To start, don't worry about the size - it's vastly more important that you use the ellipse guide which forced you to work smaller, simply because of how it takes a lot of the uncertainty and variability of freehanded ellipses out of the equation. Working smaller obviously has its own struggles, many of which you did encounter here, but I've critiqued a fair number of these with students taking either avenue, and those sticking to their itty bitty master ellipse templates have been better off for it.

Jumping right into your wheels, I can definitely see a good deal of improvement over the set. Towards the beginning you were definitely still getting a feel for how to use your ellipse guides (resulting in a lot of wheels that seemed to have a larger far end, or at least one equal in size (which technically due to perspective would mean it's physically larger to compensate for foreshortening). I'm glad to see that you did improve upon this pretty quickly, and got in the swing of constructing solid wheels with nice bevels on each end to produce a sort of "inflated" impression.

I'm also pleased with your attention to construction (that is, the specific 3D nature) of the rims themselves. Sometimes students will get a little too lax with this, forgetting about defining things like separate side and top planes. So, as a whole your construction is quite solidly done across the set.

Now, construction is only half of the challenge. It is at this point that I spring a trap. Many students find that when they're this far along through the course, they've forgotten about the textural principles we introduced back in Lesson 2 - those about implicit markmaking, and using cast shadows of textural forms. So, I find that tire treads are an excellent chance to trip them up a little bit, and refresh their memory.

Since tire treads are basically an arrangement of forms along the surface of a smooth cylinder, they are most definitely a good candidate for being drawn as texture. And in fact, it actually can become necessary to do so if your tire tread is especially dense, resulting in an unintentional focal point from all the visual noise on your wheel. This is most applicable with the treads that have larger chunks sticking out (like 19 and 20), where you end up with a lot of linework packed across a small space. Using the implicit markmaking techniques discussed back in Lesson 2 allows us to reduce the overall contrast and noise of the area, and regain control over whether or not we create a focal point there. This can also be seen in this example - it's a bush viper's scales, rather than a tire, but it still conveys how the density of the texture can be controlled.

I did notice where on 20 you started filling in the side planes of the big tread chunks - this is going in the right direction, but not quite the same as drawing the shadow the form itself casts. The shadow is actually a new shape that helps define the relationship between the form casting it, and the surface receiving it, as shown here.

Lastly, in cases like 22, here you've drawn out what is effectively a pattern of criss-crossing lines along the surface of the wheel, and so it looks more like that pattern has been painted, flat, on the surface of the cylinder. The key is in focusing on the textural form that is casting each shadow. Not of the grooves, but the actual form around them.

Now, these are common mistakes students generally make, and certainly nothing to hold you back over. Just take it as an opportunity to go back and review the texture section from Lesson 2, so it's fresh in your mind when you step through the doors at the end of Lesson 7.