Congrats on finishing the wheel challenge! I'll do my best to give you advice so that you can improve.

Starting with the structural part of the challenge, most of your wheels are pretty well done given they look like they were done freehand. You've also handled the spokes of your rims quite well in most cases, establishing not only the outward face of the spokes but also their side planes, so as to establish them as solid forms. However for 18, 14 and 2 they end up feeling flat because you only drew the front plane while ignoring the side planes. If possible try to always make sure to establish them as solid forms. Furthermore on some of your wheels (24, 18, 17, 14, 16, 15) the side planes have only been defined with one ellipse instead of several https://drawabox.com/lesson/25wheels/1/step3 which makes the wheels look flat, although I can understand why you wouldn't want to go over it several times freehand as that might mess it all up which is why an ellipse guide is highly recommended. Also for number 20, make sure you are applying the ghosting method and drawing confidently from the shoulder especially since you aren't using an ellipse guide. Now although I say you haven't used an ellipse guide, some of your ellipses look perfect while others don't which makes this somewhat conflicting so I'm curious as to how you drew them. But if you don't have an ellipse guide I strongly recommend you get one. The cheapest ones are master ellipse templates so look for those if you are going to buy one.

Also the areas of solid black on the rims + spokes is actually form shading and should be avoided as seen on 21, 8 and 6. Solid black should only be reserved for cast shadows

For the textural component you've fallen into the trap that uncomfortable has designed. As this lesson is far removed from lesson 2 most students end up forgetting the textural aspect of drawabox (which is implicit markmaking) and fall back into explicit mark making. The reason that explicit markmaking is not always an effective tool for every task is that it locks us into a very dense amount of visual detail (which can be seen on wheel number 10). This can be fine if we're looking at wheels floating in the void, but when we use them as part of a larger vehicle, they become focal points, drawing the viewer's eye to them whether we want them to or not. This severely limits our ability to guide the viewer's eyes through a piece.

Conversely, implicit markmaking allows us to alter how we convey the texture (in terms of how densely we pack in that information) without changing the nature of the texture itself, which we can see here on this example of bush viper scales.

Another point to consider however is that this can be pretty easily detected with very chunky textures, but when we're dealing with much shallower grooves, the distinction between doing it correctly and incorrectly can be pretty slight. Hell, the actual visual result can be the exact same, but the manner we think about it can make the difference.

In effect, when dealing with tires with shallow grooves - or any texture with holes in it - students can be prone to viewing the groove itself as being the "textural form" in question. So, they focus on drawing it, filling in the groove with black and moving on. But of course, the groove isn't a form - it's an absence of form. Instead, the forms in question are the walls along the sides of the groove, casting shadows upon one another, and upon the floor of the groove itself. This diagram demonstrates this concept visually, to make it somewhat easier to understand.

Lastly, I wanted to give you a couple additional diagrams - more focused on how we think through the texture analysis exercise in Lesson 2 - but still applicable here since it's all about understanding how to approach identifying our forms without drawing them, so we can imply them with cast shadows alone.

• Firstly, this diagram (or alternatively this one which is essentially the same, just framed a little differently in case it makes more sense) demonstrates how texture requires us to think about the relationship between the light source and each individual form.

• And secondly, this diagram shows, using a texture of melted wax, how we can think about first identifying the forms themselves, and then designing the shadows they'll cast.

However even if you fell for the trap that does not mean that you have to do revisions. Even if there are numerous problems with the structural component of your wheels I think it's just due to do a lack of ellipse guide. If you do end up getting one I would visit wheels again and maybe do around 5. Also be sure to review the texture material, especially these notes.

Good luck for lesson 7!