Starting with the construction aspect of these wheels, it's very common for students to initially feel limited and restricted by the ellipse guide - but honestly, once you get the hang of them they can be quite feasible, at least for what we ask of them here. Sure, it results in smaller wheels, but honestly you've done a great job here of not only laying out enough ellipses to achieve a nice, "inflated" structure (rather than just a simple stiff cylinder) but also in capturing the wide variety of rims/spokes across your wheels to considerable levels of detail.

I mean, they're all good, but some of them like 21 really stand out in terms of just how much you've been able to cram into such a small space.

That actually does bring me to one little concern - I can't help but feel that you may have been either working with a pen that was particularly thick, or that you were pressing a little hard as you drew. One of the most challenging things involved in working at such a small scale is simply that the thickness of our lines can be very difficult to work with, making it especially important that we both continue to work with the usual 0.5mm pen (which you may well be doing), and that we take care to control our pressure.

When using a tool like a ruler or an ellipse guide, it is easy to press harder than we intend to, so that may simply be what happened. Either way, reducing that thickness can help to alleviate some of the difficulties of working at such a small scale.

Now, the second part of this challenge is actually a bit of a trap. For most students hitting this stage in the course, it has been a very long time since they went through Lesson 2, and so many students have a tendency to forget about the principles of how to approach texture. And the tire treads we deal with here are, in the fact that they're made up of a lot of little forms that sit along the surface of a larger structure, just that: texture.

This means that our focus shifts to capturing the specific textural forms through implicit markmaking - that is, instead of outlining or drawing those forms themselves, we focus on understanding the manner in which those forms sit in space, and establish their relationships with their surroundings by drawing the shadows they cast.

Looking at your work, you have definitely fallen into the trap pretty hard, in that you relied quite heavily on explicitly outlining your textural forms rather than focusing on the shadows they'd cast. As a result, your tire treads did end up coming out to be quite dense and noisy, with no recourse for you to lighten them up. Meaning that if these wheels were part of a larger drawing, they would inevitably become their own focal points, drawing the viewer's attention instead of simply being supporting material.

In using cast shadows rather than outlines, we're given more control just how much ink is used to capture a specific element (and therefore how much contrast it produces and how much attention it draws), without changing the nature of what is being communicated. Meaning, we can still tell the viewer that a given surface is covered in textural forms, we just don't necessarily have to draw each and every one. A good way to illustrate this is with this example - not of a tire, but of a bush viper's scales. Note how we can control just how much light hits the surface, and therefore what kind of shadows those textural forms will cast.

Now one positive point is that the majority of your tire textures did recognize the individual forms that are arranged across the tire's surface, which is obviously a big step towards doing this correctly. It's just a matter of changing the way in which they're conveyed to the viewer. There is one however - number 22 - where instead of thinking of the tire tread texture as a series of textural forms, you instead treated it more as a pattern. In drawing criss-crossing lines, you're not capturing the actual interaction between distinct forms and the surfaces around them. Rather, it comes off more as a smooth surface that has stripes painted across it.

So! Obviously you fell in my little trap (as many people do), but that's pretty normal. You've still done a great job, there's simply some material you probably will want to revise before moving forwards. I'm still going to mark this challenge as complete, so you're free to move on.