I came across a tutorial a while back where the author shows how to model a truck using primatives and dynamesh he also shows how to build a mag wheel. I cant find it again for the life of me and was hoping someone could point me to it.
I'm not sure if your referring to my thread, or not, but I did build a truck using only Zbrush. I didn't make a tutorial about it but there are a lot of post showing the progress and some discussions on what I did to get to that point, at the time. I did do a tutorial for using shadowbox to make some parts for the bicycle I built with Zbrush. Most of the stuff I've built has been hard surface projects and many of those are vehicles. Here's the link to my thread. I hope you find something that will help you out in there.
I never made a tutorial about making mag wheels either but I think Gary Komar did in his thread. Gary also makes a lot of hard surface projects and he also has a lot of vehicle type projects. Here's the link to a couple of Gary's thread.
You may also want to take a look at Pixolator's two videos below where he shows the 'making of' a motorcycle. It's not a tutorial but if you watch closely you can get a lot of insight about how he works to get the parts made.
It stuck in my brain because it's exactly what I was looking for a few weeks back...
Ezra, those are also some really good links! Your bike is great - I tried a motorcycle but started pulling out my hair once I got to all of the mechanisms! Gonna pore over your thread and Pixolator's video to get "back in gear" LOL