I definitely think shifting to your ellipse guide made a big difference - primarily in allowing you to worry less about the mechanics of putting your marks down on the page, so you could put more of your mental resources to addressing the main concerns of the challenge. You definitely achieve varying levels of success when freehanding as well, and some of them are notably well done, but with the first few where you were trying to figure out how to deal with all your ellipses, it's pretty clear that other elements ended up taking a hit as a result - especially when it comes to the structural solidity of things like the rims' spokes. One such example is in how the spokes in number 7 don't connect to the outer rim of the structure in a consistent manner. Some appear to connect to the back of the rim, some connect only to the front. This one connects appropriately with the front face connecting to the front portion of the rim, and the side plane being arranged appropriately, but the mark I added in red is missing, so the viewer isn't provided with enough information to understand how it connects along the side plane. As a whole though, these structural elements certainly do improve as you have less on your plate to worry about, and as you're able to start out with cleaner ellipses. It's pretty common that I see students being more inclined to think through every mark they put down when their drawing is already clean - but as things start to go awry, they tend to allow more issues to slip through.

Now, given that you've looked at other submissions and feedback, you probably know that this challenge serves a purpose as a trap for those who've forgotten about the principles of explicit vs. implicit markmaking as introduced in Lesson 2. It's fair to say that you definitely performed better in this regard compared to most, although there are a few points I still want to draw to your attention.

One circumstance that students tend to struggle with is textures that have holes or grooves. Because the words we use to describe the elements of the texture (hole, groove, crack, etc.) reference the negative spaces and not the actual textural forms. This causes them to think that these elements are the textural forms, causing them to fill them in with black. We can see an example of this in number 8.

Instead, as explained in this diagram, the textural forms we must pay attention to are instead the walls that surround these grooves, which cast shadows upon each other and the floor at the bottom of the groove.

The other point I wanted to mention is that when it comes down to thinking through how our textural forms are arranged along the surface of the tire, it takes... a lot of time. Impatience is really our biggest enemy here, especially when we have textures that are densely packed with textural forms. This can tempt us to relying more on more generalized patterns, or an amount of randomness when building up those textures. We can see an example of this in number 13, where the shadows drawn tend not to align to one another, and instead the texture gets compressed in some areas, and swollen in others.

Ultimately the core of it comes down to giving ourselves as much time as we need for a given problem, not as much time as we are comfortable investing. Sometimes a task will simply take more time than you have that day, and will need to be spread out. Giving ourselves more time means having more time to focus on each individual textural form one at a time, and assess what forms exist around it. This is in effect a matter of taking on a smaller task (only worrying about a few forms/surfaces at a time), rather than trying to balance everything together, and put down a few quick marks.

There are definitely cases where you've handled this better - 16 for instance is following a more structured approach to lay out where those forms will sit. It's not ideal, because it still puts marks down on the page (for texture we want to avoid putting any major marks down, but individual little points/dots are fine because they tend to have much less of a footprint on the page, and don't draw as much attention), but as a whole this is still better than working randomly, or completely outlining/constructing those forms in their entirety.

All in all, you're definitely showing that throughout this challenge you've been aware of what you need to focus on, and have pushed yourself to work in those directions, so I am by and large quite pleased with your work. No doubt some of it comes from having looked at those other critiques, but there really isn't anything wrong with that.

So! I'll go ahead and mark this challenge as complete, and will leave you to continue developing your level of comfort with these concepts.