Starting off with the construction of your wheels, you've done a pretty fantastic job here. Not only were you mindful and meticulous in employing as many ellipses as were needed to capture the gently "inflated" appearance of each wheel - which we achieve by creating a more nuanced, beveled structure with more ellipses, either through the midsection or towards the ends - but you also took considerable care in constructing the rims/spokes/hubcaps of each wheel. This can be quite tricky, especially when it comes to spacing them out correctly.

Now, the other component of this challenge is where it becomes a bit of a trap. See - for most students who reach this stage of the course, it's been a very long time since they'd last looked at the concepts covered in regards to texture way back in Lesson 2. As a result, they tend to forget about how to think about approaching texture, and what exactly might constitute a texture to begin with. And as such, when tackling the tire treads here - which being made up of a bunch of little forms that adhere to the surface of a larger object are certainly textures - many students end up approaching them just as they would anything else, through explicit markmaking and constructional techniques.

For the most part, you did indeed fall into this trap. There are some places where you kind of picked up on the idea that drawing and outlining every little form in its entirety might not work out so well (causing you to put down more partial marks in numbers 9 and 10, which is definitely a step in the right direction), but throughout the majority of these you ended up outlining most of your forms.

The reason this isn't ideal is that it basically locks you into having to draw each and every tread "chunk" in its entirety, thus creating the potential of a pretty high-contrast, visually noisy element. It's not such a big deal when the wheels are presented individually, but if they were to be part of a larger drawing, they'd create a focal point, drawing the viewer's attention whether you mean them to or not. Working with implicit markmaking, where every mark is itself just the shadow cast by the textural form (which itself can be made larger or smaller based on shifting the lighting rather than actually changing what is actually present in the scene) allows us far more control over whether or not we want the wheel to be a focal point at all. This can be seen in the various ways this bush viper scale texture can be depicted.

Now for the most part, one can get away with using more explicit mark making when the textural forms are smaller - like when you've got tire treads made up more of grooves or very small bumps. It's when they get chunkier that our approaches stand out more. Still, the key point to always remember is that however we make our marks, we need to be thinking of each textural form individually. When a tire's tread pattern is made up primarily of shallower grooves, it can be easy to shift into drawing those grooves as lines, and instead of thinking in terms of drawing the positive space (the tread forms themselves), we end up drawing the negative space (the gaps and grooves), resulting in marks that do not actually imply the presence of the forms themselves, and lack the kind of nuance that give such a texture a sense of depth and tangibility.

So! Be sure to give Lesson 2's texture section another glance to refresh your memory before moving forward. You're still good to consider this challenge complete however, and you've still done a pretty good job with it for the most part.