CGCookie Model A Wheel Exercise

This one was an excellent lesson in modelling, had a lot of difficulties,.. it took me many days trying and trying. For example the tire treads, pfff. Kept modelling them starting with a plane and then adding loop cuts, etc.., it simply didn't worked, but after watching a tutorial I learned I had to start building up from one simple vertex! Still battle a bit with the array and curve modifiers, as you probably can see on my rim. Its still a lo-o-ong way to master the modelling in Blender. Thanks and greetings.