12" Pneumatic Wheels

[fredericks]

Is there any restrictions to a larger wheel? If not, does someone have a source for purchasing?

[CalTran]

No restrictions on wheel size, besides the general frame perimeter / robot height, etc. rules. As far as sourcing, a simple Google search yields multiple results. As well, try looking at Harbor Freight or McMaster, but be warned for most wheels at this size, you'll have to create custom hubs for them.