Starting with the wheel constructions themselves, you've done a fantastic job. I can see that you didn't skimp on your ellipses, using a bunch of them to capture a lot more of the nuanced curvature of these inflated forms, and it has certainly paid off. The results feel quite solid, and it carries over into the spokes/rims, where you've similarly paid attention to their properties in all three dimensions. The spokes definitely aren't easy - spacing them out properly while maintaining both the front planes and the internal side planes of those structures can be quite challenging, though you managed it well.

The other major point we explore with this challenge comes down to the application of Lesson 2's textural principles. It's pretty common for students, who at this point are so far separated from Lesson 2, to outright forget the points discussed back then about implicit markmaking and such. While this is less of a concern with tires with simpler tread (especially the ones with narrower, shallower grooves), those with chunkier elements to their tread patterns are harder to get around, and many will outline them completely, employing explicit drawing techniques.

I am quite pleased that you appear to have remembered those points, and revisited them. That's made clear by your heavy use of specific, intentionally designed, filled shadow shapes, especially when getting into those chunkier treads. There is however a bit of an issue that I'm noticing that I would like to address. As shown here, it's not entirely clear whether you're placing those solid black shapes on the side plane of the tread chunk itself, or if it's sitting on the adjacent surface. Or rather, some of them are less clear than others, with those along the top specifically being more loosely drawn. Those towards the middle are definitely better, although maintaining a consistent light source and ensuring the shadows are being cast in the same direction will also help.

At the end of the day, the specific and intentional design of those cast shadow shapes is incredibly important. I do think that's something you understand, and something that you have tried to apply - often to fairly good results - but it's still something that will require further and continued honing and practice.

So! I'll go ahead and mark this challenge as complete. You've done well, so keep up the good work.