I agree it would be an improvement if the Tennis Tutor machines had an expanding handle for taller people, but if you are going from the parking lot to the court, the wheels seems plenty smooth.
I've called Tennis Tutor regarding repairs and information on (or not on) their site. They purposely do not put detailed specs on their site as most people don't need such information. As far as parts list or instructions they tell me, and I agree, that they prefer to deal with the customer directly so they can properly troubleshoot a machine. It makes sense when they say if customers attempt to self-diagnose their machine and order parts it often leads to confusion, improper parts ordered and more work. This is why Tennis Tutor is so admired for their customer service. They know how to take care of their machines and their customers. I know mine is humming along just fine!