One thing about this challenge is that it's actually a trap. By the time most students reach this point, they're so far separated from the old annals of Lesson 2 that they have a tendency to forget all about the principles of how to approach drawing texture, of implicit markmaking, and the importance of cast shadows.

Fortunately, it seems you're not most students.

Starting with your construction, you're doing great - you're making excellent use of the arrangement of your ellipses (good on you for picking up an ellipse guide by the way) to achieve not a standard stiff cylinder, but a form that actually feels inflated as a tire should. You achieved this in how many ellipses you used, and how they varied in scale (allowing for a more tapered end on each side).

One thing I did notice however was that you did seem to use the same degree for the ellipses - this may simply have been a limitation of your ellipse guide, which you certainly wouldn't be penalized for, but just for the sake of covering everything, make sure that in the future you do increase the degree of your ellipses as you move farther away from the viewer (as explained in the Lesson 1 ellipses video, which was updated back in the spring and features a little prop-based demonstration to make sense of the concept).

You've also shown a great deal of care and patience in constructing the rims/spokes of these wheels, and generally handled their spacing in a reliable, regular fashion.

Moving onto the whole textural trap I alluded to at the beginning, I can see that as you pushed through the set, you struggled initially with how exactly to apply the principles from Lesson 2 here, but you picked up on how to do it pretty quickly. Tires with shallower grooves are pretty easy, but when we get into "chunkier" tire textures like number 4, things start to get a little trickier.

Your attempt for number 4 was actually really close - you made excellent use of cast shadows, and you left the interior of your textural forms empty. The only mistake was that in outlining each textural form's silhouette, you separated them from the surface they were meant to rest upon, making them separate constructed forms rather than part of a single cohesive texture.

You corrected this in cases like 20, 22, 23 and 25 though, where you allowed the cast shadows to stand on their own, and only outlined where the textural forms pushed past the silhouette of the wheel itself. As a whole, you've shown a lot of thought and consideration to how to tackle these, and by the end of it you definitely nailed it.

Very nice work. I'll go ahead and mark this challenge as complete.