You will never like your own work if the final product is not what your mind's eye envisioned. Your own artistic integrity is the true worth of anything you ever create.
Because you feel you can't successfully make wheels does not mean you alter your vision and 'make do' with an alternative. You stop and cross that hurdle. I suggest you study some galleries for wheels. d-p's and Mykola's gallery is full cars that will help out. Circle tutorials can be found in the tutorials page. You can even make a whole new pixel that used loads of circles to learn from. Once you feel comfortable come back to this.

ps: that's the nice version ;)