When it comes to the construction of your wheels, you've done a fantastic job. Your forms feel solid and it's clear that you've put a great deal of time and effort into building out all of the elements of your rims/spokes. I'm honestly kind of puzzled as to how you went about drawing the wheels - enough of them are uneven enough to suggest that you freehanded them, but enough of them are really solidly executed that it kind of blows my mind to think that you did. Initially it crossed my mind that maybe you were able to acquire the biggest ellipse guide set known to man, but... that's probably not the case.

Now, while there's a lot that you did well, there are still a few things that I'd like to point out:

• The first of these is that it's pretty clear that you were working with an underdrawing, which you'd then trace back over to darken some lines over others. This likely did play a role in your ability to execute those massive ellipses, although it really doesn't discount the amount of time and effort you put in. Still, even though we've loosened the reins on which tools we're allowed to use, I would still like you to adhere to the same principles of the course. That is, avoiding tracing back over lines, avoiding putting marks down hesitantly, and reserving the "line weight" pass purely to clarifying overlaps between forms in specific, localized areas - not to trace back over large areas. Note that back in Lesson 6, I mentioned where I allowed the use of ballpoint, that you should be picking one or the other, rather than using a ballpoint to make an underdrawing. That applies across the board, including this challenge and lesson 7.

• The other point I wanted to call out is more of a trap that I laid out, that the vast majority of students fall into. In your case though, it's a little different. Tire treads, especially those with big chunky sections, fall under the category of texture. After all, they're made up of small forms that sit along the surface of a larger form. That means that in order to draw them, you should be employing the principles covered back in Lesson 2's texture section - focusing particularly on implicit drawing techniques. It's very clear that while you did delve into excellent use of cast shadows, it was only after you first constructed those textural forms in their entirety. As a result, you boxed yourself into explicit markmaking (which is what construction falls under). The textural concepts of this course are difficult - they ask you to hold the nature of a given form in your mind, without actually drawing it on the page, and considering what kind of shadow it'll cast on its surroundings. Constructing those forms ahead of time will yield a better immediate result, but we're not after pretty pictures here. Opening yourself up to making mistakes, to making some drawings that end up coming out badly, is what will allow you to develop those skills.

Now, as I said - most people make that blunder, although in your case you did still get into cast shadows (once the construction was set out), and you did apply them correctly there. Just be sure to continue pushing yourself to try to lay out texture without the training wheels on.

Anyway, you are doing quite well overall. I'll go ahead and mark this challenge as complete.