Rubber wheels will flat spot if you don't use it very regularly and will cause trouble with 600lbs+. Stick with the steel wheels but don't get them larger diameter, it will make access under a crossmember impossible. Best upgrade to a HF cherry picker is a pneumatic/hydraulic ram. They're about $80 and are worth every penny. I used some HF 10" pneumatic casters on my cherry picker that I use in my shop lot. I can lift and move almost anything and the tires really help across rough ground where the small steelies would not turn at all. I'm tired of replacing HF junk tires so I think I'm going to get solid rubber tires from Northern Tool.