it's meant to suggest that perhaps there could be other things the student allowed to slip through the cracks, and to consider what that might be and attempt to address it before moving forward to complete the last lesson of the course.

You certainly have fallen into that trap - generally speaking you've approached each of your tire's tread textures through explicit markmaking. That is to say, you approached it in the same constructional manner as the core structure of the wheels, building out every textural form. While this results in wheels that look quite good in isolation, as soon as they get thrown into an illustration as part of a vehicle, those wheels will create strong focal points that draw the viewer's eye due to the density of detail present there.

Implicit markmaking on the other hand - that is, where what we draw are the shadows that the forms cast upon their surroundings, not the forms themselves - so not entirely dissimilarly to what you did here (although I would strongly recommend getting a brush pen or a thicker fineliner to fill those shadows in), just without first drawing those forms themselves. That of course makes it a hell of a lot more challenging, as you're holding that 3D structure in your head while trying to decide how to draw the shadow it casts.

These shadow shapes are designed based on our understanding of the relationship between the form casting them and the surface receiving them - this means it hinges on the spatial reasoning this course focuses so heavily upon, which is understandably lacking back in Lesson 2 where the textural concepts are introduced. They're introduced there along with the form intersections with the intent of framing the context in which those spatial reasoning skills are developed.

While this trap was intentional, and so we do not assign revisions on that basis, you should absolutely go back and review the texture material to ensure you're equipped to apply those concepts going forward. In particular, start with these reminders.